Milky oil that smells like gas - now 4.3L swap

[jon705]

I have a 1990 OMC 4.3L cobra. Ran great last season. Winterized by the book. First time out on the water she idles fine but when throttling up she shakes and there's a knocking sound. Pulled the freeze plugs in the manifolds and nothing comes out. Shouldn't water come out? Not sure this is relevant to anything. Visible check of the engine reveals nothing no leaking fluids or signs of damage. Anyway checked the fluids and found the Ps reservoir was empty. The oil level read full but was grey. Took her home to fill the Ps reservoir and change the oil. Extracted 5+ qts of grey, gas-smelling oil. Unfortunately I think I know the answer but can anyone confirm what's going on?

 

[ENSIGN]

Re: Milky oil that smells like gas

Re: Milky oil that smells like gas

Remove the spark plugs and see if there's any water on them or in the cylinders.There should have been water in the manifolds,possibly cracked or the drain hole is clogged.

 

[jon705]

Re: Milky oil that smells like gas

Re: Milky oil that smells like gas

Remove the spark plugs and see if there's any water on them or in the cylinders.There should have been water in the manifolds,possibly cracked or the drain hole is clogged.

No water on the plugs or in the cylinders. The cyramic portion on one of the plugs cracked upon removal and not because of tweaking or wrenching on it hard. Thought maybe that could be the culprit so replaced it with a new plug and still same issue.

If the engine and outdrive are out of alignment can it cause these symptoms, or will an alignment issue only show itself when in gear? My symptoms occur both in gear and in neutral.

Anything else to check? Thanks in advance.

 

[jbetzelb]

Re: Milky oil that smells like gas

Re: Milky oil that smells like gas

A bad fuel pump could put fuel in the oil on engines of this era. Possible it is failing and not getting enough fuel pressure to the carb. Lack of fuel then causes the lean running condition. Lean condition could cause the spark plug to fail. Just something to check.

 

[jon705]

Re: Milky oil that smells like gas - now 4.3L swap

Had a couple friends come over to confirm that the block is likely cracked so guess I'm looking at replacing the engine. They also think there are hairline cracks in each of the manifolds however they are small enough that while running no water leaks through them but shows up as one or two drips. Anyway, if these manifolds are cracked can they be repaired?

Any advice for getting the motor out of the boat? I have an engine hoist but don't believe it has enough reach.

The current motor is a 1990 so when I'm looking for a swap candidate what years would be compatible? Initial research tells me to start with 1987 for the one piece rear main seal and look for nothing newer than 1992 since that's when a balance shaft was incorporated into block design. Is a post-1991 engine with balance shaft ok for my application?

 

[jon705]

Re: Milky oil that smells like gas - now 4.3L swap

A few other friends of mine have commented on my situation and think a cracked block may not be the issue. Of course they haven't heard the engine yet and are just going on description.

At one point during storage the cover came off and rain water collected in the bilge (silly me forgot to remove drain plug before storing). One person thinks water may have seeped into the oil pan through the gasket when the bilge filled. Is this even possible? His recommendation is to change the oil a couple more times to get the milky stuff out. Will this work?

Another thought I had is the 87 octane gas I'm using. Is this causing a poor running condition? It's what I used last year without issues but wanted to throw it out there.

Thanks in advance.

 

[bruceb58]

Re: Milky oil that smells like gas - now 4.3L swap

Before jumping to conclusions that the block is cracked, just pressure test the block.

I also agree with previous poster to check the fuel pump if you have gasoline in your oil. You have a mechanical fuel pump on your engine(most likely a yes)?

 

[HT32BSX115]

Re: Milky oil that smells like gas - now 4.3L swap

Yes. Instead of asking other people if they "think" the block is cracked, pressure test it and you'll know.

Anyway checked the fluids and found the Ps reservoir was empty.

Ok I'll bite........"Ps"? Power steering?

Not related to your problem but I'll say that it appears that there hasn't been a lot of careful maintenance on this engine......

If the manifolds are not getting water, the rest of the engine is probably not getting a LOT of water (because the "Ps" cooler is possibly completely plugged from a disintegrated impeller......) and it's overheating..... causing detonation on power-up.......


Gas-smelling oil is a failed fuel pump. Gray-oil is oil mixed with water.

Pressure check the block.



Good luck,


Rick

 

[jon705]

Re: Milky oil that smells like gas - now 4.3L swap

So after taking a short vacation I'm back to working on the boat. Compression tests ok, engine oil is clean after changing a few times then running on muffs as well as up and down the river. The block pressure checks ok. These lead me to believe the block is ok.

Also changed the points, condensor, cap and plugs. Set points and timing.

Ran it from a gas can using fresh 93octane gas. The virbation and noise (appears to be coming from the crank) are still there.

If I go the replacement route do I need to stick with a 1987-1991 donor motor? Use all my existing pieces except block and rotating assembly?

 

[Bondo]

Re: Milky oil that smells like gas - now 4.3L swap

So after taking a short vacation I'm back to working on the boat. Compression tests ok, engine oil is clean after changing a few times then running on muffs as well as up and down the river. The block pressure checks ok. These lead me to believe the block is ok.

Also changed the points, condensor, cap and plugs. Set points and timing.

Ran it from a gas can using fresh 93octane gas. The virbation and noise (appears to be coming from the crank) are still there.

If I go the replacement route do I need to stick with a 1987-1991 donor motor? Use all my existing pieces except block and rotating assembly?

Ayuh,.... That's Correct,.... Newer than '91 is easily adaptable if ya go that way too...

 

[jon705]

Re: Milky oil that smells like gas - now 4.3L swap

Ayuh,.... That's Correct,.... Newer than '91 is easily adaptable if ya go that way too...

My initial plan was to swap all the boat stuff - accessories, water pump, heads, intake, manifolds, starter - onto the auto block. My understanding was that with a 1987-1991 it would be fairly simple. Problem is that the available engines in that vintage are from owners and who knows what problems I'll inherit.

My local auto yard has a complete running 1992 with 30 day warranty that I would like to get. What are the adaptation issues? Can I still use the items mentioned above? From reading the forum I gather I'll need an electric fuel pump. Anything else?

 

[jon705]

Re: Milky oil that smells like gas - now 4.3L swap

Found a 91 S10 motor with just under 100k miles for $190 so the swap begins.

Started the tear down process of the original 4.3 a week and half ago. It was a treat to hoist it out of the boat but a friend and I did it with hoist at max height, air out of trailer tires, trailer nose up and me lifting the back side of the engine over the transom so that the oil pan cleared. After getting into the tear down I found a long hairline crack on the block in the lifter valley and one cracked head - so much for reusing the heads.

Tore down the donor motor and all internal parts are in good shape and within factory manual specs/tolerances. This morning finished up the accessory swap so she's ready to go back in the boat. Final steps will be to install exhaust manifold studs and recheck everything on the back of the motor - it's a real pain to work in that area while in the boat!

In case anyone finds this thread in a search here are the new gaskets needed as well as other parts that will not come with the truck motor:

Head gasket kit: NAPA FPG17211
Timing cover gasket kit: NAPA FPGTCS45121
Rear main seal kit: Autozone BS40520
Outdrive gasket set: NAPA SME182613

Crankshaft studs (6): Carquest 675-041 (7/16"-20 & 7/16"-14 at 2" total length)
Electric fuel pump: Jegs 180-P4389
Electric fuel pump relay: Jegs 555-10564
Oil pressure safety switch: Jegs 555-11200

Don't think the family and I will be on the water for the 4th holiday but maybe by this weekend which is much quicker than we anticipated.

 

[aerobat]

Re: Milky oil that smells like gas - now 4.3L swap

use new manifolds or at least very carefully pressure test the old ones ! if the old ones are leaking and you overlook it you may run into a hydrolock when on the intake side or pouring water may rust your exhaust valves and finally you will drop a valve when on the exhaust side.


both will ruin your new engine !

 

[Howard Sterndrive]

Re: Milky oil that smells like gas - now 4.3L swap

sounds like your power steering cooler might be busted up inside from ice too.

If the boat was winterized by the book, are you sure someone didn't take it out boating again after?

 

[jon705]

Re: Milky oil that smells like gas - now 4.3L swap

The power steering cooler is ok. I removed the lines during winterization.

No one took it out again. It's a mystery what happened and I've heard numerous theories

 

[Howard Sterndrive]

Re: Milky oil that smells like gas - now 4.3L swap

then either your p/s pump or actuator is leaking then - or a hose in between -because power steering fluid can't exit the inside of the hull anywhere but the cooler.

 

[aerobat]

Re: Milky oil that smells like gas - now 4.3L swap

No one took it out again. It's a mystery what happened and I've heard numerous theories

i think i went through a similar valley of pain like you did. came from outboards, new to inboards - knew that winterizing is needed and opened the drained plugs. no or very little water came out- so i closed them again and thought the job is done only to find next spring a shot manifold and a broken thermostat housing. i was very very lucky there was no damage on the block or the head ( volvo penta 3.0 ), but nevertheless i learned my lesson hard that when you open the drain plugs there MUST water come out - when not your drain is blocked - the engine has not self draining - if it really " self drains" you already have a crack or a leak.

happy boating with the new engine !