I found a 115hp ECM

[DRock]

I had been planning on either buying a 115hp ECM for my 90hp or sending my ECM to Simon Motorsports for a reflash to 115hp. Today while browsing Ebay i found/bought a 115hp ECM off an 05 Mercury 115 4 stroke for $300 . It should be here mid to late week so hopefully i'll try her out next weekend.

Any ideas on what i'll gain speed wise? My goal is to cruise at the same speed but less RPM, and gain a little up top ofcourse. Currently with just me and a half a tank of fuel, it'll run 30mph gps at 5600ish rpm. Yesterday with me and my wife, it ran 29mph gps with 3/4 tank at 5,500 rpm. The pontoon is pretty light and i'm running a 13.5"x15p prop. I also have a 13.25"x17p to try if need be(it may be too much, but i can always try it). My max RPM range will move from 5000-6000rpm, to 5800-6400rpm.

So what do you guys think? 1-2 mph? 3-4mph?

[Bamaman]

I'll say you'll go from 5600 rpm's to 6000 rpm's with the same 15 pitch prop, and + 3 mph.

Change to the 17 pitch prop and compare. You'll probably be back to 5600 rpm's and +4 mph--and get better fuel mileage and have more acceleration.

You might look at the Mercury parts microfiche's online to see if there's any difference between the air intake system of the 90 vs the 115 hp. Sometimes they'll put a restriction in the smaller horsepower motor to really make a difference.

We'll be interested in your progress.

[DRock]

I'll say you'll go from 5600 rpm's to 6000 rpm's with the same 15 pitch prop, and + 3 mph.

Change to the 17 pitch prop and compare. You'll probably be back to 5600 rpm's and +4 mph--and get better fuel mileage and have more acceleration.

You might look at the Mercury parts microfiche's online to see if there's any difference between the air intake system of the 90 vs the 115 hp. Sometimes they'll put a restriction in the smaller horsepower motor to really make a difference.

We'll be interested in your progress.

Thanks Bamaman, i appreciate your input. I'll look on the parts break down to be sure. I know they used a restrictor on the 75hp four strokes, but i need to double check with the 90.

Quick question: What if what you say is true about the 17p running 5600 and +4mph. Will it hurt the motor to be 200 rpm below the recommended rpm range? Just curious.

[Bryden24shp]

200 under, nope! You'll be fine. Congrats on the find! Good Job!

[ROLAND]

just curious, I know what the upside is to the ecm reflash, but are there any possible bad effects... I"ve been thinking about doing that with my 75... as I understand it is the same size block that yamaha uses for not only the 75 but the 90 and 115. Wondered if it would be benificial for me to try and locate a ecm from a 115?

[DRock]

Well I THOUGHT i was doing good. I followed Bamamans advice to look at the intake silencers to see any differences. Turns out, on the 05/06 115 mercs/yamahas, they have a completely different intake set up. Dual throttle bodies instead of just one like my 90.

I may have had a huge misunderstanding here. Evidently in the Yamamerc years the 75 and 90 were the same along with the 100, but the 115 had a different intake/throttle body set up. Starting in 2007, when Mercury started producing their own power heads, they're all the same block from 75hp to 115hp, then the 150 and 200 verado's use the same block.

I'm going to be calling the place i bought the ECM from this morning. Still crossing my fingers here

just curious, I know what the upside is to the ecm reflash, but are there any possible bad effects... I"ve been thinking about doing that with my 75... as I understand it is the same size block that yamaha uses for not only the 75 but the 90 and 115. Wondered if it would be benificial for me to try and locate a ecm from a 115?

You should be fine by finding a 115 ecm. Mercury's 07 and up 75-115s were the same with the exception of the 75 having a restricter just before the throttle body(easily removable).

[Bamaman]

just curious, I know what the upside is to the ecm reflash, but are there any possible bad effects... I"ve been thinking about doing that with my 75... as I understand it is the same size block that yamaha uses for not only the 75 but the 90 and 115. Wondered if it would be benificial for me to try and locate a ecm from a 115?

Roland: Your engine appears to essentially be the same as a 90 hp with a different ECU flash. Unfortunately, most of the ECU flashes available are for larger horsepower very popular motors--like a 250 Verado.

A $650 ECU flash is considered a bargain to horsepower by some. I consider it expensive in that I can get any one of 140+ different flashes for my PowerStroke diesel pickup truck for $75. $650 is highway robbery if the computer program is "in the can."

Sometimes you've got to accept the limitations of an engine.

[DRock]

just curious, I know what the upside is to the ecm reflash, but are there any possible bad effects... I"ve been thinking about doing that with my 75... as I understand it is the same size block that yamaha uses for not only the 75 but the 90 and 115. Wondered if it would be benificial for me to try and locate a ecm from a 115?

Roland: Your engine appears to essentially be the same as a 90 hp with a different ECU flash. Unfortunately, most of the ECU flashes available are for larger horsepower very popular motors--like a 250 Verado.

A $650 ECU flash is considered a bargain to horsepower by some. I consider it expensive in that I can get any one of 140+ different flashes for my PowerStroke diesel pickup truck for $75. $650 is highway robbery if the computer program is "in the can."

Sometimes you've got to accept the limitations of an engine.

You're right, he can upgrade to a 90 hp. I thought for some reason that he had a merc, and that would allow him to go to 115hp with mercurys new fourstrokes.

I talked to the company i bought the ECU from and they were very nice. He offered to still send it out to me to try, but after talking to a local Yamaha/Mercury mechanic he didn't suggest it. The 115 has a different intake/throttle body set up and has a larger bore on the Yamamercs than the 90.

I did call Simon Motorsports and they said they could get my 90hp to 110-115hp still. Will still be $650. I agree that it is steep, but it looks like my only option.

I'm in the auto repair industry and have Ford's IDS software enabling me to do anything a dealership can do, including reprogramming ECU's. I know what it costs for the software and how long it takes to reprogram and that price IS steep. I just don't know of anyone else who has the capabilities to reprogram my ECU for more power.

[ROLAND]

just curious, I know what the upside is to the ecm reflash, but are there any possible bad effects... I"ve been thinking about doing that with my 75... as I understand it is the same size block that yamaha uses for not only the 75 but the 90 and 115. Wondered if it would be benificial for me to try and locate a ecm from a 115?

Roland: Your engine appears to essentially be the same as a 90 hp with a different ECU flash. Unfortunately, most of the ECU flashes available are for larger horsepower very popular motors--like a 250 Verado.

A $650 ECU flash is considered a bargain to horsepower by some. I consider it expensive in that I can get any one of 140+ different flashes for my PowerStroke diesel pickup truck for $75. $650 is highway robbery if the computer program is "in the can."

Sometimes you've got to accept the limitations of an engine.

Thanks Bama... I agree.... to me, there is no way to justify that kind of expense for the difference between the 75 and 90 hp.... Think I'll just keep on keepin on.. thanks again...