# Mercury 4 stroke from 75hp to 115hp



## jrhall (Feb 7, 2014)

So I have been told that the Mercury 2010 75hp, 90hp, and the 115hp 4 strokes are identical except the 115 has a little different gearing. The only difference is in the programming in the computer. A company in California says they can reflash the computer and bump the 75 to a 90 or a 115 with no other changes except removing a restricter in the air filter. This would be great when adding a jet drive to a 75 making it a 115, which in theory would make it an 80 hp at the foot. There is not much information on this and I was wondering if any of you had ever tried it or knew anyone that had? According to the spec sheets on the 3 motors they are identical so it makes sense to me.
Please leave comments


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## Country Dave (Feb 7, 2014)

_That is not entirely true,

Most manufactures build their smaller OB on the same platform. It’s true that a lot of the HP comes from the tune. The tune being “The software” in the controller/module, not really any deferent than most modern autos. 

It controls base timing, valve timing, injector on time/duration and a host of other changes at deferent RPM ranges. You can bump up the HP by remapping the controller; however it’s been my understanding that Mercury, Yamaha and others are making the HP higher from the same displacement blocks by having changes in the heads, not just different programs in the controller. 

Heads with bigger valves, different combustion chambers etc. A 2010 Mer 75 HP and 115 HP may have the same displacement blocks but the majority of the HP difference is in the heads, “not just controller mapping” _


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## jrhall (Feb 7, 2014)

I thought that too about the heads, but when you look up the part number for the head assembly they are the same part number for the 75 and the 115.


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## Country Dave (Feb 7, 2014)

_Totally not sure about that,

Anything is possible. I would try calling Merc directly, don't call a dealer that will just be a waist of time. I would also call or email that company in Cally and ask them. _


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## lattehead (Feb 8, 2014)

same part numbers and same weight on the engines regardless of the hp. the extra hp is in the restrictor and ecm mapping.


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## Lil' Blue Rude (Feb 8, 2014)

guessing the company is Simmons? If it is you might go check out screamandfly dot com I'm pretty sure someone from simmons is a member there and I've seen them talk about reflashing the computers. If I had a 4 stroke I'd probably see what they could do for one. Did you check the part number on the cam to?


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## jrhall (Feb 8, 2014)

Yes it is Simmons, I spoke with them on the phone and they assured me that re flashing the computer is all that needs to be done, and it will have the hp of a 115. I also have to remove that restricter piece. Seems a little to easy. I would love to talk to someone that has done it. Thanks for all your comments.


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## Country Dave (Feb 9, 2014)

[url=https://www.tinboats.net/forum/viewtopic.php?p=341270#p341270 said:


> jrhall » Today, 00:08[/url]"]Yes it is Simmons, I spoke with them on the phone and they assured me that re flashing the computer is all that needs to be done, and it will have the hp of a 115. I also have to remove that restricter piece. Seems a little to easy. I would love to talk to someone that has done it. Thanks for all your comments.



_
Brother that's way cool,

More ponies and less weight, win win........................... :mrgreen: _


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## DrNip (Feb 9, 2014)

Give it a roll and let us know.


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## Boat2fast (Feb 21, 2014)

[url=https://www.tinboats.net/forum/viewtopic.php?p=341245#p341245 said:


> Lil' Blue Rude » 08 Feb 2014, 19:16[/url]"] Did you check the part number on the cam to?



Again, did you check the Camshafts(s)?

A quick look at the parts page shows the same intake camshaft for 75 thru 100hp. And a different intake cam for the 115hp. Exhaust cams for all are the same, only the one number.

That was just a quick look and I didn't have your actual serial number. Check the camshafts. In a fourstroke, it's all about the cams, compression and intake/exhaust tuning. Computer mapping has to be tailored to these factors.

Check other things too: inner exhaust (tuner), intake manifold, throttle body, whatever is there.


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## Charger25 (Feb 21, 2014)

I'm gonna go with Boat2fast on this. Its hard to believe that you can get 40 extra hp just by a flash on the program. 10 to 20 extra hp maybe.


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## jrhall (Feb 21, 2014)

Looks like you are right about the 115 having different part numbers for some internal parts. It looks like they only sell the 100 over seas. I would be happy going from 75 to 100. Its just an idea, I may try it but I am waiting patiently for my jet drive to get here. I hear they are 9 weeks behind making them. Its been 2 so we will see. Thanks everyone for your comments, I will keep you posted.


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## jrhall (Jul 26, 2015)

I know this post is old, but I finally sent my ecm off to be programed. Here is what I have .....
Before 4900 rpm, 23 mph, fuel 6.4 gph
After 5400 rpm, 30 mph, fuel 8.8 gph
Planes quicker and uses less fuel at lower speeds. Before at 23mph it used 6.4 gph, now only 6 gph at the same speed.
Was it worth it? For me, yes. I would do it again. I don't think it runs like a 115hp, but it does run better than it did. I lost a lot of power when I swapped over to a jet and this seems to have gotten it back.


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## Lil' Blue Rude (Aug 1, 2015)

Cool thanks for updating your post. Surprised it gained 7mph from 500rpm figured it would have taken more to see those kind of gains.


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## mattfish11 (Mar 2, 2016)

jrhall said:


> I know this post is old, but I finally sent my ecm off to be programed. Here is what I have .....
> Before 4900 rpm, 23 mph, fuel 6.4 gph
> After 5400 rpm, 30 mph, fuel 8.8 gph
> Planes quicker and uses less fuel at lower speeds. Before at 23mph it used 6.4 gph, now only 6 gph at the same speed.
> Was it worth it? For me, yes. I would do it again. I don't think it runs like a 115hp, but it does run better than it did. I lost a lot of power when I swapped over to a jet and this seems to have gotten it back.


I know this is an older thread, but just curious how you like the upgraded/flashed ECM? How is the motor running? I'm also considering this type of upgrade...


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