Yamaha F90 to 115 conversion ?

[klbowe]

I had heard somewhere that my F90 Yamaha (not fuel injected)

is the same engine as the 115 but dumbed down with a chip ? Just curious if anyone has any information on this or if it would be worth the conversion .

[Whoaru99]

Almost seems like there would be more to it than just a chip. Being non-fuel injected I don't know what, other than timing, could be controlled by computer to make 25 more hp.

Maybe, I guess; but almost sounds too good to be true.

[PerchJerker]

I know someone who was talked into converting his 25 hp into a 35 hp by having the carbs rejetted. Big mistake, cost him some money and the motor never worked as good as before the conversion, and he didn't get any more top end out of it. Maybe not the same thing as you're talking about, but I wouldn't do it unless you hate your motor. Even then I wouldn't do it.

[Valv]

I don't think you can change much from a carbed motor.

You might have to change jets etc.

Cost might be: high

risk of problem: high

gain in extra speed: very little (2mph/3mph)

I honestly wouldn't do it.

[DRH1175]

I have heard it is the same block only bored out a tad different. I really don't know. I have the f115 it is one awesome motor on my 1700 explorer. If you look at the specs it has a few more ci than the f90. I will tell you this if you are trying to figure out if there is a power difference I will tell ya hell ya. My friend bought the f90 for his explorer last year wasn't happy with it. Upsized to the 115 and not even close you really notice the 25 ponys!!

[196thDLR]

There is a cubic inch difference between the F115 and the F90, 106.2 to 97. There is a compression difference I believe also. Weight is also different 402lbs to 369lbs.

The two motors that specifications are alike are the F90 and the F75.