yamaha 80hp to 100hp by jet change

[Hoodwa]

I have a 2001 f80 4stroke my question is it possible to bump the hp to 100 by changeing the jets. I have a factory manual which covers both motors. the specs on the motors are identical except for the carbs, f80 #67g10 f100#67f10 the carbs are identical except the jet sizes and the f100 has a midrangejet which i am shure is just plugged off on thef80. So if i changed the jets and unplugged the midrangejet do you think it possible? I have 30 years experiance working on bikes boats cars rvs. any input would be greatly appreciated.

 

[Bifflefan]

Re: yamaha 80hp to 100hp by jet change

Not sure but i would think the exhaust may also be different.

 

[noelm]

Re: yamaha 80hp to 100hp by jet change

you need the genuine parts manuals for both motors and check every part one by one to determine what is different, it would be very unusual to get an extra 20HP (25%) by just changing a jet! I reckon you will end up with a poor performing, rich running 80 if you try it. Lots of motors share common parts, and lots share common capacities, but lots of different parts, like valves and heads and so on.

 

[Hoodwa]

Re: yamaha 80hp to 100hp by jet change

I have a factory yamaha manual that covers both motors, bore,stroke,valve size,exhaust even the same props.the electronics are the same also!

 

[krisnowicki]

Re: yamaha 80hp to 100hp by jet change

I wonder if the reed assembly is the same.

 

[Hoodwa]

Re: yamaha 80hp to 100hp by jet change

Four stroke no reed valves,4 keihin carbs

 

[99yam40]

Re: yamaha 80hp to 100hp by jet change

to make more HP you need to get more air and fuel in and let it out without restricting it. I no not think dumping more fuel into a carb will not do all of that. There maybe some difference in the timing control also.
A previous owner of my C40 drilled out the jets and it took me over a year to figure out what was wrong with it , cutting out( dropping a cylinder) at WOT

 

[mphelle8vld]

Re: yamaha 80hp to 100hp by jet change

I'm sure you will find that you need to swap out the carbs (ebay?) to attain the 100hp. Many outboard manufacturers design a motor around a certain displacement and then restrict the air or exhaust to market a lesser hp motor. The only difference I see with your motor is the carbs, changing the jets will only upset the fuel/air ratio. Don't just swap out the carbs without a tach as you may have to re-prop with the extra hp.

 

[connemaraisland]

Re: yamaha 80hp to 100hp by jet change

Not that easy - you would have to do a complete comparison to determine the differences and sometimes - there is no difference except the HP label is changed. Merc made the old tower of power straight six and in later versions there was no difference from the 80hp to the 115hp