hp from exhaust ?
 

when a exhaust manuf. claims say 10%hp gain from exhaust does this mean a gain of hp at the flywheel or from the prop shaft ?

it means they are full of it!

YUP

It means that stock manifolds flow crap, and 10% better than crap is still crap. Save the money and buy headers.

Don't even waste your money on headers...unless you are changing heads, intakes, carbs and cams at the same time. I learned that valuable lesson. Headers might give you a mile or two per hour for the $3000 to $4,000 you spend per motor. Unless you are ramming a lot more fuel and air into the top of the motor, you don't need to push it out the back any faster. It just doesn't payoff. Once you add the other items however, headers are a necesity.

Well put Curt!!!

Exactly the advice I was given , but a set of Stainless marine manifolds couldn't hurt !!

1 mph was'nt worth it but the sound and looks were;) :D :D :D

Louder is better.
Randy

Loud pipes save lives!

Sound and looks!!!! Also better reliability. Good to get away from the Merc crap!

I installed Stainless Marine and got better midrange punch, less black soot, and the sound was awsome!

Merc exhausts are nothing but CRUDE dudes!!!
 

I agree with most of what Curt has said. An aftermarket exhaust system may not give you much initially in the way of speed/performance especially for the $3K-$4K spent, BUT it IS the best thing a person can do BEFORE he starts adding other speed components to the engine. Induction type items such as cams, heads, carbs, intakes manifolds, etc, are NOT going to help much while retaining the STOCK exhaust manifolds. What a person tries to put into an engine through induction needs a smooth unrestrictive way out as well. This can be done through a set of aftermarket exhausts, THEN the MORE you do to an engine the MORE the aftermarket exhausts are going to work for you.

If you CAN'T afford to do all at once, here's an idea of what you can do: Buy the aftermarket exhausts FIRST and install them on your boat for the first year. They will enhance your engines, sound better and will USUALLY improve your fuel econ a bit and midrange cruising and you may also find that your RPM will go up slightly and maybe a slight increase in speed---maybe 1-2mph if that.

The next season, you can start adding performance components to the engine(s) and as you do, each time you do something your engines will be more sensitive to the changes because you already have the aftermarket exhaust manifolds in order for the new parts to work well.

Hope I haven't confused you any further. Best wishes :)

BTW, I would also go with a DRY exhaust system---no reversion that way and give a little better performance----but they ARE louder for sure!