Re: 88 5.8L OMC
Before you decide on replacing the engine, make some checks: credit others:
Water in Engine
Important Information
IMPORTANT: First determine location of water in engine. This information can be of great help when trying to determine where the water came from and how it got into the engine. The three most common problems are "water on top of pistons, water in crankcase oil, water in crankcase oil and on top of pistons."
The first step, after locating water, is to remove all the water from the engine by removing all spark plugs and pumping cylinders out by cranking engine over. Next change oil and filter. Now, start engine and see if problem can be duplicated. If problem can be duplicated, there more than likely is a mechanical problem. If the problem cannot be duplicated, the problem is either an operator error or a problem that exists only under certain environmental conditions. If water is contained to cylinder(s) only, it is usually entering through the intake system, exhaust system, or head gasket.
If the water is contained to crankcase only, it is usually caused by a cracked or porous block, a flooded bilge, or condensation.
If the water is located in both the cylinder(s) and the crankcase, it is usually caused by water in the cylinders getting past the rings and valves, or complete submersion.
Checking for rust in the intake manifold or exhaust manifolds is a good idea. Rust in these areas will give clues if the water entered these areas.
Water In Crankcase
1. Water in boat bilge
Boat has been submerged or bilge water was
high enough to run in through dipstick tube
2. Water seeping past piston ring or valves
Refer to "Water in Engine" ("On Top of Pistons")
3. Engine running cold
Defective thermostat, missing thermostat;
prolonged idling in cold water
4. Intake manifold leaking near a water passage
Loose or cracked intake
Bad intake gasket
Corroded head or intake
5. Cracked or porous casting
Check cylinder head, cylinder block, cylinder walls,
and intake manifold
6. Valve cover cap or breather missing, ( only gets water when it rains)
Water On Top Pistons
1. Operator shut engine off at high RPM (at or above planning speed)
2. Engine "diesels" or tries to run backwards
Engine out of tune, poor fuel, high idle RPM,
timing set too high, intake leak
3. Rain water running into flame arrestor
Hatch cover leaking or left open
4. Spark plug misfiring
Improper combustion causes moisture in the
air to accumulate in the cylinder
5. Backwash through the exhaust system
6. Improper engine or exhaust hose installation
(water coming back up exhaust)
Boat overloaded or filled with water
7. Cracked exhaust manifold
8. Improper manifold to elbow gasket installation
9. Loose cylinder head bolts
10. Blown cylinder head gasket
Check for warped cylinder head or cylinder block
11. Cracked Valve seat ( drawing water from exhaust when running)
12. Porous or cracked casting
Check cylinder heads, cylinder block, and intake manifold
