Me&wiser 470, 485, 488, 17OMR and19OMR

1 Chapter TenMe&wiser 470, 485, 488,17 OMR and 19 OMRThis chapter covers the MerCruiser 224 cid4-cylinder engine variously designated as 470, 485and 488. The 1985 470 and 488 models wereredesigned as 170MR and 190MR respectively toindicate the use of the new style gear housing. Allmodels of this engine are essentially the same,differing primarily in camshaft profile and valvetrain cylinders are numbered l-2-3-4 from frontto rear. Engine firing order is arms are retained by individual threadedbolts. A simple ball pivot valve train is used, withcamshaft motion transferred through the hydrauliclifters to the rocker arms by crankshaft is supported by 5 main No.

2 3 bearing takes the thrust. Crankshaftrotation is counterclockwise when seen from thedrive unit end of the chain-driven camshaft rotates directly in thealuminum cylinder bores and is located above thecrankshaft in the engine oil pump is located on the bottom front ofthe block on the starboard side and is driven by thedistributor (Table 1 and Table 2) andtightening torques (Table 3 and Table 4) are at theend of the SERIAL NUMBERThe engine serial number is stamped on a platemounted on the front left side of the engine blocknext to the heat exchanger (Figure 1).This information identifies the engine andindicates if there are unique parts or if internalchanges have been made during the model run.

3 It isimportant when ordering replacement parts for the serial number plate and/or model decalsare missing, check the cylinder head stamp (Figure2) and color of the valve spring to determine theengine model:a. MCM 470/170MR-stamped 0 or nostamp in cylinder head. Single coil valvesprings with an orange MCM 485-stamped 5 in cylinder springs with internal dampener havered/green or blue/white MCM 488/190MR-stamped 8 in cylinderhead. Valve spring use an external dampenerand green TOOLSW herespecialtoolsarerequired orrecommended for engine overhaul, the toolnumbers are provided. While these tools cansometimes be rented from rental dealers, thosecarrying a J prefix can be purchased fromKent-Moore, Inc.

4 , 28635 Mound Road, Warren,Michigan 48089. Tools carrying a T prefix can bepurchased from Owatonna Tools, Inc., Attn: FordOrder Desk, Owatonna, MN. 55060. Part numberswith a C prefix are from Mercury PARTSV arious changes are made to automotive engineblocks used for marine applications. NumerousMERCRUISER 470,485,488,17 OMR AND 19 OMRpart 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 insteadof the standard steel used in automotiveapplications. Brass expansion or core plugs must beused instead of the steel plugs found in ;Heat exchangerSince 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 these reasons, automotive-type parts shouldnot be substituted for marine components.

5 Inaddition,Mercuryrecommendsthat 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 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 engine is heavy, awkward to handle and hassharp edges.

6 It may shift or drop suddenly duringremoval. To prevent serious injury, alwaysobserve the following Never place any part of your body where amoving or falling engine may trap, cut or If you must push the engine during removal,use a board or similar tool to keep your handsout of Be sure the hoist is designed to lift enginesand has enough load capacity for your Be sure the hoist is securely attached to safelifting points on the engine should not be dtscult 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 Remove the engine hood cover and all panelsthat interfere with engine removal.

7 Place to oneside out of the Disconnect the negative battery cable , then thepositive battery cable . As a precaution, remove thebattery from the Disconnect the throttle cable at the necessary, remove cable from anchor Disconnect the instrument panel wiring harnessconnector plug from the harness receptacle (Figure3, typical).254 CHAPTER TEN5. Disconnect the fuel lines at the fuel pump(Figure 4). Plug the fuel lines to prevent Disconnect the brown and black (shift interlock)wires from the shift plate terminal Disconnect the red and black power trim pumpmotor wires at the Disconnect the trim indicator sender wires (if soequipped).

8 9. Disconnect the water inlet hose. Open theengine drain valve(s) and drain all water from Disconnect the exhaust elbow bellows (Figure5).11. Disconnect the drive unit shift cable from the Jclamp on the flywheel Disconnect the intake manifold vacuum hose,if so Disconnect any accessories connected to theengine that will interfere with Attach a lifting bracket to the engine liftingeyes. Connect the bracket to an engine hoist andelevate it enough to remove all 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 the front and rear engine Slide the engine forward sufficientlydisengage it from the drive shaft Remove the engine from the boat INSTALLATIONE ngine installation is the reverse of removal,plus the Coat the engine coupling splines with UniversalJoint Lubricant (part No.)

9 C-92-74058).2. It may be necessary to rotate the crankshaftslightly to align the engine coupling splines with thedrive shaft. You may also rotate the drive shaft byplacing the outdrive in forward gear and rotatingthe Install the front engine mount Position a large fiber washer on top of the innertransom plate mounting brackets (Figure 6).Position the special split lockwasher inside thefiber AND 190MR255 Steel washerATTACHMENTBtOp adjusting SCmWguideBrass barrel5. Position engine over the transom platemounting brackets. Install hose clamps over therubber exhaust elbow bellows, then fit bellows overthe exhaust manifold outlet and tighten the clampssecurely.

10 See Figure 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 Install steel washers and spacers on themounting bolts, then insert bolts down through therear engine mounts, washers and mountingbrackets. See Figure 7. Install elastic stop nut onbolts and tighten to specifications (Table 3 or Table4).7. Turn adjusting nuts in front mounting bracketuntil bracket rests solidly on the mount location inthe boat. See Figure 8. Install mount to boat:CA UTIONIf the alignment tool specified in Step 8 is notavailable, take the boat to a MerCruiser dealerfor proper alignment.