for you guys that have messed with a 25 tantrum.raced my buddies 25 checkmate with 502 mag and we are dead even.anything quick and cheap i can do for a couple mph.stock 454 mag carb.could only spin my 25 mirage 4500 rpm.could lab it for 200 and would like another 2-300 rpm.thinking of emi thunder exhaust.would this help or should i put the 1500 somewhere else.and please don't say blower

Emi thunder is good for 25-30 HP, not sure how much more speed, labbing will help, what about a set of headers out of the classifieds I would think that would be your biggest gain..

Save some money, buy the Revolution Marine exhaust, get a good air breather, have your prop labbed, look at your balance and make sure you're not using your left tab too much, run some good higher octane fuel and advance your timing, take ALL the excess weight out of your boat, check your skeg for notches, chunks or other problems that may effect hydrodynamics, take off your speedo pitot pickup,
I can think of a few othere, but start there and see how things work...

Hey...you sound like you know WTF your talking about!!

gordo how much timing can you go with higher octane fuel.sending my prop out to bblades today.not sure which exhaust i will buy.i like the emi,should just supercharge and be done but had alot of problems with my other boat with a blown smallblock.thanks for the input

Gordo, RM over Stainless Marine?

For the money, you Can't beat the revolution Marine exhaust. The engine guys may have a more exact number for you, but running 94 octane or so @ about 40* total advance seems to work well. Anything more than that (fuel octane or timing) seems to be wasted due to the low compression ratio. The balance/weight I mentioned refers to the boat leaning to the left due to prop torque, load balance and other issues that cause drag or poor handling. Keep in mind, these are all things that will help you a half a MPH at a time. Add them all up and you can get a couple of MPH for free.
A great friend once told me, "It's not always how fast you go, but how you go fast".

<laughing> I read a book once....

WOW......I can't read, I just look at the pictures

Gordo is also referring to balance, as make sure the fat guy to your left isn't throwing the balance off either. Ha Ha....

I do agree the exhaust from Revolution is really good compared to EMI. Never had an opportunity to compare it to Stainless Marine thought. Probably pretty comparable.

A.B.