496 Mag HO with water in the cylinders. Help
 

at first I thought that I had a bad starter, as the engine would not roll over or budge for that matter and ruled out batteries being the prob as the other engine acts just fine. as determined there is only three possibilities of getting water in the cylinders, 1) manifold leak, 2) riser leak, 3) water entry from the lake in the exhaust pipe. I have pressure tested the manifold at 20lbs. and no leaks. I have given visual inspection to riser and will repressurize the manifold and riser tomorrow while applying heat. this is a 32' sunsation dominator with the built in swim platform. What is the likelihood of water coming up the exhaust and filling the cylinders?. it ran fine and I shut it off. I was out in the lake not at the sand bar. it wasn't all that rough. just cannot take a chance on this happening again and bending a rod.

I just chatted with AJ about this. How much water pressure are you running when on plane and at speed? At only 20 lbs. of cold water pressure, a leak may not be there; but warm at 40-45 which I have seen on 496HOs before--there could be a leak or something getting by the gaskets.

What are other 32 Dominators with 496HOs running for water pressure at speed?

Good question. I am going to have the riser and manifold die checked. If there is any way for water to get through the die will find it. there is no water infiltration ability due to any gasket failures as the water/passages do not pass/come in contact with gasketed areas. I guess after the die check confirms that there is no cracks it will have to be left to be determined as reversion and hope to hell I got real lucky with no other engine damages due to the hydrolocking. I am attempting to contact Tim Ziemer here in Lansing to complete the checks. If you have any issues or engine work needed in the Lansing, MI area I highly suggest Tim. he's very good and a great guy to work with. I will keep you posted as to what the outcome is.

Mine run at 30 - 33 pounds at speed.

Cat - Did you check to make sure your flappers are still in your tips?

flappers on the back of the boat? Yes they are there. of course they hang open at least an inch on the trailer and further when the boat is in the water due to the angle change. so the water jacket of the manifold would see 30-33 pounds correct? I believe I have saw 40 lb's at speed.

I'm assuming from your post that you have the black rubber flappers on the tips. I was referring to the steel ones up inside the tips. I'm not sure if it would be equiped with both the internal and external flaps?? look up inside your tips to see if they are all the same. I've heard the internal flaps have been known to wear out and fall out.

I see 30 - 33 on the gauges. I believe that is taken at the sea water pump.

only the externals. then the silence choice valves is it.

that might be your problem..

My 2004 Dominator had a similar issue with salt water inversion. Mercury argued the exhaust wasn't tilted/pitched aggressively enough but they approved that design years earlier. The old style Dominators sit low in the water, yours with big blocks would sit even lower than my 6.2 boat. Water can come back through the exhaust and will in the event of a wave/ abrupt stop coming off plane etc.

Looks like I am in the same boat with bad manifolds..... How did you make out????