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Water In Oil, engine seized

T

tswillow

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This is the ciff notes version of what I found on my sons Merc 4.3. Not sure of the age of the boat, but guess it at 15 years

He bought the boat used last year. He used it most of the summer. It seemed doggy to me and ran a bit rough. The bilge would have water in it after a day on the lake.

This spring he ask me to get it started for him. I pulled it home, charged the battery, put on a set of ear muff cooling cups. The engine turned slowly but did start. I noticed water dripping from the bottom of the engine into the bilge. Shut it off and recommended he take it to a local boat repair shop, he did.

They replaced the starter, drained the oil (quite sludgy from the way it was explained to me) and changed the spark plugs (still the original plugs, painted in) . Found the leak,a freeze plug. Ran the engine and found water in the oil. They diagnotised the problem as exhaust manifold leaks. Replaced the manifolds and tested the engine for 3 hours at the shop. My son picked up the boat ($3,200.00 later). Put it in the lake and it ran very well...for 30 minutes then seized up.

We talked to the boat repair shop and they were at a loss to explain the reason it failed. They indicated aprox $6,000.00 it they have to replace engine. That is not going to happen, my son can't afford that. We decided to take this on ourselves (should have done the exhaust manifolds ourselves but didn't have the time to get in done for a graduation party he was planning)

Build a 12' high by 10' wide ganty crane out of 2 x 8's and a 1500 lb winch I had laying around. Pulled the engine yesterday. Have it on an engine stand in my garage. Went to drain the oil today. The first few drops were WATER. And the oil is cloudy. Obviously there is still a water leak somewhere in the system yet. So now we have a (in all likelyhood) a spun bearing and a water leak.

The reason I an writing this is to ask how do I check the cooling system for leaks? I am fairly handy around the garage (just finished a 2 year restor on a 69 Camaro) but I'm not familar with the cooling system on a marine engine.

Any suggestions would be greatly apprecaited.

Tom
 
What is wrong here is the Marine shop not you.

The last thing on a V6 to cause water in the oil (with a freeze plug blown out) is the manifolds (which were most likely cracked also)..........Any moron with any engine background would know this!!!!!!!!!!!!!

You got screwed out of $3200........

Answer here is, Motor is Junk.

The reason the freeze plug popped was because the previous owner did not winterize the motor at all.

Thus you know have a cracked block. NO REPAIR!

Look on line and do a google search for remanufactured motors or craigslist for a replacement V6 Mercruiser motor and be done with it.

Don't waist time trying to make this one work. It wont.

It is possible to get a motor for around $1500- $2000........if you do your research.
 
Ck the engine coupler for damaged/worn gear teeth. Replace now w/engine out. Examine the floor, stringers, engine mount bases and transom carefully for rot especially at the edges of any holes or cutout/openings in the transom.
 
tswillow said:
..............
The reason I an writing this is to ask how do I check the cooling system for leaks? I am fairly handy around the garage (just finished a 2 year restor on a 69 Camaro) but I'm not familar with the cooling system on a marine engine.

Any suggestions would be greatly apprecaited.

Tom
Click to expand...

Sad to say but if it blew out the expansion plug over winter Kghost is likely right. If it's a cracked block and a spun bearing, I'd just go the long block route.

Not 100% conclusive but you "could" try plugging all the coolant ports on the engine and pump 20 psi of air into the system. Listen for the air leak. If its from the crankcase you'll likely hear it from the oil fill. A head gasket from a spark plug hole.

There is some repair for cracks in cast out there. Your mileage may vary with them.
Check this one ..........................
https://youtu.be/Pq0wfU4ZaKk
 
Sealed the water system and pressurized to 40 PSI. Can hear air leak in the oil fill spout. Have the oil pan off and can hear air leaking there also. Still not sure what I'm facing (beside the spun rear main bearing we found yesterday)

IF this is the worst case (block crack) can I find a Chevy 4.3 V6 from a car or truck and after switching all manifolds, carb, starter, oil pan ect. use that? Not sure what all makes a "marine" engine other that some of the obvious bolt on components.
 
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