1981 Johnnyrude 90-115-140 differences only carburetors?

[bkupmstr]

From the looks of the srvice manual, the only differences between the 3 engines is just the carburetor jets?
can I just re-jet my 115 carbs to become a 140?

 

[racerone]

NO, No ------------the 90 HP block has smaller intake ports.-----------------The 115 HP has the bigger ports --------------------The 140 HP has the extra bits , tuned exhaust hence the bubble on the back.

 

[joereeves]

Changing to larger (fuel) high speed jets will just load the engine up with fuel, like engaging a choke.

Changing to larger (air) slow speed jets will cause the engine to run lean = improper lubrication etc.

Solution = let it be.