VelocityMike

My aunt has a 29 Scarab with twin Merc 350 Small Blocks. At the start of the season both engines were missing extremely bad so she took it in for repairs and they found two cylinders on each engine pooched because of water, both engines had 250 hrs on them. The reason for the water we were told was there were no flappers in the exhaust and so water was getting back in the exhaust thus into the engine. Two long blocks later she was boating again until they winterized the boat and found rust on the plugs again. Now her friend is saying cam overlap. Does anyone know if this is a problem on this motor? Any advice would be great.

29scarab

The small blocks from mercruiser were suppose to be built to hinder water reversion back into the cylinders. I have not heard of too many issues on cam problems. The flappers could have been a problem. Also their have been issues with the exhaust gaskets leaking at the flange where it seperates the manifold and the pipe on top of the manifold.

I personally have had problems with that. There have even been problems with the exhaust having internal cracks on the jacketed header. A mechanic ought to be able to pressure test the exhuast manifolds and check for leaks. I would start their first.

Good luck!

redfountain420s

I also own a 30ft scarab with twin small blocks and had the same problem with mine when i bought it and it was the exhaust that was the problem. I had the manifolds and risors resurfaced and that solved the problem. But my boat has gil high tourqe exhaust not stock. Its been 4 years since i had the problem