84 Johnson 20hp Mod

[NeanderBob]

I have an 84 Johnson 20hp, my father-in-law says this basic motor was sold in different states of tune from 20hp-35hp. It does look large and is very heavy for it's hp rating. Is there a cheap way to uncork this motor to make it produce it's top hp rating? It seems a waste to haul around a heavy, detuned motor.

Thanks for reading.

 

[tashasdaddy]

Re: 84 Johnson 20hp Mod

it is possible, but cost prohibitive. if you want more, sell it and buy what you want.

 

[NeanderBob]

Re: 84 Johnson 20hp Mod

Thank-you, good advice.

 

[kynolan2183]

Re: 84 Johnson 20hp Mod

It depends on the state you are in and wether or not you boat on federal waters.
For a 30 hp follow this:
It is a cheap mod. 30 hp carb on ebay 27 dollars rebuild kit for carb 16
Remove the carb and restrictor plate. Make the hole on the restrictor plate bigger via drimmel tool ect.

Make sure to remove the plate and do this away from the motor as little metal shavings are very bad for the motor.

Clean the plate. Clean it again. Put it on the dish washer. Clean it again.
I can't state enough clean it again. Clean your hands.

Put it back together with the mod plat and the 30 hp carb.

Get a new prop with 2 more inches of pitch. You will need it. to keep the RPMs with in WOT.

Put an oh SH** handle in your 1436 you will need it.
Sounds like I have done this before YES would I do it again YES.

For a 25 hp follow this:

Take off the carb and restrictor plate. Follow all of the cleaning above.
Bore the restrictor plate out to bigger. Put back 20 hp carb.

History:
Before the new BRP web site you could look up all of the part numbers.
The 20 and 25 catbs are the same the restrictor plate was different.

The 30 hp carb was for the 30

The 35 hp carb was for the 35

all had different plates.

I did this on my 84 evinrude on a 1984 wide mouth 1436 monark. went from low 20 ish to low 30 ish mph at 6180 rpm on 15 pitch. I was a fun ride. Running on the lake it was always great to find glassy water and see peoples looks when I went flying by.

Also I took a 1000 dollar boat ran it for 4 years and resold it for 1700 because of the mod.

The johnson can handle it.

The big difference was went I had my 285 pound buddy sitting up front.

 

[bgbass.1]

Re: 84 Johnson 20hp Mod

have the same motor all i did was put a 30 hp intake and carb. on cost about 350 runs like a scalded bear now.