Leaky Exhaust Manifold on 4.3L Merc?

[rylleeryllee]

I have a 4.3L Merc inboard. I had a crack in my intake manifold and I have replaced it. When I start the engine, it seems to experience hydrolock (sounds like it's sporatically undergoing load). It runs rough and steam starts to come out of the valve cover vent on the starboard side of the boat. I have taken out all the plugs and turned over the motor. It turns over perfectly even with the earmuffs connected with the water turned on. When I put the plugs back in and turn it over with the coil wire disconnected, after it turns over 2-3 times, it seems to experience hydrolock. There is no water getting into the engine, the oil is still clear. The compression is 120 psi in each cylinder and no water in the cylinders. I'm wondering if it could be the gasket on the exhaust manifold on the one side? Any other suggestions?

 

[jtybt]

Re: Leaky Exhaust Manifold on 4.3L Merc?

Did any water come out the plug holes when you turned it over? Were the plugs wet with water? Did you fool with the timing or plug wires.

You're not telling everything you did...or didn't do.

 

[rylleeryllee]

Re: Leaky Exhaust Manifold on 4.3L Merc?

I took out the plugs and turned it over. No water came out and the plugs were not wet. I checked three times. I verified that the plug wires are all in the correct order. I didn't fool with the timing.

 

[rylleeryllee]

Re: Leaky Exhaust Manifold on 4.3L Merc?

Here is the background. I started up the boat in the spring and it started up fine. I put it in the water and boated for about 5-10 minutes and then it stalled. I opened up the hood and saw that there was milky oil coming out of the valve cover vents. I took the boat out of the water, drained the milky oil, ran new oil through it twice and then replaced the oil and the oil filter. I took the boat into a boat shop and they removed the intake manifold, saw a crack underneath and replaced it. They could not see any cracks in the block or heads. The boat shop indicated that there is a pocket in the manifold that water can remain in if the boat is sitting at a certain level. I started the boat and that's when I noticed it running rough and steam coming out of the one valve cover vent. The boat ran perfectly before it stalled in the water.

 

[Bondo]

Re: Leaky Exhaust Manifold on 4.3L Merc?

it seems to experience hydrolock (sounds like it's sporatically undergoing load). I have taken out all the plugs and turned over the motor. It turns over perfectly even with the earmuffs connected with the water turned on. When I put the plugs back in and turn it over with the coil wire disconnected, after it turns over 2-3 times, it seems to experience hydrolock. There is no water getting into the engine, I took out the plugs and turned it over. No water came out and the plugs were not wet.

Ayuh,... It's Not Hydro-lock if there's No Water in the Cylinders...

You have a Different Problem...
Starter or flywheel maybe...

 

[rylleeryllee]

Re: Leaky Exhaust Manifold on 4.3L Merc?

i tried the boat on the lake today. it ran fine at low speeds but when I tried to speed up, it was like there was no power. It was if it was being held back. I have no idea.