FUEL SYSTEM - Marinemechanic.com
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1. 5 17 Removal 5 17 Installation 5B 18 Exploded View 5B 24 Disassembly 5B 25 Cleaning and Inspection 5B 34 Reassembly 5B 35 NOTICE For information and procedures on trouble shooting refer to Section 1C Index siad 5B WEBER 4 BARREL CARBURETOR 90 823224 2 796 Identification E VY AEN PS A 70389 Weber Identification Number Location Replacement Parts Warning Electrical ignition and fuel system components on your MerCruiser are designed and manufac tured to comply with U S Coast Guard Rules and Regulations to minimize risks of fire and explo sion Use of replacement electrical ignition or fuel system components which do not comply with these rules and regulations could result in a fire or explosion hazard and should be avoided Index 90 823224 2 796 Torque Specifications Fastener Location Ib Carburetor To Manifold Fuel Line To Carburetor Tools Part Number Universal Carburetor 91 36392 Gauge Universal Carburetor Stand Torx Screwdriver 15 20 25 Obtain Locally TORX SCREWDRIVERS Weber carburetors will have a star shaped socket in the head of some screws TORX screwdriver must be used on this type of screw The sizes used are number2. 90 823224 2 796 Important Service Information Weber Carburetor Adjustable Accelerator Pump The accelerator pump lever on Weber Carburetors has three holes in it The closest hole to the lever s pivot point is the richest the second hole is leaner and the hole furthest away is the leanest All produc tion carbs have the pump rod installed in the closest richest hole If you are having a rich bog on accel eration move the rod to the second or third hole Weber put the three holes in the lever so the amount of fuel delivered by the accelerator pump could be changed 10472 a Rich b Lean c Leaner Index 90 823224 2 796 Hard Starting If a hard starting condition exists after engine has not been operated for a period of time proceed with the following 1 Before starting engine remove flame arrestor then operate throttle to see if choke closes 2 If choke is stuck open check choke stove link rod and choke linkage on both sides of carburetor for cause of sticking Possible paint or interference to rod or linkage Ifchoke plate does not close tight step 2 or 3 then choke link rod will have to be bent to make it shorter so it will close choke plate completely gt 73716 Bend Here To Shorten 4 After installing ensure that the rod does not rub against stove cover or carburetor throughout its travel WEBER 4 BARREL CARBURETOR 5 7 Carburetor Meter
3. Rod Accelerator Pump 40 Wire Clip 41 Wire Clip 42 Gasket 43 Screw 4 44 Gasket 2 45 Jet Secondary Fuel 2 46 Secondary Air Valve and Weight Assembly 47 Plunger Washer 48 Plunger Guide 49 Accelerator Pump 50 Spring Accelerator Pump 51 Float Bowl Body Carburetor Bottom Index 90 823224 2 796 Disassembly The following is a step by step procedure for com pletely overhauling carburetor after removal from en gine In many cases however complete overhaul is not necessary and in these cases only the steps re quired to repair the carburetor malfunction should be performed Read the instructions carefully to prevent doing unnecessary steps IMPORTANT Before performing any service on carburetor it is essential that carburetor be placed in a holding fixture to prevent possible damage to throttle valves 1 Remove wire clip to disconnect accelerator pump linkage a Wire Clip b Accelerator Pump Linkage Rod WEBER 4 BARREL CARBURETOR 5B 25 2 Remove wire clip to disconnect choke plate link age 70392 Wire Clip b Choke Plate Linkage Rod NOTE Do not remove vacuum hose if not servicing diaphragm 3 Disconnect vacuum hose from choke pull off dia Vacuum Hose b Choke Pull Off Diaphragm Index 5B 26 WEBER 4 BARREL CARBURETOR 4 Remove screws from choke pull off diaphragm bracket to disengage choke pull off linkage NOTE
4. Side 107 in 3310 805341 9776S 3310 805341 l 9776SA 110 In 101 in 16 7147 Pink 3310 806971 9776SB Note1 This model carburetor had staggered primary jets MIE 8 2L Bluewater MIE 8 2L Bluewater 3310 818659 1071 098 in 16 6542 Pink 9772 MIE 7 4L Bluewater WFB Index siia 90 823224 2 796 WEBER 4 BARREL CARBURETOR 5B 3 101 in 095 in 092 in 5000 ft 1525 m 5000 9000 ft 9000 ft 2745 m 3310 818659A 098 in Port 092 in Port 089 in Port 7 4L Bravo 9772 077 In Starboard 074 in Starboard 071 in Starboard 7 4L Bravo 0 Stock 3 Metering ed 2 Kit Electric Choke 9780S Metering ed Rod See Note 7 4L Bravo Three 3310 805569A Serial OF 838819 9777 edn ween to OF800699 454 Magnum mr EE 454 Magnum 331 NES otock 3 Step e Kit Electric Choke 9779S Metering Rods 2 re Note 3310 818659A 098 in Port 092 in Port 089 in Port 7 4L Inboard 9772 077 In Starboard 074 in Starboard 071 in Starboard Automatic Choke 0 3310 805341 8 2L Inboard 9776 Automatic Choke ES u 0 806791A 8 2L Inboard 3310 806971A Electric Choke 9776SB NOTE Elevation Kit Number 1 Part Number 809615 Jet Changes for Altitude Change Only Secondary Jets Automatic Choke 0 on Electric Choke 7 4L Bravo Three 3310 806755 Stock 3 Step Kit Electric Choke 9779S Metering Rod See Note e 805341 502 Magnum e Automatic Chok
5. TO ALLOW FOR CORRECTIONS OR ADDITIONS AT LATER DATE ju ul WEBER 4 BARREL CARBURETOR 5B 45
6. fuel line and carburetor attaching hard 7 ware Remove carburetor and throttle bracket Discard old gasket from carburetor 8 71173 71172 a Fuel Line b Attaching Hardware Throttle Bracket Index 5B 18 WEBER 4 BARREL CARBURETOR Remove adaptor wedge plate if so equipped from manifold and discard old gasket Place a clean cloth over intake manifold open ings IMPORTANT Covering intake manifold prevents entry of dirt or foreign material through open ings Installation 1 Place appropriate new gasket on intake man ifold If so equipped install adaptor or wedge plate de pending on model Place appropriate new gasket on top 90 823224 2 796 IMPORTANT Carburetor is calibrated for use with an adaptor or 15 wedge plate if the model was nally so equipped Be certain to install adaptor or 15 wedge plate if it was present upon disassembly 7 4L BRAVO MIE 7 4L HURTH DOWN ANGLE VELVET DRIVE BORG WARNER 5000 AND VELVET DRIVE V DRIVE TRANSMISSIONS MCM 7 4L PT BRAVO THREE Index JU TE 90 823224 2 796 WEBER 4 BARREL CARBURETOR 5B 19 MCM 454 MAGNUM 00 00 74937 502 MAGNUM 2 gt e e Co 74394 e Index 5B 20 WEBER 4 BARREL CARBURETOR 90 823 224 2 796 MIE 8 2L VELVET DRIVE BORG WARNER V DRIVE AND HURTH DOWN ANGLE TRANSMISSIONS Index 10 90 823224
7. matched sets as noted during disassembly 20 Install appropriate inlet needles into inlet seats 70446 a Inlet Needle s b Seat s IMPORTANT If using existing floats be sure to reinstall them on the same side as removed Index 5B 40 WEBER 4 BARREL CARBURETOR 21 Install floats using hinge pins 70400 a Pin s b Floats s 22 Carefully lower top of carburetor onto bottom part 70399 90 823224 2 796 23 Ensure gasket is properly positioned between the two parts and secure the top to bottom with screws nine total Tighten securely a Screw s 24 Install metering rod springs into each metering rod hole Be certain to install the appropriate col or spring refer to Specifications a Spring s IMPORTANT If using existing metering rods be sure that they are reinstalled in the same side from which removed during disassembly Index 90 823224 2 796 25 Carefully install metering rod assemblies in the appropriate holes Push down lightly on metering rods to ensure that plunger will spring up and down QS SAN 20 PS 70396 a Metering Rod Assembly s IMPORTANT Some carburetors are equipped with air deflectors that are attached to the screw that holds down the metering rod covers Be sure to reinstall the deflectors if your model carbure tor requires them 26 Position metering rod cove
8. the jumper wire is left in place the ignition module will operate in the Base Timing Mode This means that the additional timing advance fea tures would not be functioning 7 Remove the jumper wire from the timing terminal 90 823224 2 796 Repair 4 Disconnect retaining clip and choke linkage rod NOTICE Refer to Precautions in this section BEFORE proceeding Removal IMPORTANT Carburetor malfunctions are in many cases caused by the presence of dirt wa ter or other foreign matter in carburetor To aid in diagnosis carefully remove carburetor from en gine without draining fuel from bowl Contents of fuel bowl may then be inspected for contamina tion as carburetor is disassembled 71096 1 Turn off fuel supply at fuel tank Retaining Clip Linkage Rod O f 2 Hemove carburetor cover Remove crankcase ventilation hoses from flame arrestor then re move flame arrestor 5 Disconnect fuel pump sight tube and fuel line IMPORTANT Place a clean cloth in bores of car buretor to prevent dirt and foreign material from falling into bores 3 Disconnect throttle cable attaching hardware from throttle bracket and throttle lever anchor studs Remove throttle cable 71171 a Fuel Pump Sight Tube b Fuel Line a Throttle Cable b Bracket Attaching Hardware d Anchor Studs Index UTE 90 823224 2 796 WEBER 4 BARREL CARBURETOR 5B 17 6 Remove
9. with two screws Tighten securely 70455 a Gasket Primary Venturi Cluster 13 Install the primary venturi clusters a Screws Two Each Side b Primary Venturi Cluster s 15 Install the accelerator pump spring into bottom half of carburetor 70454 o ey ceti EP Gasket Primary Venturi Cluster One Not N Visible In This View b Primary Venturi Cluster 70451 a Accelerator Pump Spring b Carburetor Bottom Index 5B 38 WEBER 4 BARREL CARBURETOR 90 823224 2 796 16 Install accelerator pump in top of carburetor housing after placing washer and guide in posi tion 70450 a Accelerator Pump b Plunger Guide c Plunger Washer Not Visible In This View 17 Connect accelerator pump lever to pump rod us ing the S link Secure pump lever with pivot screw Tighten securely Check to ensure lever actuates the accelerator pump 70449 Accelerator Pump Lever Accelerator Pump S Link Retainer Screw QOO 9 Index 90 823224 2 796 18 Install gasket on top of carburetor mE e le 70448 a Gasket 19 Install inlet filter in bottom of inlet seat Install inlet seat with gasket in place Tighten securely SIN N NS o0 D 70447 Gasket Inlet Filter oO O 9 WEBER 4 BARREL CARBURETOR 5B 39 IMPORTANT If using existing needles and seats be sure to reinstall them as
10. 10 90 823224 2 796 WEBER 4 BARREL CARBURETOR 5B 23 Exploded View Weber Carburetor 90 823224 2 796 5 7 C 1777 MANN WA X je lt gt O i 1 v Ae x 9 UC Py Me EN n NT 5 2 al E amp N D l i gt S B UUN 9609696 9 OOO OO oc O m CC lt lt st CC x m N m LO 1 Air Deflector 2 2 Screw 2 3 Cover Metering Rod 2 4 Metering Rod Assembly 2 5 Spring Metering Rod 2 6 Fuel Inlet Fitting 7 Sealing Washer 8 Screw 9 Linkage Rod Choke Pull Off 10 Screw 11 Air Horn Carburetor Top 12 Filter Fuel Inlet 2 13 Gasket 2 14 Seat Fuel Inlet 2 15 Needle Valve Fuel Inlet 2 16 Pin 2 17 Float 2 18 Secondary Venturi Cluster 2 19 Baffle Plate Float Bowl 2 20 Screw 4 21 Primary Venturi Cluster 2 22 Gasket 2 23 Jet Primary Fuel 2 24 Screw 2 25 Fuel Pump Injector Housing 26 Gasket 27 Check Weight or Check Spring if So Equipped 28 Check Ball 29 Screw 30 Diaphragm Choke Pull Off 31 Vacuum Hose 32 Idle Mixture Screw 2 33 Spring Idle Mixture Screw 2 34 Gasket Carburetor Base 35 Linkage Rod Choke Plate 36 S Link 37 Accelerator Pump Lever 38 Screw 39 Linkage
11. 2 796 WEBER 4 BARREL CARBURETOR 5B 21 3 Install carburetor and throttle bracket with attach ing hardware Torque fasteners to 132 Ib in 15 N m 71173 Throttle Bracket Not Visible In This View b Attaching Hardware 71172 Throttle Bracket b Attaching Hardware Index 5B 22 WEBER 4 BARREL CARBURETOR 4 Install fuel line To prevent over tightening hold fuel inlet filter nut with suitable wrench and tight en fuel line connector securely 71173 Fuel Line b Fuel Inlet Filter Nut 5 Connect fuel pump sight tube and fuel line 71171 a Fuel Pump Sight Tube b Fuel Line 90 823224 2 796 6 Connect choke linkage rod and install retaining clip 71096 Clip Linkage Rod O 7 Refer to Section 2 Install and adjust throttle cable following instructions appropriate to your power package Install flame arrestor and tighten nut securely 9 Reconnect battery cables to battery by first in stalling positive battery cable to positive bat tery terminal Tighten clamp securely Then in stall negative battery cable to negative battery terminal Tighten clamp securely 10 Turn on fuel supply at fuel tank 11 Start engine and check for gasoline leaks If leaks exist STOP ENGINE IMMEDIATELY and re check connections 12 Adjust idle speed and idle mixture as previously outlined under Adjustments Index
12. Depending on amount of service required it may not be necessary to remove diaphragm and bracket a Screws b Linkage Rod IMPORTANT Metering rods should always be re moved before separating top and bottom halves of carburetor 90 823224 2 796 5 Loosen not necessary to remove depending on 7 Remove metering rod springs amount of service required metering rod cover screws Turn cover or remove to expose meter IMPORTANT Metering rod springs are color Ing rod coded and should not be interchanged with other carburetors 71095 a Screws a Spring s b Metering Rod Cover s Air Deflectors If Equipped oppa 8 Remove nine screws to separate top and bottom IMPORTANT Be careful not to mix metering rods when removing them 6 Carefully lift metering rod assemblies straight out a Screw s a Metering Rod Assembly s Index 90 823224 2 796 WEBER 4 BARREL CARBURETOR 5B 27 9 Carefully lift off carburetor top and disconnect 11 Remove inlet needle from seat choke linkage IMPORTANT Be careful not to mix up inlet needles and seats after removal 70399 10 Slide pin out to remove the float 70401 IMPORTANT Be careful not to mix up floats after removal 70400 a Pin s b Float s 70446 a Inlets Needle s b Seat s Index 5B 28 WEBER 4 BARREL CARBURETOR 90 823224 2 796 12 Remove seat gask
13. FUEL SYSTEM WEBER 4 BARREL CARBURETOR Index Table of Contents Page Identification 5B 1 Replacement Parts Warning 5 1 Torque Specifications 5B 1 l EEE A 5 1 Specifications 5B 2 Carburetor 58 2 MIE Carburetor 5B 3 Jet Changes for Altitude Change Only Secondary Jets 5B 4 MCM Carburetor Adjustment Specifications 5B 5 MIE Carburetor Adjustment Specifications 5B 5 Description 5B 6 Precautions E 5B 6 Important Service Information 5B 7 Weber Carburetor Adjustable Accelerator Pump 5B 7 Hard Starting 5B 7 Carburetor Metering Rod And Jet Indentification 5B 8 Maintenance 5B 9 Flame Arrestor 5B 9 Fuel Filter 5B 10 Adjustments 5B 11 Accelerator Pump 5B 11 Choke Pull Off 5B 12 Float Drop 58 12 58 13 Idle Speed and Mixture Adjustments 5B 14 Thunderbolt IV Equipped Engines 5B 14 Thunderbolt V Equipped Engines 5B 16 Repair
14. Index 5B 34 WEBER 4 BARREL CARBURETOR IMPORTANT DO NOT use a wire or drill to clean jets passages or tubes in carburetor as this may enlarge orifices and seriously affect carbu retor calibration 3 Wipe all parts that cannot be cleaned in immer sion cleaner with a clean dry cloth 4 Carefully inspect all carburetor parts for damage or wear pay particular attention to the following a Idle mixture screws Replace if damaged or worn b Fuel inlet needle valve and seat Replace with new needle and seat if worn or damaged c Casting surfaces Inspect accelerator pump plunger well for scoring or deposits Replace worn or corroded components d All linkage rods and levers Replace if worn or damaged e Accelerator pump and plunger parts Re place pump and parts if worn or damaged f Floatassembly and hinge pin Float weight of each should be the same Replace either if fuel can be heard inside when shaken Check hinge pin and holes for wear Replace components if worn or defective g Throttle valves and shafts Check for bind ing through entire operating range making sure valves open and close completely or for looseness in carburetor body IMPORTANT DO NOT remove throttle valves If any of the throttle parts or float bowl carburetor body shaft bores are found to be worn or dam aged carburetor replacement is required h Choke valve and shaft lever assembly Check shaft and lever for exces
15. Primary Venturi Cluster 20 Remove two screws that secure secondary ven turi clusters 70456 a Screw s Two Each Side b Secondary Venturi Cluster s Index 90 823224 2 796 21 Remove secondary venturi cluster by lifting it straight up 70457 22 Remove gaskets from beneath secondary ventu ri clusters us 70458 Gasket Secondary Venturi Cluster WEBER 4 BARREL CARBURETOR 58 31 23 Remove secondary air valve and weight assem 25 Remove pump jet housing bly by lifting it straight out a Pump Jet Housing 26 Remove gasket from beneath pump jet housing a Secondary Air Valve And Weight Assembly 24 Remove two screws that secure pump jet hous ing 70462 a Gasket Pump Jet Housing 27 Remove check ball and check weight 70460 check ball and check spring from hole beneath a Screw s pump jet housing b Pump Jet Housing Index 5B 32 WEBER 4 BARREL CARBURETOR IMPORTANT If your carburetor had a ball and weight combination replace with ball and weight If your carburetor used a ball and spring combination replace with ball and spring a Check Ball b Check Weight Check Spring 28 Remove float bowl plates if necessary a Baffle Plate Index 90 823224 2 796 IMPORTANT Do not mix up the primary and sec ondary jets Make note of the jet sizes and their location before removal to
16. be certain that during reassembly they are installed in the carburetor side from which they were removed NOTE If jets are difficult to remove place a screw driver with the correct wiath in the jet slot and lightly tap the end of the screwdriver with a hammer 29 Remove primary and secondary jets 70466 a Primary Fuel Jet b Secondary Fuel Jet IMPORTANT Before removing mixture screws check and note the number of turns from the fully seated position Also do not mix up the two screws WEBER 4 BARREL CARBURETOR 58 33 30 Remove mixture screws 70467 Idle Mixture Screw Spring Idle Mixture Screw O Cleaning and Inspection CAUTION Rubber plastic parts pump plungers or dia phragms cannot be immersed in carburetor cleaner CAUTION Avoid damage to carburetor Do not leave carbu retor in immersion type cleaner for more than two hours IMPORTANT Do not immerse metering rod springs in carburetor cleaner the color if not natural metal may be removed Clean separately as needed 1 Clean metal carburetor parts in a commercial im mersion type cleaner until all deposits have been removed Follow manufacturer s instruc tions of cleaner being used for proper cleaning and rinsing procedures CAUTION Avoid personal injury Always wear safety glasses when using compressed air 2 Blow out passages with compressed air Do not drill through passages
17. d weight If your carburetor used a ball and spring combination replace with ball and spring 70464 b Check Ball Check Weight d Check Spring WEBER 4 BARREL CARBURETOR 5B 35 5 Position pump jet housing gasket 7 Install two screws that secure pump jet housing Tighten securely c c b NE n oL 70462 4 lt Ni a Gasket Pump Jet Housing 6 Install pump jet housing a Screws b Pump Jet Housing 8 Install the secondary air valve and weight assem bly a Pump Jet Housing a Secondary Air Valve And Weight Assembly Index siad 5B 36 WEBER 4 BARREL CARBURETOR 90 823224 2 796 IMPORTANT Before installing venturi clusters it 10 Install the secondary venturi clusters is important to note which clusters were equipped with a distribution tab This distribu tion tab arrangement varies from one carburetor to another a Secondary Venturi Cluster 11 Secure each cluster with two screws Tighten se Distribution Tab s Location And Total Number Vary 9 Position the secondary venturi cluster gaskets 2 7 TFLS 70456 7 lt S a Screws Two On Each Side b Secondary Venturi Cluster s a Gasket Secondary Venturi Cluster Index d TE 90 823224 2 796 WEBER 4 BARREL CARBURETOR 5B 37 12 Position the primary venturi cluster gaskets 14 Secure each cluster
18. e 3310 OS E uM 101 in 095 in 092 in 502 Magnum 3310 806971A Electric Choke 9776SB 7 4L Inboard m 0 Stock 3 Step E Kit Electric Choke 9780S Metering Rod See Note SA Elevation kit Number 2 454 Magnum Only Part Number 809620 Index 5B 4 WEBER 4 BARREL CARBURETOR 90 823224 2 796 UNIT OF MEASUREMENT In mm ALL MEASUREMENTS 1 64 In 0 4 mm MCM Carburetor Adjustment Specifications Engine Model 7 4L 7 4L Bravo Three 454 Bravo 502 Bravo Carburetor Manufacturer 9772 9777 9776 9776SA Float Level 1 9 32 in 33 Float Drop 2 in 51 mm Top Of Rod Even With Bottom Of Lever Hole 2 Preliminary Mixture Idle 1 1 4 Turns screw Setting MIE Carburetor Adjustment Specifications Engine Mode Carburetor Manufacturer Number 9772 9780S 9774 9776 9776S 9776SB Float Level 1 9 32 in 33 mm Float Drop 2 in 51 mm Pump Rod Hole Location Third Hole From End Accelerator Pump 7 16 in 11 mm Choke Pull Off 15 64 in 6 mm Choke Coil Rod Top Of Rod Even With Bottom Of Lever Hole Preliminary Mixture Idle 1 1 4 Turns Screw Setting 1 Measured from top of carburetor to bottom of S link Remove choke rod from lever hole Choke held closed and choke rod pushed down with top edge of rod even with bottom edge of hole Index siia 90 823224 2 796 WEBER 4 BARREL CARBURETOR 5B 5 Description Weber WFB carburetor is unique in design as the main body and flange ar
19. e cast as a one piece unit This along with the bowl cover make up the two piece construction which is made of light durable aluminum to dissipate heat There are two separate float circuits Each float cir cuit supplies fuel to a primary low speed circuit and a primary and secondary high speed circuit The bowls are vented to the inside of the air horn A con necting vent passage effects a balance of the air pressure between the two bowls The float needle valves are installed at an angle to provide the best possible seating action on the needles This provides better needle response to float movement also The high speed circuits use staged step up rods in the main metering jets to control the amount of fuel admitted to the nozzles The position of the step up rod is controlled by manifold vacuum applied to the vacuum piston A primary air bleed located in the venturi cluster pre vents a rich condition or bog as the high speed circuit is reactivated after deceleration Small L shaped metal tabs called distribution tab s are attached to some venturi clusters and protrude into the air stream at the proper location to aid distribution of fuel on selected applications Precautions Always disconnect battery cables from battery BEFORE working on fuel system to prevent fire or explosion Be careful when cleaning flame arrestor and crankcase ventilation hose gasoline is extreme ly flammable and highly explosive und
20. e of float as shown It must be set at 1 9 32 in 33 Vas 1 70468 a Float Level Measurement b Gasket Index 90 823224 2 796 WEBER 4 BARREL CARBURETOR 5B 13 Idle Speed and Mixture IMPORTANT Do not turn idle mixture screws tightly against seat as damage to seat and or Adjustments needle may result Thunderbolt IV Equipped Engines PRELIMINARY IDLE SPEED AND MIXTURE Initial start settings are given following Make final ad justment with engine running refer to Final ldle opeed and Mixture 1 Turn idle speed screw until it contacts throttle lever a Idle Mixture Screws Needles 10474 a Idle Speed Screw b Throttle Lever Contact Point 2 Turnidle mixture screws needles in clockwise until LIGHTLY seated then back out 1 1 4 turns Index siad 5B 14 WEBER 4 BARREL CARBURETOR 90 823224 2 796 FINAL IDLE SPEED AND MIXTURE IMPORTANT Boat MUST BE in the water and en gine at normal operating temperature to accu rately check and adjust idle speed and mixture Carburetor should be set so that engine idles as smoothly as possible with boat in the water engine normal operating temperature and drive unit in for ward gear To adjust idle soeed and mixture proceed as follows IMPORTANT DO NOT attempt to compensate for other engine problems incorrect ignition timing faulty ignition components low compression vacuum leaks etc with carburetor adju
21. ead 13 PUR WHT wire to a good en gine ground This locks the ignition module into the Base Timing Mode 2 Adjust idle mixture following the procedure in the appropriate engine service manual 3 Remove the jumper wire from the timing terminal ADJUSTING ENGINE IDLE SPEED This procedure should be done with boat in the water drive unit in neutral and engine at normal operating temperature Refer to the Operation and Mainte nance Manual for the correct idle speed 1 Disconnect the throttle cable from carburetor Index 5B 16 WEBER 4 BARREL CARBURETOR IMPORTANT In order to properly set idle speed the ignition module MUST BE locked in the Base Timing Mode This is necessary because of the Idle Speed Control feature that exists in the ignition module See information on the previous pages about this feature 2 Connect a shop tachometer to engine 3 Using a jumper wire connect the ignition system timing lead 13 PUR WHT wire to a good en gine ground This locks the ignition module into the Base Timing Mode 4 Start engine and allow it to reach normal operat ing temperature Place the remote control lever in forward gear idle position 5 Adjust idle speed to recommended RPM Stop engine Readjust cable barrel and reinstall the throttle IMPORTANT Be sure to disconnect the jumper wire from the ignition system test terminal before attempting to resume normal operations If
22. er certain conditions Be sure that ignition key is OFF DO NOT smoke or allow sources of spark or open flame in area when cleaning flame arrestor and crankcase ventilation hose Index 5B 6 WEBER 4 BARREL CARBURETOR Be careful when changing fuel system compo nents gasoline is extremely flammable and high ly explosive under certain conditions Be sure that ignition key is OFF DO NOT smoke or allow sources of spark or open flame in area while changing fuel filter Wipe up any spilled fuel im mediately Fuel Supply Connections Avoid gasoline fire or explosion Improper instal lation of brass fittings or plugs into fuel pump or fuel filter base can crack casting and or cause a fuel leak e Apply 592 Loctite Pipe Sealant with Teflon to threads of brass fitting or plug DO NOT USE TEFLON TAPE Thread brass fitting or plug into fuel pump or fuel filter base until finger tight Tighten fitting or plug an additional 1 3 4 to 2 1 4 turns using a wrench DO NOT OVER TIGHTEN Install fuel line To prevent over tightening hold brass fitting with suitable wrench and tighten fuel line connectors securely Check for fuel leaks Make sure no fuel leaks exist before closing en gine hatch A CAUTION DO NOT operate engine without cooling water being supplied to water pickup holes in gear housing or water pickup inlet or water pump im peller will be damaged and subsequent overheat ing damage to engine may result
23. et and inlet filter IMPORTANT Be careful not to mix up seats after SIN N m removal 70447 Seat b Gasket c Inlet Filter 13 Remove gasket from top of carburetor 70448 a Gasket Index 90 823224 2 796 14 Remove accelerator pump lever 70449 a Accelerator Pump b Accelerator Pump Lever c Retaining Screw 15 Remove accelerator pump NE GIU Gz In 70450 a Accelerator Pump b Plunger Guide c Plunger Washer Not Visible In This View WEBER 4 BARREL CARBURETOR 5 29 16 Remove accelerator pump spring from bottom 17 Remove two screws that secure primary venturi half of carburetor cluster lt Ue CEU ON SSR fe CEI Os p pape gt 7 N ie 210 L i ty FT eA A es F eM i 3 WR 7 70451 a Screw s Two On Each Side a Accelerator Pump Spring b Primary Venturi Cluster s b Carburetor Bottom 18 Remove primary venturi cluster by lifting straight IMPORTANT Before removing venturi clusters it is important to note which clusters are equipped with a distribution tab This distribution tab ar rangement varies from one carburetor to anoth er 70454 a Distribution Tab s Location And Total Number May Vary Index siad 5B 30 WEBER 4 BARREL CARBURETOR 90 823224 2 796 19 Remove gasket from beneath venturi cluster 70455 a Gasket
24. ing Rod And Jet Indentification METERING ASSEMBLY The metering rod assemblies are different in the fol lowing ways uj Three Step NV o QT Jat Two Step T VV Piston Metering Rod Spring Jet Piston Cover Index 5B 8 WEBER 4 BARREL CARBURETOR METERING JETS The metering jets in this carburetor are taller than the jets in a standard carburetor Three Step Two Step o 5 Three Step Metering Rod b Two Step Metering Rod METERING ROD HAS THREE STEPS VS TWO Three Step A 4 Two Step D A 4 73724 PISTON SHAPE IS DIFFERENT AND HAS A SECOND SPRING Three Step 73730 Two Step 73727 90 823224 2 796 PISTON ASSEMBLY COVER IS HIGHER ELECTRIC CHOKE The electric choke should be set with marks aligned 74104 Maintenance 73736 Flame Arrestor PISTON BORE HAS A STEP ON THREE STEP MODEL 73737 Index 90 823224 2 796 a b NOTICE Refer to Precautions in this section BEFORE proceeding 5 Remove in the following order Nut Sealing washer Carburetor cover Crankcase ventilation hoses from flame ar restor and rocker arm covers Flame arrestor 6 Clean and inspect Clean flame arrestor in solvent and blow dry with compressed air Clean crankcase ventilation hoses Inspect crankcase ventilation hoses for cracks or deterioration and rep
25. lace if neces sary EE WEBER 4 BARREL CARBURETOR 5B 9 7 Install in the following order Fuel Filter a Flame arrestor NOTICE b Crankcase ventilation hoses to flame arres Refer to Precautions in this section tor and rocker arm covers BEFORE proceeding Carburetor cover Carburetor inlet fuel filter is installed in bottom side of fuel inlet seat in the carburetor top Refer to Disas e Nut tighten securely sembly and Reassembly to service Sealing washer 11372 70447 Flame Arrestor with Carburetor Cover Typical Fuel Inlet Seat with Gasket Nut b Fuel Inlet Filter Sealing Washer Carburetor Cover Sta Strap Crankcase Cover Crankcase Ventilation Hose Flame Arrestor oro Ando Index 5B 10 WEBER 4 BARREL CARBURETOR Adjustments NOTICE Refer to Precautions in this section BEFORE proceeding Accelerator Pump IMPORTANT Refer to Important Service Infor mation in this section regarding the three ac celerator pump linkage holes and placement of linkage rod 1 Back out idle speed screw until it no longer con tacts throttle lever a Idle Speed Screw b Throttle Lever Contact Point 70473 Idle Speed Screw b Throttle Lever Index 90 823224 2 796 Close throttle valves completely Accelerator pump 15 set at 7 1 6 11 mm which is measured from the carburetor top to the bottom of the S li
26. nk as shown d ei D A TAC 4 Adjustment of accelerator pump is done by ing the linkage as necessary to achieve the prop er dimension as stated above 10472 70473 WEBER 4 BARREL CARBURETOR 5B 11 Choke Pull Off 2 Bendchoke pull off linkage to achieve setting giv mE en in Step 1 1 Choke pull off is checked by holding in on vacu um diaphragm and attempting to close choke plate The gap between the plate and housing is to be set at15 64 in 6 mm a 70471 a linkage Bend Float Drop 1 Measure float drop from bottom side of carbure tor top to toe of float lowest part as shown It must be set at 2 in 51 mm 70471 a Vacuum Diaphragm b Choke Plate Housing d Gap Measurement a Drop Measurement 2 f float drop is not correct hold hinge pin firmly and bend tab shown as needed Index TIT 5B 12 WEBER 4 BARREL CARBURETOR 90 823224 2 796 IMPORTANT Do not put pressure on fuel needle 2 If float level requires adjustment hold hinge pin valve and seat while bending tab or damage may firmly and bend float arm shown as needed result IMPORTANT Do not put pressure on fuel needle valve and seat while bending tab or damage may result a Float Float Level Tab Bend b Tab Bend Float Level 1 Measure float level from bottom side of carbure tor top with gasket in place to to
27. rs and air deflectors if equipped over metering rods and install screws Tighten securely 71095 a Screws b Metering Cover s Air Deflectors If Equipped WEBER 4 BARREL CARBURETOR 58 41 27 Reconnect choke pull off linkage to carburetor 29 Reconnect choke plate linkage Secure with wire Reinstall choke pull off diaphragm Secure with clip two screws and tighten securely a Screw s b linkage Rod 28 Reconnect vacuum hose to choke pull off dia 70391 Choke Plate Linkage Rod b Wire Clip a Vacuum Hose Index 5B 42 WEBER 4 BARREL CARBURETOR 90 823224 2 796 30 Reconnect accelerator pump linkage rod to hole in accelerator pump lever where originally con nected or refer to Important Service Information in this section for information regarding adjust ment Accelerator pump linkage adjustment should be checked at this time refer to Adjust ments Accelerator Pump as previously out lined Secure using wire clip Lm we 70390 a Accelerator Pump Linkage Rod b Wire Clip 31 Refer to Installation and install carburetor Index 10 90 823224 2 796 WEBER 4 BARREL CARBURETOR 58 43 THIS PAGE IS INTENTIONALLY BLANK TO ALLOW FOR CORRECTIONS OR ADDITIONS AT A LATER DATE Index 5B 44 WEBER 4 BARREL CARBURETOR 90 823224 2 796 Index 90 823224 2 796 THIS PAGE IS INTENTIONALLY BLANK
28. s 15 20 and 25 WEBER 4 BARREL CARBURETOR 5 1 Specifications MCM Carburetor Mercury Meterin Metering Carb Number Primary Secondary pen d 9 Rod Spring engine mode Type Manufacturer Jet Size Jet Size Number Number Color MCM 7 4L SN OF352105 A 107 16 6542 and Below 7 4L SN OF352106 and uot 104 in 16 757347 Above WFB MCM 7 4L Bravo Three SN OF070156 and Above MCM 7 4L Bravo Three SN OF070155 and Below A 107 in 166542 Pink 3310 806755 9779 97795 106 in 16 757347 Green 3310 805341 9776 3310 806791 110 in 101 in 16 7147 Pink 9776S 1 7 4L Engines with the following serial numbers may have staggered jets in the main and or secondary jets They should be changed to jets listed above for that respective carburetor MCM Stern Drive serial numbers OF022828 and below MIE Inboard serial number OD857999 and below MCM 7 4L MCM 454 Magnum SN OF304599 and below MCM 454 Magnum SN OF305000 and 2 lt 454 502 Index 5B 2 WEBER 4 BARREL CARBURETOR 90 823224 2 796 Specification continued MIE Carburetor Mercury Carb Number Primary Secondary Type Manufacturer Jet Size Jet Size Number Metering oe Rod Number Engine Model Spring Color 3310 806969 8 Port Side 3310 817693 104 in 9774 Starboard 098 in 16 6542 Pink See Note 1
29. sive loose ness in air horn Check choke valve and shaft lever assembly for binding through en tire operating range Air horn assembly must be replaced if choke valve and shaft lever are worn 5 Check that choke pull off diaphragm plunger re tracts when vacuum is applied to unit and that it holds vacuum plunger remains seated if vacuum is maintained 90 823224 2 796 Reassembly 1 Install mixture screws needles with springs in place Turn idle mixture screws in clockwise un til LIGHTLY seated then back out one and quar ter 1 1 4 turns if previous settings were not noted on disassembly IMPORTANT Do not turn idle mixture screws tightly against seat as damage to seat and or needle may result 70467 a Idle Mixture Screw b Spring Idle Mixture Screw 2 Install the primary and secondary jets Tighten only till snug IMPORTANT Be sure that primary and secondary jets are installed in the appropriate location Be sure that the size matches the same size re corded during disassembly ol WC a Primary Fuel Jet b Secondary Fuel Jet Index 90 823224 2 796 3 Install the float bowl baffle plates if previously removed 70465 c Baffle Plate 4 Into bore beneath pump jet housing location in stall check ball and then check weight or if so equipped check ball and check spring IMPORTANT If your carburetor had a ball and weight combination replace with ball an
30. stments This will only cover the problem which must be corrected if engine is to achieve maximum fuel economy and performance 1 Connect a shop tachometer to engine IMPORTANT DO NOT turn idle mixture screws needles tightly into seat as damage to needle and or seat may result 2 If anew or rebuilt carburetor has been installed turn each idle mixture screw until it LIGHTLY con tacts seat if not already accomplished then back out 1 1 4 turns This will provide a sufficient setting to allow starting the engine 3 Start engine and run at 1500 RPM until engine reaches normal operating temperature DO NOT leave helm unattended while performing idle speed and mixture adjustments following BE CAREFUL NOT TO ACCIDENTALLY ACCELERATE ENGINE WHILE PERFORMING ADJUSTMENTS Index 90 823224 2 796 4 With boat in open water place remote control in forward gear idle position 5 Disconnect throttle cable barrel from anchor stud BE SURE NOT TO LOSE SPACER ON AN CHOR STUD 6 Adjust idle speed adjustment screw to obtain specified idle RPM Refer to Section 1B Tune Up Specifications charts NOTE Idle soeed must be at specified RPM or less Or engine will be operating on the off idle circuit Mix ture screw adjustments will be ineffective if this condition exists 7 With engine running at or just below specified idle RPM adjust idle mixture screws as follows a Turn idle mixture needle in clockwise un
31. til the engine speed begins to decrease due to LEAN mixture b Turnsame idle mixture screw outward coun terclockwise until the engine speed begins to decrease due to a RICH mixture c Turn screw in to a point between these two extremes to obtain maximum engine smooth ness and RPM d Repeat procedure with other mixture screw e Readjust idle speed adjusting screw if nec essary to obtain specified idle RPM 8 Place remote control in neutral Turn ignition OFF 9 Accelerator pump linkage should be rechecked at this time Refer to Steps 3 and 4 of Adjust ments Accelerator Pump as previously out lined and verify pump is set at 7 16 in 11mm as specified 10 Refer to SECTION 2 Install and adjust throttle cable following instructions appropriate to your power package WEBER 4 BARREL CARBURETOR 5B 15 Thunderbolt V Equipped Engines ADJUSTING IDLE MIXTURE The procedure for adjusting carburetor idle mixture can be found in the appropriate engine service manu al This procedure also requires that the ignition mod ule be locked in the Base Timing Mode IMPORTANT In order to properly set idle mixture the ignition module MUST BE locked in the Base Timing Mode This is necessary because of the Idle Speed Control feature that exists in the ignition module See information on the previous pages about this feature 1 Using a jumper wire connect the ignition system timing l
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