bob53magnum

Has anybody experienced water intrusion into a Merc 502 Gen 6,
415HP EFI engine with Stainless Marine Manifolds and Risers? Thanks

bigredbaja

yes it happend to me turned out i had a cracked water jacket on my IMCO exhaust manifold, how old is the exhaust system?

bob53magnum

It appears to be about 15 years old. Jerry at stainless and everybody else I have talked to says they have never experienced a failure with these manifolds. I thought it would be in the riser, but cannot find a leak with hot water.

bigredbaja

I would pull them and have them pressure tested mine were about the same age i purchased them used and ran across a less than honest guy they were bad when he sold them to me and he knew it! Cost me about $5k by the time it was all done, I had the boat to a well respected mechanic, he and everyone else kept thinking head gasket or reversion and finally after the second engine milk shake a small shop near my home lake pulled the exhaust manifolds and tested them. So another $700 for new stock manifolds & risers and the problem was solved.

Blueabyss

If you have thru hull exhaust and your internal flappers are burned out, it may be coming from there. External flappers are not 100% effective. You really need both.

Chris

liquidlounge

iTrader: (1)

you definitely have reversion with any motor that has an over lapping valve events. T he key is minimizing its effects. The S/m manifold with the short riser is no better and probably a little worse (as would most aftermarket manifolds w/ the short stainless riser) than the factory manifolds. The overlap in a stock 502 mag should be pretty minimal though. Do you idle for long periods of time thru no wake zones etc? Try to keep the revs up a little more and/or rev the motor up in neutral from time to time... if water reversion is actually the problem.

bob53magnum

Thanks for the reply. I still have not found the "smoking gun" and HOPE it is just reversion. I tested the manifold and sent the riser to SM for testing. I will try and pressurize the block and heads this weekend. If evverything tests good, I will put everything back together and start it up and see what happens.