One of the members suggested running the motor with the water discharge removed from the tail. Did you try that? Pull the manifolds off completely and run it. Put cardboard facing the exhaust and look for water. I have a 24 Scarab concept with a blown 489 that I built. Had the same problem and I was running stock exhaust ( was only temporary). I made extensions ( about 10 inches long ) and attached them to the riser, better but still had water issues. Went to dry exhaust and problem solved. My cam is a hyd 576 lift with a 114. I feel you pain.......................

How would a bad oil cooler put water in the exhaust ???

i was wondering that also,i have had issues with the eddie exhaust manifolds ,the revert quite easily.i dont like them for this reason.

i am sure someone has mentioned this but have you checked the angle of the thru hull exit? is there enough of a downward slope from the riser out to the transom? if it is even level it could cause the water to run backwards when shutting engineoff.

x 2.

I've even seen some revert simply because of running a boat on a trailer with the nose of the trailer down too far.

Even ran into a confused person who hydrolocked their motor because of this. He thought something exhaust or engine related, I saw trailer hooked to truck and truck nose down the driveway, asked if that was how boat was started, and he asked yeh, why, and then I explained.

So...at minimum, with boat on trailer start it only as boat sits in water....better yet....get the nose of the trailer and thus nose of boat as high as possible.

Although there are some other reasons, a decent reason that I don't like - along with Gill's and some others - is the smooth transition from inner dry pipe to outer wet pipe. Water is mixed here too with the exhaust of course. Too smooth and easy for water to come back up. What I'd like to see is a more abrupt change. Say a 3.5" inner pipe with no flanging to the outer, or dare I say, 3" inner pipe. LOL. That would keep more distance from where the water mixes to the actual outlet of the dry inner pipe.

That is the reason we took off the Gil's and installed the Stainless Marine and never looked back.

I also installed Stainless Marine.(dry)

So here is an update on my reversion issue. what i ended up doing is I went to 16 inch stainless risers which eliminated the silent choice. I then added 3/4 inch water dumps off of each manifold which goes through the transom. I installed silicone exhaust hoses and put a piece of 4 inch stainless tubing inside the exhaust hose from the riser to the exhaust tip for added security against burn through since im not running as much water through the exhaust riser and into the exhaust stream. next was the drew marine exhaust tips that were fitted with GGB 5.5 inch inserts. I also installed a ball valve to bypass all water going to the exhaust system and it dumps out the transom so i can dry the manifolds and pipes out if needed. This actually works awesome because these manifolds sweat inside if they dont get warmed up hot enough and i can tell you they dont sitting on a trailer flushing the motor. So when its time to flush the motor after a day on the salt at the end of my flush i bring the rpm's up to about 1800 close the ball valve water then is bypassed over the side count down 25 seconds bring the motor down to idle and shut her down. I have been doing this for 2 seasons and it is a proven method, I pull the exhaust manifolds off in the fall for inspection of the manifolds and risers as well as the exhaust valves and seat areas and all are in great condition. This boat was ran in fresh water before i bought it and I believe these engines do ok with a little reversion in fresh water they can tolerate it better but when introduced to salt its whole new program which i run in salt. Salt can and is very hard on things. Its my understanding that the the 454 and 502 mag motors do ok when the exhaust is routed through the prop and the factory water shutters are in good shape which happen to be a very good one way positive seal but when you add the silent choice to the system you have created a leak it may be a small one but it is a leak and the motor has a place to pull from at that point. I hope this will help any other boaters out there.

Thanks for the update. Wow, kind of amazing that you had to go through all that trouble for a stock mag engine running the stock cam. I always thought it was pretty safe to run those cams without much worry for reversion. I had a lot of reversion issues with my 489 running a fairly conservative cam on a 114* LSA, and I was running Lightnings with it. I'm kind of to the point where the idea of going back to stock power is appealing - would rather keep the hatch down and worry about running out of beer instead of my engine blowing up.