I have a pair of Mercury 250 EFI's and want to performance tune them. Anyone know anything about tuning these motors?
I have heard about a company called Magnum that has a system for the ECU. I also heard about modifying exhaust.

Any info would be appreciated..

He's on the other side of the country but he is one of the best for the 3.0 liters.

http://simonmotorsports.com/

What are you looking to achieve? I recommend starting with setup! Get the most you can out of dialing the boat in then get into the engines. We can take care of any thing your boat needs. Been doing this for 30 yrs. Please feel free to give us a call @ 302-368-2860

This guy in homestead is really into 3.0ls Definitely would give him a call...


http://forums.screamandfly.com/forum...d.php?t=202231

Be very, very careful. If you intend to use these motors for normal, dependable boating, simply keep them properly maintained acoording to factory standards, and stay away from the "tuners". Those guys are great for people interested in top speed, but adding RPM, HP, and stress simply reduces engine life. If you and your family are miles from home with a blown up engine, it is of little comfort that you gained 2.5 mph a few weeks prior. Do as the previous poster suggested, go over your setup, propeller selection and weight distribution and leave the engines alone.

T2x

Thanks everyone,

Just was thinking about it rather than the cost of new engines.

Yeah if money wasn't an object like a couple years ago, a pair of 350 Verados would be nice, or hell I'll make it a triple...

I was only thinking of some minor adjustments to gain or tweak a little more hp. Some say the motors I have 2005-2006 250 EFI's put out around 275hp?
So I was andering how to get closer to 300hp and not have to change motors.
Perhaps some combination, running 93 oct, changing plug wires, plugs, ECU reprogram, exhaust, etc. I wouldn't want to start boring or any block mods.
I did cut out the blue part of the Decals and that made them feel faster.
Who knows I'll probably leave all alone, they do run great!

Marty at Diamond

http://www.diamondmarine.com/

thanks Brad,

I will give Marty a call. He is also right in my backyard.

Thanks

Kurt

I'd imagine you can swap out with factory 300 promax ecu's intakes, reeds, heads and have no problem with reliability

i would recommend talking with Jay Smith. http://www.jaysmithracing.com/ There are many things you can do to improve the performance of your motors and not dramatically reduce reliabilty. Two things you can do is port the horn/ reed plate and dry stack the exhaust. Both are very economical and don't mess with compression, rpms or fuel curves.