mung272

how do the plugs look? is it running lean; did you add fuel? change intake and add headers?

These heavy hulls love trim, cant get enough. try more trim

My 272 w/ 330hp's pulls 65 at 4900 with 23p 3 blades any load any water- and I love how easily it comes out of the water and midrange. With 25p I can hit 68 at 42-4300rpm but its a pig coming out of the water.

thats with 330hp's - you should be getting more than that...

I have some 25p props for sale btw...

Soflow1

That cam is HUGE! Way too much for your application and stock mercruiser components. As installed, I would expect your engine to make less power than a stock 454 mag across almost the entire rpm range.

Jg1000

iTrader: (1)

Yeah , so what is the best upgrade ? I'm thinking ported 496 exhaust and maybe port the heads and intake ? New cams isn't an option...

Car Biz

iTrader: (1)

That is a great cam if you have the intake,heads and exhaust for it. FYI i have the XM 270 H with AirGap intakes, Dart heads and Imco exhaust. I would have prolly made more power with the cam you have. Do you have a true mag as in rectangle port heads?

Escrowdog

Ya, but it sounds bad ass at idle...which is really all that matters at LOTO.

Once you leave the dock you're just another dumb ass out driving too fast, riders on the sunpad, throwing occupants around....EVERYONE knows this...now.

Soflow1

Your not thinking anywhere big enough, a ported 496 exhaust isn't going to get it done. Are you prepared to spend between $8000 and $10,000 dollars in bolt on upgrades?

If not, I strongly encourage you to rethink going back to the stock cams or something much closer to stock.

Jg1000

iTrader: (1)

Yeah this is a true mag , forged short block , rectangle port heads, high rise aluminum manifold.

I said that changing cams out isn't an option because I don't have the facility to pull the motors. When the starboard motor ate a cam lobe my boat mechanic felt sorry for me and let me use his shop to fix it, which even then I had to over night the cam and get the whole project done in a very limited amount of time.

So I am just going to have to make the best of the situation. What limits rpms on these mag motors ? I have valve springs, I'm sure the rockers are good for 6k. Can the stock bottoms ends be spun to the 5.5k range?
Maybe I should just save my money on gaskets and exhaust and just shove more air down its throat with a Vortech ; ) I'm sure with 5 psi through a properly sized vortech I could max out my bravo 1's .

Jg1000

iTrader: (1)

What power are you making with your setup?

I quickly have realized that when wanting to upgrade twins it is crazy expensive. So I think that aftermarket heads are out of the question, but porting the stock heads is viable and probably flow pretty well being that they are the rectangle port.

Car Biz

iTrader: (1)

446@5400

497ftb@3600

and yes porting the heads will help!

i don't run mine past 5500 i'm sure the bottom end is good for it but no sense in building a motor to run that high if you don't have to!

Jg1000

iTrader: (1)

Yeah I totally agree. I want to spin mine up to that range to see if it makes more power.

What dart heads do you have ? Are those numbers at the flywheel ?