Maybe a foolish question but here goes..
I am replaceing a 454 mag with a 540 motor.
Exaust system is a Eddie Marine Thunder model with stainless risers. My old exaust had a provision on the risers for hose return. The Thunders do not, should I change the thermostate houseing to a single one or I am I not understanding something here.
thanks
Sheikman

You say that your "risers had a hose return". That confuses me. Unless I'm mistaken the only time water was being returned from the exhaust system was when the exhaust was used to preheat the engine. I don't think Merc ever sold any engines with that system. Most of the time the water enters the bottom of the manifold, and passes thought the gasket into the riser where it gets dumped.

sheikman. I think what you are saying is that you have 4 hose outlets on the factory t-stat housing and 2 outlets went to the risers and 2 went to the manifolds. With EMI's, you only need 2 outlets. You can T the outlets on each side of the t-stat housing together or get one of the newer style housings. EMI also makes an aftermarket housing, but its about 200 bucks. Post something in the parts section and you may be able to find a good used on from someone who switched to a crossover system.

If you are looking for 454 cooling components I have what you are looking for.)

Hey Griff,
Thanks for the reply. My terminology was comming out ass backwards. Yes, I saw the housings in Eddie Marine. Didn't think they were 200.00 but what the heck. Nothing has been cheap on this project. Keep on spending!!!!

Sheikman,
Have a buddy who tried the SS t-stat housing from Eddie, didn't work out well at all!
Huge fluctuation in temp.
Install a universal t-stat housing available from Ward Marine (made by Barr)out of Winthrop Ma. (617)846-1421 and ask for Gary or www.wardmarine.com..
When it comes to great prices and very good service on general marine supplies, they are great.
I have used two of them myself to solve the exact problem You are facing. They are a nice neat piece and will keep temp very steady.

Sheikman,
My buddy has a 1989 242LS with a 540ci.
Same swap You are making.

I checked the EMI book and they are actually retailed at $120.

i took off the y fittings off when i went to a blower, i can send picture email ,if interested,have all hoses and clamps and extra hose,let me know