GM V6 And VS Engines - West Virginia University

Chapter SevenGM V6 and VS EnginesA wide range of GM powerplants has beenoffered for MerCruiser installations. Enginesinclude the 229 cid V6, the small block VS indisplacements up to 350 cid, and the large block V8(or Mark IV) up to 482 cid.The Chevrolet-built V6 and V8 engines are verysimilar in design and construction; there is littledifference in the repair and service procedures forthese engines. The procedures given in this chapterare typical and apply to all engines, except wherespecifically noted.The V6 engine cylinders are numbered fromfront to rear: l-3-5 on the port bank and 2-4-6 onthe starboard bank. The cylinder firing order isl-6-5-4-3-2. The V8 engine cylinders are numberedfrom front to rear: l-3-5-7 on the port bank and2-4-6-8 on the starboard bank. The cylinder firingorder is l-8-4-3-6-5-7-2.Hydraulic valve lifters and pushrods operate therocker arms and valves. No lash adjustment isnecessary in service or during assembly unlesssome component in the valve train has beenreplaced.The cast iron crankshaft is supported by 4 (V6)or 5 (V8) main bearings. Crankshaft rotation iscounterclockwise when seen from the drive unitend of the engine.The chain-driven camshaft is supported by 4(V-6) or 5 (V-8) bearings and is located above thecrankshaft between the 2 cylinder banks. The oilpump is located on the bottom front of the blockand is driven by the distributor.Specifications (Tables 1-4) and tighteningtorques (Table 5) are at the end of the chapter.ENGINESERIALNUMBERThe engine serial number is stamped on a Flatemounted at the rear of the engine on the flywheelhousing (Figure 1).This information identifies the engine andindicates if there are unique parts or if internalchanges have been made during the model run. It isimportant when ordering replacement parts for theengine.SPECIAL TOOLSWherespecial tools are required orrecommended for engine overhaul, the toolnumbers are provided. Mercury Marine tool partnumbers have a “C” prefix. GM tool part numbershave a “J” prefix. While GM tools can sometimesbe rented from rental dealers, they can bepurchased from Kent-Moore, Inc., 28635 MoundRoad, Warren, MI 48089.REPLACEMENTPARTSVarious changes are made to automotive engineblocks used for marine applications. Numerouspart changes are required due to operation in freshand salt water. For example, the cylinder headgasket must be corrosion-resistant. Marine enginesuse head gaskets of copper or stainless steel instead

GM V6 AND V8 ENGINESof the standard steel used in automotiveapplications. Brass expansion or core plugs must beused instead of the steel plugs found in automotiveblocks.Since marine engines are run at or nearmaximum rpm most of the time, the use of specialvalve lifters, springs, pistons, bearings, camshaftsand other heavy-duty moving components isnecessary for maximum life and performance.141For these reasons, automotive-type parts shouldnot be substituted for marine components. Inaddition, Mercury recommendsthat onlyQuicksilver parts be used. Parts offered by othermanufacturers may look alike, but may not bemanufactured to Mercury’s specifications. Anydamage resulting from the use of other thanQuicksilver parts is not covered by the MercuryMarine warranty.REMOVALSome service procedures can be performed withthe engine in the boat; others require removal. Theboat design and service procedure to be performedwill determine whether the engine must beremoved. In some installations, it may benecessary to remove the stern drive unit first. SeeChapter Fourteen.Serial numberWARNINGThe engine is heavy, awkward to handle and hassharp edges. It may shift or drop suddenly duringremoval. To prevent serious injury, alwaysobserve the following precautions.1. Never place any part of your body where amoving or falling engine may trap, cut or crushyou.2. If you must push the engine during removal,use a board or similar tool to keep your handsout of danger.3. Be sure the hoist is designed to lift enginesand has enough load capacity for your engine.4. Be sure the hoist is securely attached to safelifting points on the engine.5 . The engine should not be dtficult to lift with aproper hoist. If it is, stop lifting, lower the engineback onto its mounts and make sure the enginehas been completely separated from the boat.1. Remove the engine hood cover and all panelsthat interfere with engine removal. Place to oneside out of the way.2. Disconnect the negative battery cable, then thepositive battery cable. As a precaution, remove thebattery from the boat.3. Disconnect the throttle cable at the carburetor(A, Figure 2, typical). If necessary, remove cablefrom anchor plate (B, Figure 2, typical).4. Disconnect the engine-to-dash wiring harness.5. Disconnect the fuel lines at the fuel pump. Plugthe fuel lines to prevent leakage.6. Disconnect the shift cables from the shift plate(Figure 3, typical), then remove the cables from theJ-clamp on the exhaust manifold (Figure 4).

142CHAPTER SEVEN7. Disconnect the water inlet hose.8. Disconnect the exhaust elbow bellows.9. Disconnect the reverse lock switch wires fromthe trim pump. Disconnect the trim pump wires(red and black) from the engine or battery.10. Remove the gray “down” hose from thereverse lock. Remove the black plastic hose fromthe trim sender. Plug hoses and cap connections.11. Open the engine drain valve(s) and drain allwater from the block.12. Attach a lifting bracket to the engine liftingeyes. Connect the bracket to an engine hoist andelevate it enough to remove all slack.NOTEAt this point, there should be no hoses, wires orlinkage connecting the engine to the boat orstern drive unit. Recheck this to make surenothing will hamper engine removal.13. Remove the bell housing-to-engine bolts.14. Remove the engine mount-to-deck mountbolts.15. If clearance is limited, remove the enginemounting brackets.16. Slide the engine forward sufficiently todisengage it from the drive-shaft assembly.17. Remove the engine from the boat with thehoist.ENGINE INSTALLATIONEngine installation is the reverse of removal,plus the following.1. Fit a double-wound lockwasher and a fiberwasher on top of each inner transom plate enginesupport. See Figure 5.2. Lower engine in place over transom plate andconnect exhaust bellows to elbows while lowering.Let rear engine mounts rest on transom plateengine supports but do not remove hoist tension.CA UTIONElastic stop nuts should never be used more thantwice. It is a good idea to replace such nuts withnew ones each time they are removed. Never useworn-out stop nuts or non-locking nuts.3. Install one steel washer and spacer on each rearmount bolt. Install bolts downward through enginemounts, washers and brackets. Thread elastic stopnuts on bolts and tighten to specifications (Table4).4. Use guide bolts to align the engine to the bellhousing. It may be necessary to rotate thecrankshaft slightly to align the engine couplingsplines with the drive shaft. You may also rotatethe drive shaft by placing the outdrive in forwardgear and rotating the propeller.5. Coat the engine coupling splines withmulti-purpose lubricant.CA UTIONIf the alignment tool specijied in Step 6 is notavailable, take the boat to a MerCruiser dealerfor proper alignment. Drive shaft/coupling splinemisalignment can cause serious damage.6. Coat the solid end of alignment tool part No.C-91-57797A3 with multipurpose lubricant andinsert it from outside the boat through the U-jointbellows into the gimbal bearing. Index the bearingand drive shaft with the engine coupling splines. Ifindexing is difficult, raise or lower the engine withthe hoist as required to permit indexing with noresistance.7. Tighten all fasteners to specifications (Table 4).Remove the alignment tool.8. Close all water drain valves.9. Fill the engine with an oil recommended inChapter Four.10. Fill the cooling system, if equipped with aclosed system. See Chapter Twelve.11. Adjust the drive belts. See Chapter Thirteen.DISASSEMBLYCHECKLISTSTo use the checklists, remove and inspect eachpart in the order mentioned. To reassemble, go

143GM V6 AND VS ENGINES05TRANSOM PLATEWASHER INSTALLATIONDouble wound-3-lthrough the checklists backwards, installing theparts in order. Each major part is covered under itsown heading in this chapter, unless otherwisenoted.Decarbonizing or Valve Service1. Remove the rocker arm cover.2. Remove the intake and exhaust manifolds.3. Remove the rocker arm.4. Remove the cylinder head.5. Remove and inspect the valves. Inspect valveguides and seats, repairing or replacing as required.6. Assemble by reversing Steps 1-5.Valve and Ring Service1. Perform Decarbonizing or Valve Service.2. Remove the oil pan.3. Remove the pistons with the connecting rods.4. Remove the piston rings. It is not necessary toseparate the pistons from the connecting rodsunless a piston, connecting rod or piston pin needsrepair or replacement.5. Assemble by reversing Steps l-4.General Overhaul1. Remove the engine from the boat.2. Remove the flywheel.3. Remove the engine mount brackets and oilpressure sending unit from the engine.4. If available, mount the engine on an enginestand. These can be rented from equipment rentaldealers. The stand is not absolutely necessary, butit will make the job much easier.5. Check the engine for signs of coolant or oilleaks.6. Clean the outside of the engine.7. Remove the distributor. See Chapter Thirteen.8. Remove all hoses and tubes connected to theengine.9. Remove the fuel pump. See Chapter Eleven.10. Remove the intake and exhaust manifolds.11. Remove the thermostat. See Chapter Twelve.12. Remove the rocker arm assemblies.13. Remove the crankshaft pulley/vibration ‘, *# 1,damper and timing case cover. Remove the timing : ’ : ” :chain and sprockets or the timing gears.14. Remove the camshaft.15. Remove the seawater pump, if so equipped.See Chapter Twelve.16. Remove the cylinder heads.17. Remove the oil pan and oil pump.18. Remove the pistons and connecting rods.19. Remove the crankshaft.20. Inspect the cylinder block.2 1. Assemble by reversing Steps l- 19.ROCKER ARM COVERRemoval/Installation1. Remove the carburetor vent hose from thestarboard cover.2. Disconnect the spark plug cables at the plugsand remove the plug cable retainers from theirbrackets on the cover.3. Remove the cover attaching screws.4. Tap the rocker arm cover with a plastic malletto break the gasket seal. Remove the rocker armcover.5. Clean any gasket residue from the cylinder headand rocker arm cover with degreaser and a puttyknife.6. Coat one side of a new gasket with anoil-resistant sealer and install sealer-side down onthe cylinder head.7. Install the cover on the cylinder head.8. Install the attaching screws and tighten tospecifications (Table 4).9. Install the spark plug cable retainers on therocker arm cover brackets. Connect the wires to theappropriate spark plugs.10. Install the carburetor vent hose in the rockerarm cover.