my buddy has a 27 awesome cat we just put his new engine in and the water jacketed tails on his CMI stainless headers dont have enough drop to fit the transom cut outs for the exhaust. they are about an inch and a half to high.

the questions are:

1) do the tails have to be water jacketed or can i make my own stainless tails and run em dry with the water going over board from the header outlet? or if i make my own tails do i need to weld in a bung for water to enter them?

2) where and how much should he expect to pay for a set of tails that will fit his application. also how do you measure and make sure you get the right ones when he does find some or decide to buy new ones?

Yes they absolutely have to be water jacketed. If not they will start the transom on fire.

Order custom tails from CMI.

+ a million what Griff said. Get the right parts for the job! Fires on the water is no joke.

lol thats all i need to hear to convince me. lol

i was sure there had to be some kind of hazard running them totally dry.


Question: what about injecting the water into a stainless tail?? hence a water injected tail rather than a water jacketed tail????

i know water injected headers stay really cool and dont have much problems.......


thanks for the info guys!

Just send the stock tails into CMI and have them modified.

They must be water jacketed in a closed engine compartment. Even dry tails are water jacketed.

If you need new tail pipes you can mock it up with pvc pipe and then send that to cmi and they will make the new pipe exactly the way it needs to be. Just and idea

It is a lot easier to cut new holes in the transom and patch the old ones. Faster, cheaper.

ok.

forgive my questioning, but if all tails must be water jacketed then whats the difference in the the stock exhaust that Mercruiser uses, in most cases either a straight stainless pipe clamped on both ends by rubber boots or simply a rubber hose, that goes from the manifold riser where the water is injected to the exhaust tips at the transom. hence a "water injsected" wet tail pipe and not a water jacketed tail pipe.

just wondering......im gnna do what is right...but at the same time i understand that there is often more than one way to skin a cat and still be safe and functional at the same time.

reversion wont be a problem.....so why couldnt i run "wet" tails with the water being injected into the tial pipe at the joint where they meet the riser......just like stock merc stuff???

the point being that i have the material and can make my own tails for almost no money if this idea will work.

Merc stock exhaust dumps it at top of the 90 in the riser so tail or rubber boot is cool. Cmi runs a jumper and dumps at end of tail, but the water runs in the whole tail so it keeps it cool. No real way around this. Many have tried to think or try a way around it and char grilled their transoms. You can bend the cmi tails to a point.

I guess you could do it that way, but its a good waste of a pair headers and defeats part of the purpose of having them. Anybody that sees it will think its a cobbled together system. It may even revert water on a stock engine. On stock Merc cast stuff, at least the water is directed toward the stern under pressure and into the exhaust fumes.
Also, that is not "water injected" per se. That is just wet exhaust. Water injected is like what is used on jet boats.