Hey guys, I'm looking for some info on tuning/flashing a mercury 4 stroke. I spoke with Simon Motorsports in California and they said they can no longer do it.
So my question is, does anyone know where one may be able to get a 250R Merc 4 stroke flashed or tuned for more power?
Another question I have is, if I can't get it tuned, can a person simply buy a ECU/ECM for a 300R and install it on a 250R?
I certainly appreciate any advice.
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I doubt you're going to find anyone that's willing to modify these PCM's at this point, as it's illegal AND a violation of copyright laws.
Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
Still consider myself a "Marine Apprentice" after 47 years (learn something new every day).
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Looking for a bootlegger I reckon...
Flashing a Mercury is not like flashing a Yamaha. With a Yamaha, the blocks, porting and everything is the same except the ECU tune. Everything is different with a Mercury except the engine displacement. In the past there were some legitimate upgrades you could do with a 135 Optimax to make it a 150 and a couple of other examples in smaller HP as well. The big motors never had gains that made it worth the $ IMO.
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2020 Basscat Caracal
2020 Mercury 225 ProXS 4s
Originally Posted by 06 SB
That’s not quite true anymore with the new V8’s, other than cosmetics, the engine and components are all the same except for the ecu. The 200/225 has a 64mm throttle body and the 250/300 has an 80mm TB, that’s it.
Im sure someone will chime in and say R motors have stiffer mounts, or you can get different lower units, that’s not what the OP was asking,
2018 TRX 18. 2020 Mercury 200 Pro XS V8
The only engine related difference I can find between the 250PROXS and the 250R is the ECU.
Only difference I can find between the 250R and the 300R is the ECU and the intake.
Makes me think it wouldn't take much to bump either one up..
Last edited by fishnfireman; 03-09-2022 at 03:40 PM. Reason: DA
back in the day, I had a 2005 Verado, On a 2006 Procraft 210 Super Pro. Sent the PCM/ECU (not sure which it was) off to Simon motorsports, when I got it back it was 330HP.
Did it make a difference, absolutely.
Are the intake camshafts identical as well between the 250R and the 300R? Does the 250R have an oil cooler? (that would not affect HP but longevity at higher rpm). If I had a 250R, (I have a 300R) personally, I would not flash my ECU and jeopardize my warranty. On the other hand if I had a 200 Yamaha, and the warranty was expired, and I could flash it to 300+ HP for say $1000, it would be a no brainer. That alone would make me consider a Yamaha for my next purchase which would be a TriToon.
I am pretty sure the camshafts (maybe just intake camshafts) are different between the XS and the R. I don't know if the 250R and 300R has the same camshafts but I think the part numbers are different.
Lots of conjecture involved in a lot of this- a lot of which is actually true.
The 250XS and the 250R share virtually NO common components.
All that said- the PCM's are serial-number encoded-specific, with proprietary (copyrighted) software, so it's not really something you're going to want to get involved in.
Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
Still consider myself a "Marine Apprentice" after 47 years (learn something new every day).
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http://www.bbcboards.net/showthread.php?t=1020263
That thread is for a 250 PRO-XS Fourstroke.
The only "250XS" models were an Optimax model.
Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
Still consider myself a "Marine Apprentice" after 47 years (learn something new every day).
Mercury Parts, Mercury Outboards, Smartcraft & Accessories, Injector Service, TDR Reeds- BBC Sponsor
MY bad ! Intended to ask about 4 stroke.
thought both of these threads were about 4 strokes..
Last edited by fishnfireman; 03-09-2022 at 03:38 PM.
I have been wondering the same. If you swap a 80mm throttle body on a 200 and put on a 300 Pro XS pcm what would happen? Let's put the you'll void your warranty or Ecu tampering is illegal discussion aside.
Will it run?
Other question is if you can swap on the 80mm throttle body on a 200.
Don do these motors run open or closed loop? If they're closed loop then you should be able to put the larger TB on and the motor will adjust fuel trims for the extra air.
You have to take this with a grain of salt as we're literally trying to compare several HUNDRED unique models when we discuss "200-300hp V8 Fourstroke Outboards".
In general, the mechanical differences are the flywheel cover and related hardware, ETC and related components, and intake/runners.
Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
Still consider myself a "Marine Apprentice" after 47 years (learn something new every day).
Mercury Parts, Mercury Outboards, Smartcraft & Accessories, Injector Service, TDR Reeds- BBC Sponsor
I have been asking, and asking, and asking this question and never seem to get a straight answer. I don't know about the R motors but Ive been doing a ton of digging on the 200-300 Proxs and have spoken to someone who has done this personally with success. Take it with a grain of salt but I'm putting an 80mm TB on my 200 ProXS and am on the hunt for a Mechanical 300 ProXS PCM.
I've been told by a Mercury dealer, that the only difference between a 4S 250hp and 300hp Pro XS is the ECM, so one could get a 300 ECM and put it in a 250. As for the 250R and 300R, Im not sure if that's all you need to do.
Illegal and potentially subject to substantial fines and penalties (both civil and criminal). Additionally, PCM's are normally encoded for the serial number they went on.
Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
Still consider myself a "Marine Apprentice" after 47 years (learn something new every day).
Mercury Parts, Mercury Outboards, Smartcraft & Accessories, Injector Service, TDR Reeds- BBC Sponsor
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