I am replacing the port engine - 7.4L Blue Water Merc's due to raw water backflush when i shut the engine off. The fix is apparently to put an additional 3" spacer so the riser's do not let this happen. Is anyone else having this problem.
I've heard this before and the fix was exactly the same. Risers are prone to rusting & clogging, needing replacement after a few years. There's a few aftermarket companies specializing in exhaust components. Possibly they are making a riser with the extension built in?
I just replaced the port engine on my 1997 330SD, also due to water ingestion. At first my mechanic thought I would need the 3" riser extensions too. Upon carefully examining the exhaust manifolds, he believes that the water ingestion was due to the manifolds going bad. I did a good amount of research, because I heard that it was a well recognized problem with my generation Searay. I found out that the "recognized" problem really started with the 1998 models, especially the 310. I was told that Merc changed the valve overlap, or some such thing, which contributed to a water ingestion problem. Good luck with your new engine.
exhaust If room and budget allows it is always recommended to add 3inch spacers. Technically your exhaust hose leaving the elbow its down angle should be greater than 13 degrees. If not. You have a chance for ingestion. Also recommended is to have exhuast that has salt water running thru it to be replaced with mercrury ceramic coated exhaust.
Tosh As a previous Sea Ray 38 owner and with a friend who is on his 6th set of engines, I am well aware of the water intrusion problem that Sea Ray has. Starting with the intake/exhaust valve overlap and ending with exhausting the engine thru the bottom into the salt water (a vacuum created which sucks salt water up thru the exhaust), their engines (Mercruiser) are prone to premature failure. They have engineered numerous fixes over the years (cannister muffler, etc.) but it still remains a huge problem for them - which they will never admit. They will blame it on environmental issues and manifolds failing, but the bottom line is that there is a design flaw in their system. You can work on the angle of the exhaust, etc. but to date there is no guaranteed solution.
