rust on top of cylinders 488 merc io

[spareparts]

riser gasket, or the riser itself. replace both(use teh merc riser gasket) if you rebuild the engine. Check hte manifold as well. There is not an automotive head gasket available for that engine as its a mercruiser engine, never used in a car.

[richardk5457]

Originally Posted by spareparts

riser gasket, or the riser itself. replace both(use teh merc riser gasket) if you rebuild the engine. Check hte manifold as well. There is not an automotive head gasket available for that engine as its a mercruiser engine, never used in a car.

thank you for the info, mon. will take a hard look at riser and manifold, will probably buy new ones, for it is difficult to establish the inner wall condition of both parts unless you can advise on propper way to check both, would be glad to attempt this before ordering. again thank you for the time and suggestions. richard

[spareparts]

flip the riser over and look inside the exhaust passage, poke around with a screw driver and see if it pokes thru the inner wall. The manifold is a little tougher, first inspect the gasket surface where the riser meets. Secondly, pull the manifold, block off the hose fittings with some spare hose. level the manifold on a table, fill the water jacket till it almost comes thru at the riser flange, let it sit over night and see if the level drops. If you want to, you can make a block off plate and pressure test the manifold

[cfelton]

Id follow Spares advice! It sounds like a bad riser or leaking gasket. Check Mercruiser Parts Express, thats where I got mine from. Its an original replacement.

[step up here]

look into buying a used motor . there are some good running motors available now at days. you will need more parts then you think once you start on this project. good luck! Break Out Another Thousand spells boat.