Help water in my oil

[motorboatin123]

I think my motor is done:facepalm::facepalm:..
1989 thompson twin merc 470 4 cylindars. Finally got the steering cable fixed and the starter. Now the real problems start
Took the boat out for the first long run of the season. After about 30 min of crusing one of my motors started to run hot. (same motor that will not get above 3k rpm after changing cap,rotor, plugs, wires, filters and cleaning out carb). It wasnt "overheating" but it was running on the hot side. Didnt hit the REDLINE so I didnt stop the boat. After about an hour and a half of crusing I stopped and everything was fine. I checked the oil everything seemed good. About 3 hours later I started the trip home and I figured I would check the anti freeze just to make sure its full and not the cause of it running hot. IT WAS EMPTY! I filled it with water and headed home. About 30 min into the trip(with the motor still running on the hot side) the motor shut off. When I looked there was a milky mix of water and oil actually shooting out of the dipstick. I drove home on one motor and that was that. Next day I go to the boat and sure enough if starts right up no problem. I shut it right off cause of all the water in the oil(halfway up the dipstick) but now what? cracked block? Head gasket? Cam seal(but i had one go and it leaked water out of the waterpump not into motor)??? I dont even know where to start. compression test?

 

[stonyloam]

Re: Help water in my oil

compression test?

Yes. And clean out that antifreeze contaminated oil.

 

[motorboatin123]

Re: Help water in my oil

That's it? That's easy enough but that will tell me if it's the head gasket correct?

 

[stonyloam]

Re: Help water in my oil

Correct. On a 470 there are not too many ways for water to get in the oil. Cam seals probably not, cracked block unlikely in an antifreeze filled block, cracked head maybe, blown head gasket, best bet, especially with the loss of power and overheating and a pressurized crankcase in that engine. Look for some cylinders to be around 140 or so and some very low

 

[motorboatin123]

Re: Help water in my oil

results of the compression test is
cyl 1 115
cyl 2 110
cyl 3 90
cyl 4 80
head gasket or cracked head im assuming correct?
was the impeller bad causing it to run hot causing the head gasket to go bad

 

[motorboatin123]

Re: Help water in my oil

HELP can I use a head gasket for a ford 460 since its the same head?

 

[stonyloam]

Re: Help water in my oil

I would guess a blown head gasket between 3 & 4, but they are all a little low. Time to pull the head. Make sure to keep the pushrods and rockers in the correct order. Best bet is to use an OEM Mercruiser head gasket. Grab this manual: http://www.4shared.com/document/zTbCbkDD/Service_Manual_08.html Couple of other things, take a look at the spark plugs, if white and clean, coolant is probably getting in the cylinders. Will need a valve job, I had hardned exhaust seats put in mine, and ask the machinest to measure the valve height so that when you put it back in the pushrods will be right. Bad impeller as cause, very likely.

 

[Doernuth]

Re: Help water in my oil

Based on your compression readings, even the high ones and based on the fact that the engine is an '89 it might be time for an overhaul. Pull the head and inspect the pistons and determine if a rebuild is in order.

 

[guyaverage]

Re: Help water in my oil

^^ What he said.

twin merc 470 4 cylinders

My sympathy.....I feel bad enough with one 470 to deal with.

You are putting an iron head onto an aluminum block, dont use just any old 460 head gasket. It will physically fit, and will work short term, but the material is likely different. Be safe and use a genuine Mercruiser head gasket, its not expensive, around $45 or so. Dont go cheap on this part. Also make sure you check the deck and head for flatness.

As Stony pointed out, get that antifreeze/oil mix out of there as much as possible, as quickly as possible, and find out why this overheated before you start it up and run it again. Its possible the head gasket was the cause and the victim in this case, but a few hours of investigation will avoid future repeat headaches.

I'm all for the overhaul suggestion, but its not my money I'm spending by saying that. If you really like this boat, now would be the time.

 

[motorboatin123]

Re: Help water in my oil

ok that was a big job for nothing!!! Put the new head gasket on. started up ran great for the first 20 min then it started to run hot and of course the water is a quart or so low and now the oil has water it in again. Now what? What else can it be. no cracks anywhere in the head, valves look good cylindars wall no cracks..

 

[Doernuth]

Re: Help water in my oil

You may need to check the block for warpage.

I think it may be time to pull the engine and have it checked out by a machinist.

Sorry about your luck....

 

[motorboatin123]

Re: Help water in my oil

I spoke to a boat mechanic today. He mentioned that the head could be warped? I can take the head to a machine shop but I am not sure I want to keep spending time and money on this motor.