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Up-tune 6.2L from 300 HP to 350 HP

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smserv

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Buying a new Sea Ray Boat. Standard engine is a Mercruiser 6.2L @ 300 HP. There is a very expensive option to go to 350 HP using the same engine which I would like to do due to boat weight and passenger capacity but the price is pretty extreme. There are no differences in the specs and I am told by Mercruiser the only difference is the ECM. They get 50 more HP with a different ECM? I find that hard to believe having worked on a lot of engines in my time, but that's what they tell me and that's what I have read is possible. Someone in another forum said the props are changed also. Don't know if that is true or if that would help.
So I am asking if anyone has knowledge of this topic. Is it only an ECM that does the job? If it's only the ECM, then can an ECM for the 350 HP be slapped on to a 300 HP engine without a problem and get 50 more HP? Is something else required? Mercruiser was not much additional help.
 
This is just me but I doubt you'll save any money trying to "roll your own" on the ECU up-tune. You'll find the ECU that you want to "slap on" costs a crap ton of money.
 
Before you throw down on any boat you should be sea trialing the heck out of it. Do side by side comparison of both engines in same boat and decide if it's worth the extra.
Honestly, as Jeff says, the thing that will make a difference is engine size. Bigger engine, more power. Unless this SeaRay is under 25 feet, you will want either turbodiesel or big block power. A 2019 25 footer needs a lot more oomph than a 1989 25 footer just cz the build em fatter now than they used to.
 
Jeff is correct!
Look closely at the RPM where the HP ratings are taken, and then also look closely at the Torque rating that corresponds to a given RPM.
 
The 'extra 50 HP' may come from a different tune.....but they don't tell you the rest of the story - At what RPM which rating is achieved.

Personally, I'd just go for the 8.2L and not mess with the 6.2L.....there is no replacement for displacement when it comes to generating torque for a marine application..
 
Hp is a function of torque x RPM. Torque is a function of CID displacement,( since torque is related to psi chamber pressure x piston top area ( CID). Much of the HP gain that you get from an ECM upgrade comes from spinning the engine faster. Torque is what turns the prop. Or as they say on "the street"....There's " No replacement for displacement"..... although a big a** blower on top of the engine comes in a close second. :) :)
 
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So does nitrous! But, let's get serious here, if you want a bunch more performance you'll need a bunch more motor.

Jeff
 
smserv said:
Buying a new Sea Ray Boat. Standard engine is a Mercruiser 6.2L @ 300 HP. There is a very expensive option to go to 350 HP using the same engine which I would like to do due to boat weight and passenger capacity but the price is pretty extreme. There are no differences in the specs and I am told by Mercruiser the only difference is the ECM. They get 50 more HP with a different ECM? I find that hard to believe having worked on a lot of engines in my time, but that's what they tell me and that's what I have read is possible. Someone in another forum said the props are changed also. Don't know if that is true or if that would help.
So I am asking if anyone has knowledge of this topic. Is it only an ECM that does the job? If it's only the ECM, then can an ECM for the 350 HP be slapped on to a 300 HP engine without a problem and get 50 more HP? Is something else required? Mercruiser was not much additional help.
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Yes possible I had it done by Simon Motorsports. Not sure he still does this modification. Mercury was starting to crack down on these aftermarket tuners. On my Glaston 205 top speed before flash was 52.5 mph. After flash gained 7.1 mph. Top speed now 59.6 mph. All recorded on gps. On new engines very easy to restrict power via software. New engines have a drive by wire throttle body. I suspect on the 300hp version you are only getting 85% throttle but on the 350 hp you get 100%. Both motors are the same with tune being the only difference…. Remember computer controls the throttle body and you are only requesting and it give you what has been factory programmed.
 
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