Figuring out which riser gaskets to use?

willett

Cadet
Joined
May 24, 2011
Messages
23
Hey guys.
I have a carbed mecruiser 260 ( 5.7) and I have a bunch of stuff apart for upgrades and maintenence. One of the things I pulled are the exhaust elbows. The old gaskets were quite crusty and I can't tell if they were open closed or restricted. It kind of looks like they may have been closed and somebody hogged them out but I don't know for sure.

How do I determine which gaskets to replace them with and what are the benefits of having flow vs no flow through the exhaust elbows? I would think more flow = cooler and cooler is better.

I run coolant in the engine (using a heat exchanger) (I think you folks call it a closed a cooling system) and run it strictly in the summertime in freshwater in the Pacific Northwest.

Sorry about my lack of marine terminology. I'm a ticketed mechanic but I play with big dry land equipment most of the time.
 

CamaroMan

Petty Officer 1st Class
Joined
Mar 18, 2016
Messages
323
I bought and used the felpro cerramic gaskets and made my own. I assume you are referring to the steel plates? I dealt with this last month - the old ford systems had small weep holes that introduced water into the exhaust system, where the GM style apparently did not - this from other forums I visited since I wanted to pressure test my manifolds / block and elbows.

Fyi - I bought corroseal on amazon and literally filled anything touching seawater with it and let it drain out and left it for a week to dry / cure (stat housing, manifolds,elbows). Before this I left muratic acid in the manifolds to remove any surface rust, flush VERY well with water, let dry completely then do the corroseal - it worked great. Im convinced ive prolonged the life of my parts significantly as its raw water cooled :)

The surfaces are all very hard and purple glazed looking - hopefully it will combat the rusting. 1qt was about 25 bucks.
 
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