what is the difference between blocks

[blgrams]

After rebuilding my 40 HP 1991 johnson I could only find 3 differences between the 40 and 50 HP other than options. the reed blocks, the orifices in the carbs. and the block/crankcase. Is there any difference except more threaded holes for options on the 50HP?<br /><br />Bruce

 

[McGR]

Re: what is the difference between blocks

The porting witin the block for the transfer of fuel/exhaust will be somewhat different in the 50hp block. This is the primary reason they have different p/n s. This porting works in conjucntion with the carb and reed differences to move more air/fuel through the motor resultin in more h.p. I once had an '89 40hp and was given 55hp carbs to put on it in hopes of performance gains... it didn't work. Idle was fine, but it fell on its face when you tried to accelerate.

 

[jimmbo]

Re: what is the difference between blocks

Porting differences on a 2 stroke block are like different camshafts on a 4 stroke, they determine the RPM range where the engine produces peak torque and power.

 

[blgrams]

Re: what is the difference between blocks

Thanks, the only number I could find on the used block is on the "quarter" and on my old block it matches the serial number on the tag on the outside of the motor. Is there any way to tell if the used block is a 40 or 50?<br /><br />Bruce