Marine Exhaust?

[dsproshop]

I finally am building the transplant piece for the check..... 454 .040 over 10-1 pistons aluminum heads blah blah blah.... little bit over stock not tooooo bad...... I hear running a dry exhaust will pick up power vs a wet exhaust...... also wanting to eliminate the possibility of a water inversion if I do choose the monster lift cam.... does anyone have pros or cons to doing this and if I did it I would put pipe bungs in the collectors to cool the rubber hose! HELP PLEASE..... I know Gimme Fuel has some type of insight on this situation! ! !

 

[Gimme Fuel]

All depends on how much cam you want to run. Yes full dry will gain power because you are picking up exhaust flow and pipe volume that is occupied normally by the cooling water entering the stream.

Full dry Pro:
-Make more HP
-no chance of reversion

Full dry Con:
-LOUD!
-Need custom tails and/or will be cutting/modifying holes in transom.

You can find plenty of reasonably priced full dry manifold setups on OSO. I would at least do the long (19-20") risers for what ever performance manifold you choose. that gives you quite a bit of cam choice and big sizes utilizing a short piece of hose and existing tips. This is what I currently run but I will be having my existing tails extended thru-transom dry in the spring.

As far as cam goes, Call Bob Madera at Marine Kinetics. He is a wealth of knowledge and his parts prices are at least same and sometimes better than big box stores. He will help you develop your whole package even if you only get cam from him. He is the guy to talk to BEFORE you start buying a bunch of parts. I could have saved a bunch of time and money if I did that first, haha. He will tell you exactly what HP you can make with what exhaust scenarios.

BTW, if you want 100 mph, think around 1000 hp goal, haha.

 

[23outlaw]

I used the center rise aluminum manifolds with a stainless riser (dry exhaust to the tip of the riser) from Eddie Marine. I put them on my 78 Convincer with a 355 and a medium size cam. I think for the money, this is the best way to go as will free up some horsepower and allow the motor tobreath without the danger of water reversion.

 

[dsproshop]

If possible can you guys post a pic of your set up..... I was actually thinking about using a set of upset turbo headers and welding a pipe bung into the either collector or riser to cool tubes and exit seawater from closed cooling system.....

 

[Gimme Fuel]

These are EMI Thunder manifolds with the 20" long standard risers with an oxygen sensor bung welded in each one.

 

[23outlaw]

My exhaust looks exactly like Gimme Fuel's. I lke the fact that they make good HP and are not the individual tube style ( like CMI uses) that can develop cracks over time and leak water into the motor.

 

[Wrenchmate]

A lot of headers or performance exhaust will say fits standard Bravo application and
thats usually a pretty close if your tips are 27'' centers and I think yours
probably are. The older Convincors were 19'' and I had to modify to make fit because I wasn't going to cut new holes in transom. Yours should be a little easer. These were standard Bravo and probably would have fit your boat. Now they will fit only the older 251s. If you order new they can make them to fit from the company but thats really expensive. As far as the rubber exhaust hose getting to hot mine never has and Ive had two different brands of headers on here. The header tube is only about a inch away from the tip so your seeing more hose on the outside than whats exposed on the inside plus the water is exiting the header right there. And like Gimmie said this is very very loud and very very cool.

 

[corey331]

I have measured my 253 for a set of custom headers on my new motor and it is standard bravo exit through the transom, which will make it a lot easier for ya to order something. On my new motr, since I have to have something custom made anyways, I am going with a header with long tails all the way through the transom and keeping them dry to the tips so I can get pretty aggressive with the cam. I know its going to be stupid loud, but on my home lake there isn't any kind of sound ordinance so I'll be good. My girls will just have to wear ear plugs when they go tubing behind it, lol.