CORROSION PROTECTION
Contents
1. a MerCathode assembly b Screw 2 c Flat washer 2 d Lockwasher 2 90 863160030 NOVEMBER 2003 Page 6 17 19 CORROSION PROTECTION ALL MODELS SERVICE MANUAL NUMBER 28 SUPPLEMENT 6 Gently remove the MerCathode assembly and wires from the gimbal housing AG VILLLLLLL LLL LLL LALL a 24 K 70771 a MerCathode assembly wires b MerCathode assembly Installing Gimbal Mounted MerCathode System 1 The gimbal mounted MerCathode assembly has a factory installed rubber seal and does not require an O ring 79928 a MerCathode assembly b Anode c Reference electrode d Rubber seal Page 6 18 90 863160030 NOVEMBER 2003 SERVICE MANUAL NUMBER 28 SUPPLEMENT CORROSION PROTECTION ALL MODELS 2 Form a 61 cm 2 ft long piece of 0 8 mm 0 032 in diameter wire to the dimensions specified 74106 a 61 cm 2 ft of approximately 0 8 mm 0 032 in diameter wire b 12 3 cm 5 in c 45 degree angle d 13 mm 1 2 in 3 Insert 45 degree angle end of wire through center hole in hydraulic connector block 4 Guide wire through hole until wire protrudes through cavity at the bottom of exhaust pipe sr RED frame HANIS 22235 a Wire 90 863160030 NOVEMBER 2003 Page 6 19 l CORROSION PROTECTION ALL MODELS SERVICE MANUAL NUMBER 28 SUPPLEMENT 5 Secure ring terminals to guide wire 6 Guide leads through center hole in connector block IMP2. Galvanic Isolator 05 Corrosion Protection Testing and Troubleshooting 000ee een aeee Continuity Test Test Equipment Set Up Low Readings 00e0 eee High Reading 0 0 eee eee 90 863160030 NOVEMBER 2003 Normal Reading But Corrosion Is Evident 0 ccc cece eee Corrosion On The Entire Sterndrive GE eau eae ee ae re Corrosion Problem Developed After Refinishing The Sterndrive Unit Paint Blistering On Sterndrive Unit Trim Cylinder Corroding Only One Or Two Components Corroding Corrosion In The Exhaust Outlet DEG Corrosion Occurs After The Unit Is Removed From The Water Corrosion Between Surfaces Aluminum Corroding In Lubricated reas bees eoeed seed eageeeaean Stainless Steel Components Corroding Stainless Steel Propeller Corroding Paint Blistering The Metal Under The Blistered Paint Is Not Pitted Page 6 1 CORROSION PROTECTION ALL MODELS SERVICE MANUAL NUMBER 28 SUPPLEMENT Torque Specifications NOTE Securely tighten all fasteners not listed below im ibn ot moapae Jay fo MerCathode assembly mounting screws 28 S Lubricants Sealants Adhesives Where used Propeller shaft Senses an electrical current in the water when testing the MerCathode System Use to EE check hull potential Page 6 2 90 863160030 NOVEMBER 2003 SERVICE MANUAL NUMBER 28 SUP
3. battery ground d BROWN lead from reference electrode on transom assembly 90 863160030 NOVEMBER 2003 Page 6 15 1 CORROSION PROTECTION ALL MODELS SERVICE MANUAL NUMBER 28 SUPPLEMENT Removing Gimbal Mounted MerCathode Assembly Page 6 16 The Hull Potential Test should be performed to ensure that the system is functioning properly Refer to Corrosion Protection Testing and Troubleshooting following in this section 1 Disconnect the battery leads from the battery to the MerCathode controller ORN 74251 7 Standard controller shown a Lead to anode of MerCathode assembly ORANGE b Lead to reference electrode of MerCathode assembly BROWN c Lead to the positive terminal of the battery RED PURPLE d Lead to the negative terminal of the battery BLACK 2 Disconnect MerCathode assembly harness connector 79133 a MerCathode assembly b Harness connector 90 863160030 NOVEMBER 2003 SERVICE MANUAL NUMBER 28 SUPPLEMENT CORROSION PROTECTION ALL MODELS 3 Remove the wire retainer from the connector by prying out on the locking tabs and pulling the wire retainer away from the connector 4 Remove the wire leads from the connector by gently pulling them from the back of the connector 79926 79927 a Wire lead retainer b Connector c Locking tab d Wire lead 5 Remove the two mounting screws and washers holding the MerCathode assembly to the gimbal housing m TT 70771
4. system inoperable Do not power wash the MerCathode or damage to the MerCathode system will occur Page 6 28 90 863160030 NOVEMBER 2003 SERVICE MANUAL NUMBER 28 SUPPLEMENT CORROSION PROTECTION ALL MODELS Continuity Test 1 Connect the end of the positive meter lead to each metallic component on the sterndrive Ensure that there is good electrical contact to each metal surface Reading should drop below 2 millivolts 2 Areading higher than 2 millivolts indicates improper grounding If the reading is not within specified limits or if reading is within specifications but there is evidence of corrosion on sterndrive unit refer to the following troubleshooting charts to aid in diagnosis 76868 Gimbal mounted MerCathode on bottom of transom assembly a Reference wire b Anode plate 71895 Transom mounted MerCathode on boat transom a Anode b Reference electrode c MerCathode 90 863160030 NOVEMBER 2003 Page 6 29 a CORROSION PROTECTION ALL MODELS SERVICE MANUAL NUMBER 28 SUPPLEMENT Test Equipment Set Up I TITT ES i fr aa PN SE 70755 a 15 cm 6 in maximum b Power package ground c Battery d Waterline Page 6 30 90 863160030 NOVEMBER 2003 SERVICE MANUAL NUMBER 28 SUPPLEMENT CORROSION PROTECTION ALL MODELS Low Readings Cause Special instructions Loss of continuity between sterndrive Ensure that continuity devices are not unit components and negative missing or dama
5. 3 Page 6 11 13 CORROSION PROTECTION ALL MODELS SERVICE MANUAL NUMBER 28 SUPPLEMENT 4 Reinstall plug in drive shaft housing Bravo Two Sterndrive Units 1 2 Page 6 12 22093 a Rubber plug or plastic cap Loosen screw and remove anodic plate Install anodic plate screw and continuity washer Torque screw 50323 a Screw b Anodic plate Anodic plate screw 04 30 90 863160030 NOVEMBER 2003 SERVICE MANUAL NUMBER 28 SUPPLEMENT CORROSION PROTECTION ALL MODELS Bravo Three Sterndrive Units 1 Remove plastic cap to gain access to the first anode attaching screw 2 Remove the second anode attaching screw located on the under side of the prop shaft housing 76832 79285 a Plastic cap removed b First anode attaching screw c Second anode attaching screw d Under side of prop shaft housing 3 Install new anode and continuity washer Torque screw Anodic plate screw 44 30 4 Reinstall plastic cap 90 863160030 NOVEMBER 2003 Page 6 13 I CORROSION PROTECTION ALL MODELS SERVICE MANUAL NUMBER 28 SUPPLEMENT Page 6 14 Propshaft Anode Bravo Three Only kits are available for other drives is located behind the propeller 5 Install the propeller shaft anode over the propeller shaft nut 6 Place the flat washer onto the propeller shaft anode screw 7 Place the star washer onto the propeller shaft anode screw NOTE If the propeller shaft anode is remo
6. 30 NOVEMBER 2003 Page 6 23 L CORROSION PROTECTION ALL MODELS SERVICE MANUAL NUMBER 28 SUPPLEMENT Galvanic Isolator Boats that are connected to AC shore power require additional protection to prevent destructive low voltage galvanic currents from passing through the shore power ground wire Quicksilver Isolator 888557Q01 can be installed to block the passage of these currents while still providing a path to ground for dangerous fault shock currents If AC shore power is not isolated from boat ground the MerCathode system and sacrificial anodes may be unable to handle the increased galvanic corrosion potential The Quicksilver Galvanic Isolator is a solid state device that is series connected in line with the boat s safety grounding lead ahead of all grounding connections on the boat This device functions as a filter blocking the flow of destructive low voltage galvanic DC currents but still maintaining the integrity of the safety grounding circuit If the galvanic isolator kit is improperly installed false audio and visual warnings will result a Display g To distribution panel b Galvanic Isolator monitor h Circuit breaker c GREEN i Power conductors d Galvanic Isolator j Boat shore power connection e GREEN BLACK k Safety grounding conductor f Boat ground I 110 VAG power cord Page 6 24 90 863160030 NOVEMBER 2003 SERVICE MANUAL NUMBER 28 SUPPLEMENT CORROSION PROTECTION ALL MOD
7. CORROSION PROTECTION MC Transom Assys and Hydraulic Systems 0606 Corrosion Protection Information on drive unit transom assembly corrosion protection is presented in this section The pages are copied from the Bravo Drive Unit Service Manual 428 Supplement P N 90 863160030 Nov 2003 Section 7A The service manual section page numbering has been changed to match the page numbering in this manual This section covers the continuity circuit anodes MerCathode System Galvanic Isolator and corrosion protection testing and troubleshooting 2 SECTION 6 CORROSION PROTECTION SERVICE MANUAL NUMBER 28 SUPPLEMENT CORROSION PROTECTION ALL MODELS CORROSION PROTECTION Section 6 Corrosion Protection All Models Table of Contents Torque Specifications Lubricants Sealants Adhesives Special Tools aanunnumnunnnunne General Information Continuity Circuit 4 Trim Cylinder Anodes Anodic Plate 200000neeeeenees Bravo One Sterndrive Units Bravo Two Sterndrive Units Bravo Three Sterndrive Units Integral MerCathode System Removing Gimbal Mounted MerCathode Assembly Installing Gimbal Mounted MerCathode System Connect to MerCathode Controller Assembly 00 cee wees Wiring Diagrams 000eee eae MerCathode Controller Quick Connect Models
8. ELS 79773 Boat shore power connection Circuit breaker Power conductor See Note Galvanic Isolator Boat ground To distribution panel O gD Q 0 AO NOTE Green conductor cannot be connected to boat in this section 90 863160030 NOVEMBER 2003 Page 6 25 1 CORROSION PROTECTION ALL MODELS SERVICE MANUAL NUMBER 28 SUPPLEMENT Corrosion Protection Testing and Troubleshooting Page 6 26 NOTE The following corrosion protection test supersedes all previously issued tests This test can be used on applications with or without a MerCathode system This test should be performed on all boats annually where the boat is moored to ensure that the system is functioning properly Test requires the use of MerCathode Reference Electrode and a digital multi meter IMPORTANT A standard analog meter cannot be used as an inaccurate reading will result The MerCathode Reference Electrode Tester is equipped with a special connector containing a resistor to provide the proper scale reading when used with a digital multimeter Do not remove this plug or use analog meters Resistor jack can be left in place when using digital meters 76834 Digital Multi meter and MerCathode Reference Tester a DMT 2000A Tachometer Multi meter b Reference Electrode Reference Electrode Senses an electrical current in the water when testing the MerCathode System Use to check hull p
9. ION ALL MODELS Trim Cylinder Anodes Do not paint new trim cylinder anodes as this will render them ineffective as a galvanic corrosion inhibitor 1 Remove screws that secure anodes to trim cylinders 2 Remove anodes 71966 a Screws b Trim cylinder anodes 3 Clean thread holes with a 10 32 standard tap 4 Install new anodes and tighten securely 90 863160030 NOVEMBER 2003 Page 6 9 1 CORROSION PROTECTION ALL MODELS SERVICE MANUAL NUMBER 28 SUPPLEMENT Anodic Plate Do not paint new anodic plate as this will render it ineffective as a galvanic corrosion inhibitor a Anodic plate location b Anodic plate c Threaded boss up Bravo One Sterndrive Units 1 Remove plug from drive shaft housing to gain access to attaching screw 22093 a Rubber plug or plastic cap Page 6 10 90 863160030 NOVEMBER 2003 SERVICE MANUAL NUMBER 28 SUPPLEMENT CORROSION PROTECTION ALL MODELS 2 Loosen screw and remove anodic plate 76800 a Anodic plate b Screw c Socket and extension Without proper contact with the gear housing the anodic plate will not function properly Avoid corrosion to the gear housing and damage to the drive ensure that the anodic plate is installed properly 3 Install anodic plate screw and continuity washer Torque screw 76800 a Anodic plate b Screw c Socket and extension Anodic plate screw Eee 90 863160030 NOVEMBER 200
10. ORTANT ORANGE lead is approximately 15 cm 6 in longer than the BROWN lead 7 Pull leads into the boat nd TA DA 7 7777777 TITTET ENN SES UT 22234 a Guide wire b Leads Do not paint sacrificial anodes or MerCathode System anode reference electrode assembly as this will render them ineffective as galvanic corrosion inhibitors 8 Position and secure MerCathode assembly to gimbal housing using two 35 mm 1 3 8 in long screws flat washers and lockwashers 9 Torque screws Do not overtighten A SENN NNGS 7 Hj 70771 a MerCathode assembly b Screw 2 c Flat washer 2 d Lockwasher 2 e Hydraulic connector block Description MerCathode assembly mounting screws 2 8 aan Se NG Page 6 20 90 863160030 NOVEMBER 2003 SERVICE MANUAL NUMBER 28 SUPPLEMENT CORROSION PROTECTION ALL MODELS Connect to MerCathode Controller Assembly NOTE If BLACK ground wire is not available at terminal block or from wire harness install a separate lead between controller negative terminal and negative battery cable attaching point on engine 1 Securely connect electrical leads to MerCathode controller assembly Refer to Wiring Diagrams 74251 Standard controller shown a Lead to anode of MerCathode assembly ORANGE b Lead to reference electrode of MerCathode assembly BROWN c Lead to the positive terminal
11. PLEMENT CORROSION PROTECTION ALL MODELS DMT 2000A Tachometer Multi meter Kit Measures rpm on both 2 and 4 cycle marine engines records the maximums and minimums simultaneously and will read accurately in high RFI environments Replacement components 91 854010 1 Inductive Pick Up 8 ft 2 4 m 91 854011 1 Temperature Probe 91 854012 Ferrite Core 91 854013 1 Interface 91 854009A3 Module 91 854014 1 Hard Carrying A umATEMP COM vida Case 91 854015 1 User s Guide 91 802651 Test Leads Optional Accessories 84 854016T 8 ft 2 4 m Inductive Pick Up Extension 91 802650 1 Clamp On Current Probe 91 89045 1 Direct Voltage Adapter 2 you may use a digital multi meter do not use a standard analog meter as inaccurate readings will result NOTE Quicksilver VolOhm Multi meter DVA Tester 91 99750A1 is no longer recommended for testing corrosion protection 90 863160030 NOVEMBER 2003 Page 6 3 i CORROSION PROTECTION ALL MODELS SERVICE MANUAL NUMBER 28 SUPPLEMENT General Information Page 6 4 78283 Standard Bravo sterndrive unit c Sacrificial trim cylinder anode d Sacrificial anode anodic plate e Steering lever ground wire f Ground wire between gimbal ring and bell housing g Stainless steel hoses h Ground wire between gimbal ring and gimbal housing i Ground wire between gimbal housing and trim cylinder The following maintena
12. as follows e Freshwater Areas 750 1050 millivolts Saltwater Areas 850 1050 millivolts If the reading is low replace the controller Faulty MerCathode Controller Additional corrosion protection required Boats equipped with a sizable amount of underwater metal stainless steel propeller after planes etc or that are moored in an area with warm or rapid flowing water may require additional protection Install additional anodes or MerCathode system 88334A2 If the unit is already equipped with a MerCathode System a second system may be required Page 6 32 90 863160030 NOVEMBER 2003 SERVICE MANUAL NUMBER 28 SUPPLEMENT CORROSION PROTECTION ALL MODELS High Reading Cause Special instructions Stray current corrosion If an electrical current flowing along a metal conductor leaves the metal for a water path it will cause ionization of the metal and an area of rapid corrosion Observe the reading while disconnecting the electrical components one at a time until you eliminate the high reading Correct the course of stray current Poor connection between MerCathode i reference electrode lead BROWN and Clean and or tighten connection Repair R terminal on controller wiring as required Disconnect the reference electrode lead BROWN from R terminal on the controller Connect the lead to the positive terminal of a digital multi meter set on 0 2000 millivolt scale Connect the n
13. egative meter lead to the negative battery terminal Note the meter reading then repeat the test using MerCathode Reference Electrode Tester 7667511 Both tools should produce the same reading If not replace the reference electrode Faulty MerCathode controller Replace the controller Normal Reading But Corrosion is Evident CORROSION ON THE ENTIRE STERNDRIVE UNIT Cause Special instructions Leave the sterndrive unit in the IN DOWN position when the boat is moored to ensure the trim tab is in the water providing protection CORROSION PROBLEM DEVELOPED AFTER REFINISHING THE STERNDRIVE UNIT Use only a nylon or bristle brush Faulty MerCathode reference electrode The sterndrive unit Is raised so that the sacrificial anodic trim tab is out of the water A steel wire brush was used to clean the aluminum casting Steel particles became entrapped and set up a small galvanic cell PAINT BLISTERING ON STERNDRIVE UNIT Special instructions Battery charger using 110 volt shore power improperly connected to the battery Ensure the charger is connected correctly 90 863160030 NOVEMBER 2003 Page 6 33 J5 CORROSION PROTECTION ALL MODELS SERVICE MANUAL NUMBER 28 SUPPLEMENT TRIM CYLINDER CORRODING Cause Special instructions Continuity lost between trim cylinder and Install proper continuity devices sterndrive unit ONLY ONE OR TWO COMPONENTS CORRODING Cause Special Instructions Con
14. ffectively 8 Inspect the following ground circuit components at intervals for loose connections or broken or fraying wires EE SIN ZOO L Cont SY STR BAND es Fa pet REE LAR ed N IE a Steering lever ground wire 90 863160030 NOVEMBER 2003 Page 6 5 l CORROSION PROTECTION ALL MODELS SERVICE MANUAL NUMBER 28 SUPPLEMENT 22650 77079 a Inner transom plate to gimbal housing ground wire b Drive shaft housing to gear housing ground plate inside anode cavity Nr LAA KI SOC OO IOS KK 77100 a Gimbal housing to gimbal ring ground wire b Gimbal housing to trim cylinder ground wires Page 6 6 90 863160030 NOVEMBER 2003 SERVICE MANUAL NUMBER 28 SUPPLEMENT CORROSION PROTECTION ALL MODELS 22028 50242 Gasoline models Diesel models a Flywheel housing grounding stud b Ground wire c Inner transom plate grounding screw 22755 22031 a Gimbal ring to bell housing ground wire b Sterndrive unit to bell housing ground plate 90 863160030 NOVEMBER 2003 Page 6 7 CORROSION PROTECTION ALL MODELS SERVICE MANUAL NUMBER 28 SUPPLEMENT 70575 a Drive shaft housing anodic plate b Continuity washers between fasteners and hydraulic manifold block to gimbal housing 50383 22079 a U joint bellows ground clip b Exhaust bellows ground clips Page 6 8 90 863160030 NOVEMBER 2003 SERVICE MANUAL NUMBER 28 SUPPLEMENT CORROSION PROTECT
15. ged and that battery terminal connections are clean and tight Shore power green safety grounding Disconnect shore power and verify if lead not isolated from the power reading increases If so install a package ground on boats equipped with Quicksilver Isolator 888557Q01 or an shore power isolation transformer Underwater metal parts on the sterndrive unit and or boat are unpainted or the paint is in poor condition The boat has more exposed metal than the anodes and or MerCathode System can protect Anodes Anodes painted Remove paint or Remove paint or replace anodes anodes The anodes are ll EE grounded or ii anode mounting surface or inactive replace anodes if they have oxidized Anodes consumed no longer protect Replace anodes if eroded 50 or more Avoid any electrical interconnection between the Mercury MerCruiser Sterndrive unit and or boat bottom product anodic blocks or MerCathode painted with anti fouling paint containing system and the paint by allowing a tin minimum of 40 mm 1 1 2 in of UNPAINTED area around these items on the transom of the boat MerCathode reference electrode or Remove paint anode painted a heads used instead of plastic Reinstall the plastic caps Connect the positive volt meter lead set on 0 20 volt scale the positive controller terminal and the negative volt meter lead to the negative No power to MerCathode controller terminal The meter should ind
16. icate battery voltage Check for a blown fuse Prime and paint underwater metal parts This will reduce the load on the anodes and or MerCathode System if equipped on the starboard MerCathode system Clean the connection or repair wiring as required Poor connection between reference electrode lead BROWN or anode lead Clean and or tighten the connection ORANGE and MerCathode controller Repair the wiring 90 863160030 NOVEMBER 2003 Page 6 31 Id CORROSION PROTECTION ALL MODELS SERVICE MANUAL NUMBER 28 SUPPLEMENT Low Readings continued Cause Special instructions Disconnect the reference electrode lead brown from the controller R terminal Connect the lead to the positive terminal of a digital multimeter set on 0 2000 millivolt scale Connect the negative meter lead to the negative battery terminal Note the meter reading then repeat the test using a MerCathode Reference Electrode Tester 7667511 You should obtain the same reading in both cases If not replace the reference electrode Faulty MerCathode reference electrode With anode and reference electrode leads connected to the controller connect the jumper wire between R and negative terminals on the controller Connect the positive lead of the volt meter set on 0 20 scale to terminal A on the controller Connect the negative meter lead to the negative controller terminal Reading should be
17. nce items are recommended to ensure that your sterndrive unit stays corrosion free Maintain a complete paint covering on the sterndrive unit Check the finish regularly prime and paint nicks and scratches using Mercury enamel paint and touch up paint Use only tin based anti fouling paint or equivalent on or near aluminum surfaces below the waterline If bare metal is showing apply 2 coats of paint Mercury Phantom Black 92 802878 1 90 863160030 NOVEMBER 2003 SERVICE MANUAL NUMBER 28 SUPPLEMENT CORROSION PROTECTION ALL MODELS e Spray all electrical connections with sealant Liquid Neoprene All electrical connections 92 25711 3 e Inspect the sacrificial trim tab or anode plate if equipped at regular intervals and replace it before it is half gone If a stainless steel propeller is installed additional anodes or a MerCathode System will be required e Inspect the propeller shaft for fishing line which can cause corrosion on stainless steel shaft e Remove propeller at least every 60 days and lubricate the propeller shaft e Do not use lubricants containing graphite on or near aluminum in saltwater e Do not paint trim tabs or the mounting surface Continuity Circuit The transom assembly and sterndrive unit are equipped with ground circuit wires to ensure good electrical continuity between engine transom assembly and sterndrive components Good continuity is essential for the anode and MerCathode System to function most e
18. of the battery RED PURPLE d Lead to the negative terminal of the battery BLACK Apply a thin coat of sealant to all electrical connections Part number Liquid Neoprene All electrical connections 92 25711 3 Install the BROWN wire lead from the MerCathode assembly harness into connector terminal A by firmly pushing it into the back of the connector until completely seated Install the ORANGE wire lead from the MerCathode assembly harness into connector terminal B by firmly pushing it into the back of the connector until completely seated 79927 79926 a Connector b Connector terminal A c Connector terminal B d ORANGE wire lead e BROWN wire lead 90 863160030 NOVEMBER 2003 Page 6 21 L CORROSION PROTECTION ALL MODELS SERVICE MANUAL NUMBER 28 SUPPLEMENT 5 Install the wire lead retainer onto the MerCathode assembly harness wires and push it onto the connector until the locking tabs are fully engaged 79926 79925 a wire lead retainer b Connector c Wire lead 6 Connect the MerCathode assembly harness connector 79133 a MerCathode assembly b Harness connector Page 6 22 90 863160030 NOVEMBER 2003 SERVICE MANUAL NUMBER 28 SUPPLEMENT CORROSION PROTECTION ALL MODELS Wiring Diagrams MerCathode Controller Quick Connect Models 79133 a MerCathode controller b 20 Amp fuse c MerCathode assembly d Female terminal e Male terminal 90 8631600
19. or sacrificial anodes to polarize the surrounding water Be careful not to rock the boat excessively while boarding to perform a test as this will alter the test reading 90 863160030 NOVEMBER 2003 Page 6 27 id CORROSION PROTECTION ALL MODELS SERVICE MANUAL NUMBER 28 SUPPLEMENT 1 Set meter on scale required to read 0 2000 millivolts 2 Connect the negative meter lead to the negative battery terminal or other convenient engine ground 3 Connect Reference Electrode Tester lead into positive receptacle of meter 4 Immerse Electrode Tester in the water within 15 cm 6 in of aft end of sterndrive unit IMPORTANT There will be different voltage readings depending on the type of MerCathode system you are testing 5 The following readings indicate the corrosion protection status of the sterndrive unit Refer to Section 1C Troubleshooting of the appropriate Mercury MerCruiser Service Manual Digital Multi meter Corrosion protection Between 750 1050 i Sterndrive is protected millivolts Below 750 millivolts Sterndrive is corroding Above 1050 millivolts Sterndrive is overprotected Digital Multi meter Corrosion protection Between 850 1100 i Salt Polluted or Mineral ne Sterndrive is protected J millivolts Laden Water Below 850 millivolts Sterndrive is corroding Above 1100 millivolts Sterndrive is overprotected Removing the Silver Silver Chloride coating from the reference wire will make the MerCathode
20. otential 91 7667511 90 863160030 NOVEMBER 2003 SERVICE MANUAL NUMBER 28 SUPPLEMENT CORROSION PROTECTION ALL MODELS DMT 2000A Tachometer Multi Meter Kit Measures rpm on both 2 and 4 cycle marine engines records the maximums and minimums simultaneously and will read accurately in high RFI environments Replacement components 91 854010 1 Inductive Pick Up 8 ft 2 4 m 91 854011 1 Temperature Probe 91 854012 Ferrite Core 91 854013 1 Interface 91 854009A3 Module 91 854014 1 Hard Carrying Case 91 854015 1 User s Guide 91 802651 Test Leads Optional Accessories 84 854016T 8 ft 2 4 m Inductive Pick Up Extension 91 802650 1 Clamp On Current Probe 91 89045 1 Direct Voltage Adapter IMPORTANT If equipped with MerCathode System ensure that battery is fully charged 12 6 volts or above IMPORTANT Boats recently placed in service usually will produce a reading higher than normal because the sterndrive unit is protected by a good finish and new sacrificial anodes To obtain an accurate diagnosis the test should be performed after the boat has been in service at least one or two weeks This will give the paint a chance to soak and minor abrasions and scratches will have appeared resulting in a more accurate reading IMPORTANT Boats should be moored without being operated for at least 8 hours before performing tests This is necessary to allow the MerCathode system and
21. sion Burying stainless steel in sand or silt can also cause this problem Remove foreign matter and prevent surfaces from being covered by sand or silt STAINLESS STEEL PROPELLER CORRODING Cause Special instructions Clean the mating surfaces on the propeller propeller shaft and attaching parts If applicable install a continuity washer Lubricate the propeller shaft before reinstalling the propeller Special Lubricant 101 2 4 C with Teflon Anti Corrosion Grease Propa orana Perfect Seal PAINT BLISTERING THE METAL UNDER THE BLISTERED PAINT IS NOT PITTED Cause Special Instructions Sand the surface down to bare metal prime and repaint with Quicksilver Spray Paint Continuity lost between propeller and propeller shaft The surface was not properly prepared before paint was applied 90 863160030 NOVEMBER 2003 Page 6 35
22. tinuity lost between sterndrive unit If not already done install Continuity and components Circuit Kit 99940A2 CORROSION IN THE EXHAUST OUTLET AREA Cause Special instructions Exhaust gas deposits accumulating on the sterndrive exterior can result in paint blistering and corrosion Remove deposits with marine or automotive wax CORROSION OCCURS AFTER THE UNIT IS REMOVED FROM THE WATER Cause Special instructions Salt crystals remaining on the surface of the sterndrive components combine with Wash sterndrive exterior and flush high humidity to cause electrolyte sterndrive interior with fresh water formation resulting in corrosion CORROSION BETWEEN SURFACES Salt buildup between surfaces Protect mating parts with lubricant 2 4 C with Teflon Propeller shaft 92 342271 ALUMINUM CORRODING IN LUBRICATED AREAS Cause Special instructions Never use lubricants containing graphite Graphite in the lubricant because they accelerate corrosion Use specially formulated marine lubricants 2 4 C with Teflon Propeller shaft 92 342271 Page 6 34 90 863160030 NOVEMBER 2003 SERVICE MANUAL NUMBER 28 SUPPLEMENT CORROSION PROTECTION ALL MODELS STAINLESS STEEL COMPONENTS CORRODING Special instructions Foreign matter fishing line marine growth etc covering the steel and starving it of oxygen This causes a breakdown of the protective oxide film and subsequent corrosion known as oxygen starvation corro
23. ved after initial installation and is to be reinstalled it will be necessary to apply Loctite Thread Locker 271 to the threads of the propeller shaft anode screw 8 Secure the propeller shaft anode to the propeller shaft using the propeller shaft anode screw and washers Torque the screw Description an a Propeller shaft anode screw 0 3125 18 x 1 5 in 88 mm 97 o J long a Propshaft anode 90 863160030 NOVEMBER 2003 SERVICE MANUAL NUMBER 28 SUPPLEMENT CORROSION PROTECTION ALL MODELS Integral MerCathode System The MerCathode system automatically protects the drive unit from corrosion The increased output provides greater protection for underwater aluminum parts Its reliable efficient operation requires an insignificant amount of current when protection is needed The blue MerCathode controller output is limited to approximately 200 mA to avoid rapid drain of the boat s battery MERGATHODE 79094 Single MerCathode application In saltwater a second MerCathode system blue controller may be added in parallel to increase protection to 400 mA Please note that this will also increase the drain on your battery Refer to the Mercury Precision Parts Marine Corrosion Protection Guide 90 881813003 MERGATHODE MERGATHODE 79095 Dual MerCathode application a ORANGE lead from anode on transom assembly b RED PURPLE lead connect to positive battery terminal c BLACK lead from engine harness or
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