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Tuning Mercury Outboards

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Old 12-04-2009, 01:14 PM
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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..
I can do the 250EFI as long as its the later PCM. More rpm and spark.
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Old 12-04-2009, 05:25 PM
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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?

Last edited by DeepV; 12-04-2009 at 09:49 PM.
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Old 12-04-2009, 10:09 PM
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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.
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Old 01-10-2010, 03:38 PM
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Can anybody in US/Canada help me to tune the ECU on an 350 SCI 2010 mod to 400hp?
I know it's possible.
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Old 02-25-2010, 09:20 PM
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what about also adding hydraulic jack plates to the motors,
what kind of performance can you get?
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Old 02-27-2010, 02:01 AM
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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.

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Well said Rich!
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Old 02-28-2010, 02:33 PM
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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
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Old 03-01-2010, 12:54 PM
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He's on the other side of the country but he is one of the best for the 3.0 liters.

http://simonmotorsports.com/


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


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Old 03-16-2010, 07:34 AM
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Thumbs up Diamond Marine

X 2 for Marty at Diamond. From mild to wild.
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Old 03-16-2010, 07:10 PM
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X 2 for Marty at Diamond. From mild to wild.
where is Diamond, Marty contact info

what kind of costs?
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