exhaust mans / risers

[sunburnt]

how can i tell when exhaust@ risers are bad just aquierd 87 boat 305 gm looks real clean has been sitting for 4 yrs fresh h20 only white smoke /steam ? plugs normal good compression 165 to 170 all 8 cyl no blowbuy no smoke on start up like vavle seals bad my first i/o ibelive there is a pressure test what does sho w leaks between exhaust @ water discharge is it possible to suck water into cyl

 

[bjcsc]

Re: exhaust mans / risers

Holy moly... throw us a bone...a punctuation mark here and there, one or two complete sentences mixed in for sport. It's hard for people to give you an answer when they have to struggle to read your post.

That said, you take them apart and check the joint sealing surfaces. A little steam running at home is normal, a pressure check could give you a "false positive". Yes it can suck water back into the cylinders. It's right up there with freezing in leading causes of engine death...

 

[Don S]

Re: exhaust mans / risers

What engine and drive? Mercruiser, OMC, Volvo? ? ? they all used 305's.
The best way to check manifolds and risers is to pull the risers, inspect and replace the gaskets.
My first thought about your steam when started is a bad raw water pump impeller. After sitting for 4 years, it's probably dead and not pumping enough water to keep the exhaust cool.

 

[sunburnt]

Re: exhaust mans / risers

thanks ! i will pull the risers just to confirm. could you plz explain how water can be seht to the cyl,s . my guess is thru the gaskets or thru rotted mans or risers . by the way it is an omc 1987 305 cu. in. cobra 504 pary. scary tryihg to compress water .the raw pump was replaced ahd the t- stat also.

 

[bjcsc]

Re: exhaust mans / risers

There are lots of ways it can get in, but the way it gets in when the gasket fails and/or manifold/riser integrity fails, is simply by gravity. The water leaking past the gasket, or through the failed wall of the manifold or riser, goes to the lowest point, right to the exhaust ports. When the exhaust valve opens, the water goes in. Do you suspect you have manifold/riser problems? Or do you have water getting into your cylinders and you're trying to find out why? A little steam is normal running on a hose as the flow is much less than running in the water and the exhaust is hot...you said spark plugs look normal - I assume that means they are not super clean (i.e. steam cleaned) or rusty?

 

[sunburnt]

Re: exhaust mans / risers

good afternoon bjcsc. not a sign of water on plugs or elsewhere .i was curious as to the white stuff. smoke or steam; more like steam.i will pull risers and check what you mentioned . tx