water in engine

[cadillacman]

I have a 1990 Nautique- 351pcm. I was getting water in the oil. Several "mechanics" told me cracked block. I replaced ex. manifolds first- no diff. I then put new motor in. Hooked up garden hose to the sea water pump, tried to turn over, motor completely hydrolocked. Water passing through w/o motor running, filling muffler and backwashing through the manifolds. Should this be happening? :evil:

[WakeSlayer]

RE: water in engine

Did you put the same heads and intake back on it? Define "mechanics" and "put a new motor in".

[cadillacman]

RE: water in engine

New long block. Only the intake was reused. I took the intake off and seald up the water journals and filled w/ water to see if it would hold water, and it did. I talked to 3 or 4 different marine mechanics, and they all thought the block was cracked. In the past when I ran the boat in the driveway, I dont remember any water coming out the tailpipe unless the motor was running. Now I have constant water flow w/o the boat running.

[DavidF]

RE: water in engine

I may be wrong, but that is normal for the water to flow out the exhaust with the hose running...it has to go somewhere. With the engine cold, the thermostat is closed and the water is bypassing the block and heading straight for the exhaust manifolds and out the exhaust pipes.

You said you replaced the exhaust manifolds. Did you orient the riser gasket correctly? Did you replace the risers or at least inspect them?

[bchesley]

RE: water in engine

The intake could also be cracked. That is the only piece that you have not replaced, but that is taking into account that all other items have been replaced and are functioning properly.

[WakeSlayer]

RE: water in engine

Something is goofy. i never run the hose for more than a second or two without the boat running, and would suggest the same. In fact, get someone to start the hose for you about 2 seconds before you start the motor. The impeller and water pump should restrict the water when the boat is off, but if you have a lot of water pressure it can blow by, which is not good for the water pump.

I think David is on the right track here, there are ports or gaskets that are not lined up properly.

Stupid question, but did you put a PCM RR engine back in it? or just a new longblock engine?

[maxpower220]

Any decent machine shop can check the intake and the old engine for cracks. It should not cost too much money to have that done.

It is also possible that your intake is warp and will not seal.

[cadillacman]

thanks for the reply. I'm going to try running the motor using the five gallon bucket method, letting the motor draw from a supply, rather than forcing it. I wasnt sure if a machine shop could test the intake manifold or not, so I will start making some calls. The long block was built per PCM specs.

[DavidF]

Re: RE: water in engine

The intake could also be cracked. That is the only piece that you have not replaced, but that is taking into account that all other items have been replaced and are functioning properly.

This seems like a plausible explanation and it could also be that the head to intake seal is leaking at the water jacket.

So, if it were me and I was getting water in the oil and I knew for certain that the block was not cracked (or was hoping against hope), I would pull both the intake manifold and exhaust risers. Inspect both carefully and clean them up. If not cracked, I would replace all gaskets and ensure a water tight seal on each.