Mercruiser 888 302 Ford exhaust elbow question...

[MT1]

I was given a very clean boat from a family friend and decided to change the heat exhaust rubber bellows today. Its a Ford 302 Mercruiser 888 and for the most part in really good shape for its year. After cutting off the rubber bellows I saw I needed to take off the exhaust elbow to service the bellows. I un bolted the elbow and grabbed the back of it to pull it off the exhaust manifold. That is when I felt things werent as in as good of shape as they looked. LOL So I pry off the crumbling elbow and start looking it over. The question is are the ports for the water jacket going into the elbow from the exhaust supposed to be seperated by a solid stainless steel plate between the gaskets? In looking it over I have fresh green antifreeze at the ports of the exhaust but nothing is getting to the elbow that has the matching ports because of the plate that seperates it. The gaskets have the matching holes as the ports its just a piece os s/s sheet metal sanwhiched in between the gasket that prevents the fluid from flowing through. Something says this isnt right and maybe the reason for the falure of the elbows? They are ultra dry and crumbling. Im a Hot Rod Builder by trade and as if you couldnt tell new to this boat thing. Any help or direction would be appreciated.

 

[MT1]

Ok in looking things over I think I might have figured it out... I think that is where the anti freeze and lake or ocean water is kept seperated. In looking it over I see whats going on... If it didnt have the antifreeze system the stainless plate would be removed and allow the lake water to circulate through out the whole system. But being we have two diffrent cooling systems that is where they are kept seperated? That might account as to why the exhaust manifold looks in such good shape and the elbow is trash... salt water?

 

[Bt Doctur]

You are correct about the block off plate. A "full system" cools the manifolds also and the riser need to be isolated from the A/F and just accept the waste water from the heat exchanger. typical life of elbows/riser is around 5-6 years.

 

[MT1]

You are correct about the block off plate. A "full system" cools the manifolds also and the riser need to be isolated from the A/F and just accept the waste water from the heat exchanger. typical life of elbows/riser is around 5-6 years.

So if I wanted to build a stainless steel elbow there really isn't any need to bolt it to the top of the exhaust manifold? I cant believe it would be cooling anything with that amount of contact area especially being blocked off? It seems like I could cap off the top of the exhaust manifold and fab up a 3" stainless U bend tube to dump the dirty water down and out one end,cap off the other end and install a hose fitting for the inlet water on the oppisite end? I don't want to do this every 5 years and everything else looks to be in good shape... Am I thinking right or does that elbow do something else? I think the stock elbow would be necessary if it was using the lake water for all it's cooling?

 

[haulnazz15]

So if I wanted to build a stainless steel elbow there really isn't any need to bolt it to the top of the exhaust manifold? I cant believe it would be cooling anything with that amount of contact area especially being blocked off? It seems like I could cap off the top of the exhaust manifold and fab up a 3" stainless U bend tube to dump the dirty water down and out one end,cap off the other end and install a hose fitting for the inlet water on the oppisite end? I don't want to do this every 5 years and everything else looks to be in good shape... Am I thinking right or does that elbow do something else? I think the stock elbow would be necessary if it was using the lake water for all it's cooling?

You aren't seeing what all the elbow DOES. The elbow keeps the exhaust and cooling water separate until the exit of the elbow into the y-pipe. Otherwise you'd potentially be sending water back into the exhaust stream too early which could result in reversion (sucking water back into the combustion chamber = bad). Also, you may not think that little bit of a water jacket around the elbow does much, but I doubt you'd put your bare hand on any part of your car's exhaust system after it's been running for a few minutes, it'd burn you in an instant. You can generally hold your hand on the outside of the exhaust manifold/elbow without instantly searing your skin, all because of that fresh flow of water keeping the temps in check. The rubber bellows you were speaking of wouldn't last too long without the cooled area, either.

 

[Bt Doctur]

Not yours but its how most are setup

 

[MT1]

Thanks guys for the help... Guess I will suck it up and do it every 5 years...