Thanks for all the replies everyone, just as I had expected I had overlooked something. Everything looks good on paper but to actually make it work takes much more. I agree, I think a set of 496 manifolds or others will suffice. Thanks to everyone who replied. I was completely overlooking the explosion hazard. It happens when you get horsepower bound.

Check out Revolution Marine exhaust for a good bang for buck.

I agree with the above. Not only are you begging for a fire, but you'd be in direct violation of 46CFR. You'd have to have the engine totally out in the open for that to be viable.

I ran Revolution manifolds for five years on a 540 BBC (600 hp). I ran in the salt water some, and flushed immediately after running. No problems to note, and good value.

Also shop the classifieds here for Stainless Marine exhaust. It is by far the most reliable and popular and you can do pretty well if you buy used.

Keep an eye on the swap shop, there have been many good deals. Glad to see you are not going to use automotive headers. I was getting a bit nervous for you when I started reading the post. Get the approprate exhaust for your project, if you are planning a performance cam be sure to get long risers.

I will be going with the 496 manifolds and stainless risers. Has anyone tried the Borla tips on their boat?

I am replacing my stock exhaust with the 496HO manifolds and risers. Through my process of buying manifolds and risers I have one extra pair of the risers that I have removed the black powder coat and polished. $250 plus shipping if interested. I have a second pair that are polished too but one riser has a small dent. A friend dropped it. $100 for that pair.

Griff, I came to same choice of revolution marine after much research only to get an email from revolution that "sorry we are not producing our manifolds anymore." I really wanted them after so many raves about them.