Tuning Mercury Outboards
 

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!
http://C:\Documents and Settings\Kur...p\IMG_0459.jpg
http://C:\Documents and Settings\Kur...p\IMG_0458.jpg

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.

I can do the 250EFI as long as its the later PCM. More rpm and spark.

what gains in hp can you expect from some of these mods?

can you get 50hp more out of each motor and not affect reliablity?

25-30hp more. 50 would a bit tough. Not sure what the differences are between 250 and 300, but you could upgrade it and we can upgrade the cal.

Can anybody in US/Canada help me to tune the ECU on an 350 SCI 2010 mod to 400hp?
I know it's possible.

what about also adding hydraulic jack plates to the motors,
what kind of performance can you get?

Well said Rich!
Jr.

For those hardcore outboard peeps, there is one other alternative to a performance tune that hasn't been brought up yet.

About 15 years ago I worked with a company called Hydrodynamics and installed a nitrous oxide system on two 1993 Mercury 2.5's 245 HP carb engines for my 22' Talon. Sent Hydrodynamics the intake manifolds and they installed the spray bars. Used a separate fuel cell to hold a 32:1 alcohol and 2-cycle oil (castor based) mix as the enrichment fuel which was injected when the nitrous was activated. The nitrous could only be activated at full throttle. Started rich and work my way to a perfect tune using Pyrometers and reading plugs. Had several safety measures including a low enrichment fuel pressure safety switch that would deactivate the system in the event of low fuel pressure. The system gave an additional 110HP per engine at the touch of a button. One 20lb nitrous oxide bottle lasted a long time. The additional power was amazing and for the impromptu river racing I was doing back then, it was a BLAST!

I had over 250 hours on the engines before selling the rig and had no nitrous related engine problems. When done right, nitrous oxide can be an ultimate upgrade to a high performance outboard.

http://www.hydrodynamics-usa.com/nitrox/index.html

Call Eric he will make the most reliable HP for you on the 3.0 litre motor.


Dan

Diamond Marine
 

X 2 for Marty at Diamond. From mild to wild.

where is Diamond, Marty contact info

what kind of costs?

never mind just found on previuos page

Know Marty well. He does an awesome job on 2.5L.

FYI he will not touch a 3L. Been there done that. Call Eric Simon at Simon Motorsports. Had a 31' Fountain with 225hp 3L and ended up with close to 300hp. Motors ran great never had a problem with the powerhead. Just keep in mind the motor mounts and mid section/lower units were not built for 300hp.

You can also a Brucato intake system that gave my boat another 30hp.
In the end we had Boysen Reeds, Heads, 300x PCU/ECU's Brucato Intake System/ Coils and wires.