I currently have EMI Thunder Exhaust with the cast risers. The manifold to riser gaskets has slotted holes for the cooling water to pass into the riser and out. I suspect some internal leaking, and want to switch to the gaskets with no water holes and use the jumper hose from the manifold to the riser. However, I would end up with an extra set of hoses from the water outlet/thermostat housing that went to the exhaust risers with no place to terminate. Obviously I'm overlooking a very simple solution. Where do those hoses that go to the riser now go if that opening is now being used by the jumper hose? I'm thinking it most go down to the small openings in the bottom of the manifolds via a header? Also, I would like to pick up a good set of SS risers. I'm not sure the cast ones are doing the job.

You should check out my web site. It has a lot of information on Mercruiser thermostat housings.
www.mooreperformance.org
Sincerely
Dennis Moore

Dennis, is there a performance gain with those GLM manifolds that you have on your site?
Family and Performance Boating mag had mentions them in an article on exhaust manifolds. They seemed to like them but only metions perfomance gains on the Harding/Cyclones they installed.

I have tested quit a few different boats and have always found an increase in performance by installing these manifolds. The real difference is in the quality of the castings and the corrosion resistance. The castings are very nice without any thin spots and they are dipped in hot galvanizing. I wouldn't hesitate to say that they are the finest quality cast iron manifolds on the market (including the original Mercruiser manifolds).
They are an excellent choice for salt water boats.
Sincerely
Dennis Moore

My Gils use a y-pipe to connect the 2 hoses from the thermostat housing.

formula31,
Thanks for answering the question! I thought about that also, but I have not seen any pictures of anyone using that arrangment. Where is the tee/Y located, up near the thermostat housing or at the manifold? Did you get your new engine block yet?

Email me your email and Ill send pictures. Cant post them here. So far I have a steel crank and eagle rods and Im picking up an engine south of Flint next week that I should be able to use the block and heads from.

What about the water preasure? Wouldn't this cause your water preasure to go way up? Can you just dump the unused T's over the side?

Jon

Audiofn,
Yes, it would seem you would have an increase in pressure, but it is an open ended system, so I don't think it would hurt anything. Eddie Marine told me that they have discontinued running the cooling water up through the riser and only use the jumper hose arrangement. I guess I should have asked him their recommended plumbing, but I think formula31 may have the answer.

I had the Gil's with the T fitting at the riser and my water pressure was 20lbs at WOT. When I switched to my CMI's, my water pressure dropped to 16lbs.