I bet it is water pressure. Any suggestions on what brand to use? Will I be able to use the same ones if I change to a Bravo shop 2' shortie?

I am not running external or internal flappers. Will the water make the trip up CMI tails with e-top CMI's coming off plane? Do I at least need a set of rubber flaps (external) to keep water from reverting, or is this not a concern? I am getting conflicting information on this. My engine builder states that water could never make it back up the steep pipes. So, right now I am running wide open exhausts with no mufflers.

Any other ideas? Thanks.

Most of the time it is a head gasket or intake gasket leak. The motors MUST be torn down and new bearings installed A light brown milky oil color is enough to scuff the bearings. The cm is not too large for CMI's. I dought it is coming up the pipes but flappers and stops are a god idea. Do them for yourself to eliminate that concern.

If it idles with no milk, cruises with no milk, then comes in on WOT, its more than likely a intake seal problem. Head gaskets usually do not cause any problems as long as the decks & heads are flat and torqued correctly. Where the heads milled any? When you take it apart look closely at the front of both intake to head seals. The bottom of the seal is where this happens. I use only Mr Gasket 108 or 121 seals here since they have the widest sealing surface. I had a lot of problems with Fel pro intakes at this point especially if something was changed from stock.

Good luck

The heads were done by Jim V.

You mentioned the bearings might be scuffed. If the engine builder does not put in new bearings, what will happen? I am rather new at this, so I do appreciate the help. Thanks.

Mercury wants $300/each for by pass valves. This seems a little steep, any other suggestions. Thanks.

I bought adjustable ones from McMaster-Carr for about $40 each. I will see if I can find the part info.

That sounds a lot better. Are you able to set how much water pressure you want? Did most people know to do this prior to testing motors? I can't imagine everyone going through this. Does it always result in water in the engine, or is just because of the gasket used?

I do appreciate your help.

Here is what I used, part # 9763K12 on catalog page #432.

I made a "t" that went in-line after my raw water pump and ran a line to the valve. When the pressure reached the point that I had the valve set for,which it reached very quicky, the valve would open. I had the dump go thru the transom and connet to a drive shower.

I adjusted to dump at approx 20#

I think the installation of the headers and the addition of the crossover (eliminated circulating pump) raised the pressure in the system. I also think the high pressures also cause premature failures in the circulating pumps.

Thanks for the help. This is certainly cheaper than Mercury. I can't understand the difference between $40 and $300. Either this isn't the same thing, or someone isn't giving me the actual price! I know Mercury is high, but that is ridiculous.

Thanks again.

$300 vs. how much is this going to cost you with down time, pulling the motors, going thru the motors, bearings, reassembly, reinstallation, etc. $300 seems pretty cheap. You just saved the money by not being on the water and paying for gas!

The engine builder should stand behind this since he rigged the whole thing. He has a two year warranty. But you are right about the gas savings! This project has doubled what was planned. I'm out of $.

It always does! Mine are running strong (so far) after rebuilds this spring ... So I just spent $305 and $352 in fill ups last weekend .. can't complain ... I guess?!?!?

Good luck