Help with 91' Four Winns 4.3L OMC - water in the oil

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Jul 2, 2008
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Ok, I'm at witts end here, i bought a 1991 Four Winns 195 Freedom last spring from a local hero Soldier. he was deployed and didnt have boat winterized. so I knew going in, i'd have to fix, or replace the motor. I was told that I could use any pre vortec 4.3L longblock. upon inspection, the orig. block was crack thru the valley and the heads were pretty much just boat anchors. So I just opted for a new motor, and got a rebuilt 4.3L and ensured it had a New marine cam. Put it all together, got it running smooth, took it to the lake, After an awesome 10min boat ride up the river, the boat pops, does a nose dive... and their we are, dead in the water... after about a 6 hour wait for help. we get it back to the dock, on tailer, and home. Found out the upper unit was toast. being new to boating, wasn't too keen on oil levels in the upper and lower unit. and given the condition of the gears, the previous owner didn't either. Spend 2k having that rebuilt, and learning how to properly check the fuild in the outter unit Thus, headed back to the lake. 2nd trip out on the water, after a nice 10min boat ride just slowly cruisin about, still trying to just get a "feel" of her, she just dies. after checking the normal few things, found the positive cable a lil loose, and upon tighenting it, the clamp broke, thus being stuck out on the water yet again... Go back, and opt for new battery, clamps and cable, just for good JP. 3rd trip, we went out, it stayed running for more than 10 min, so we thought, "Hey! all the bugs work out, we're good to go" so we travel up river bout 10 miles or so to a cove, kill the engine, drop anchor, and just kickback and have fun floating with friends. after sitting for a few min, i opt'd to start the boat up, just for whatever reason, i can't remember now. but it wouldn't start. it sounded, like it was out if time, which i knew it wasn't. I'm assuming now it hydrolocked. after about 30mins or so, we got it started headed back to the dock and then home. got to looking, and found the oil was just like a wendys frosty. and i had about 4 gallons it. upon draining, it darn near filled a 5 gallon bucket up. figured it was maybe a bad head gasket or manifold gasket, put a new set of those on,changed the oil and filter. hooked up the hose and let it run for 10 min, and checked the oil , and the same thing, its full of water. I said okay, we pulled the heads again, and really looked over the heads and intake. I knew the heads and block were magnafluxed and checked prior to assembly. and its never got cold enough to doing any damage since we started working on this. following the correct procedures, reinstalled the heads, and intake. got it all back together. run it for 10mins or so, and Bam!, same problem. I asked around and learned that it maybe the exhaust manifolds, because one of them had welds on the bottom of it, where it had been repaired, so I spent 600.00 for another set of exhaust manifolds off of Ebay, put those on, changed, drained the oil. fired it up and let it run and same thing happened again. Is there something I'm overlooking here? Ive search thru this forum, and I found just a statement relating to this sort of thing about plugging a water port but I'm not sure where this would be, when using a car motor in a boat. I'm wondering now if thats what I need to do, or is there something else I'm doing wrong. Any help is appreciated, as my checkbook and pateince is fairly low now trying to solve this on my own.
 

danond

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Re: Help with 91' Four Winns 4.3L OMC - water in the oil

Did you use your old intake manifold on the new motor? Might be cracked...
 
Joined
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Re: Help with 91' Four Winns 4.3L OMC - water in the oil

yes I did use the old intake, but theres no signs of any freeze damage to it, theres only one water passage on it and its in the front of intake, by the Tstat housing.
 

fishmen111

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Re: Help with 91' Four Winns 4.3L OMC - water in the oil

You said you replaced the manifolds...did you also replace the risers?
 

Bondo

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Re: Help with 91' Four Winns 4.3L OMC - water in the oil

Ayuh,....

I'd suspect he Intake Manifold 1st,....
And,..
The Exhaust Manifolds 2nd....
 
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Re: Help with 91' Four Winns 4.3L OMC - water in the oil

Im new to boating and not sure if I have risers. the exhaust manifolds are one piece, they go from head to a rubber boot and metal coupling, to another rubber boot into a another metal coupling with flaps in it. from there it goes into transom, and out thru prop.
 

Boatin Bob

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Re: Help with 91' Four Winns 4.3L OMC - water in the oil

You should have risers, see flow diagram below



91cooling.jpg
 

danond

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Re: Help with 91' Four Winns 4.3L OMC - water in the oil

Do your manifolds look like this?

OMC984222.jpg
 
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Re: Help with 91' Four Winns 4.3L OMC - water in the oil

yes the manifolds look exactly like what danond has posted
 

danond

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Re: Help with 91' Four Winns 4.3L OMC - water in the oil

Then you don't have risers! If your manifolds are leaking into the cylinders, it's time for new manifolds. You can get after-market replacements on eBay for $800.
 
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Re: Help with 91' Four Winns 4.3L OMC - water in the oil

i dont mean too sound smart, but I never said I did Boatin Bob said I should have em, and I knew I didn't, and i've already replaced the exhaust manifolds.
 

thumpar

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Re: Help with 91' Four Winns 4.3L OMC - water in the oil

Go back to post #5.
 

Boatin Bob

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Re: Help with 91' Four Winns 4.3L OMC - water in the oil

Sorry...didn't mean to mislead you but the manual and the parts catalog both show that motor having risers.
 
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Re: Help with 91' Four Winns 4.3L OMC - water in the oil

ok... can you post pic from manual that points them out? Thanks for your help...
 

CharlieB

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Re: Help with 91' Four Winns 4.3L OMC - water in the oil

You said
I was told that I could use any pre vortec 4.3L longblock.

Not necessarily true.

Pull your intake and inspect both the manifold and the gaskets, you'll see your answer.
 
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Re: Help with 91' Four Winns 4.3L OMC - water in the oil

ok... I will look again sunday morning, but we have already replaced the gaskets and head gaskets twice, and didnt see anything before. can you give any details to look out for?
 

CharlieB

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Re: Help with 91' Four Winns 4.3L OMC - water in the oil

You are looking for the slightest trace of a discoloration of the manifold gasket and/or manifold contact area, indications of water or rust that would show the presence of water.

You just mentioned that you have already replaced the head gaskets?

Is this a marine engine or an automotive long block?

4.3 marine applications should NOT reuse headbolts, especially the torque/turn installed bolts, they have been installed at their prescribed bolt stretch and annealed by repeated heat cycling during use. Reused headbolts can allow headgasket leakage at WOT in a marine application, it may be fine in a car, not for a boat.

Replace head gaskets AND head bolts.

While the heads are off recheck surfaces to ensure that they have not been warped due to inadequte head bolt tension when ran under full load.
 
Last edited:

CharlieB

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Re: Help with 91' Four Winns 4.3L OMC - water in the oil

Re-read your original post, found

"got a rebuilt 4.3L and ensured it had a New marine cam"

Does this engine have a 'marine' water pump and 'brass' soft plugs in it?

These things WILL come back to haunt you later.

Automotive engines generally will not last a year in a marine application. Even the pistons are not suitable for sustained full load operation.
 
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Re: Help with 91' Four Winns 4.3L OMC - water in the oil

yes Im using a marine water pump and it has the brass plugs.... is there a difference in the automotive head and head gaskets and marine?
 

danond

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Re: Help with 91' Four Winns 4.3L OMC - water in the oil

Sounds like you need to do a pressure test of the block before you start taking things apart again.

You can pressurize the engine by connecting the two manifold water lines together, disconnect the hose that goes to the transom (comes in on the left side of the thermostat housing as you face the front of the engine) and hook up a compressor or a bike pump, whatever you have, to the intake port on the thermostat housing. Drain the block and cooling system, pressurize it with about 15 psi of air and listen for the air leaking somewhere.

Lastly, you should really get an OMC manual for your drive and engine combo.
 
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