1977 9.9hp converting to a 15hp...

[dfrants]

what all is needed to convert a 1977 9.9 Johnson to a 15hp? Didn't they make a kit at one time? is it something a shade tree mechanic can do?

 

[flyingscott]

Carb only in 1977

 

[jimmbo]

This topic comes up on a regular basis. There is no kit to convert. One just buy the parts they need. What is required, differs depending on the year. Some are just a carb change, others require also require an exhaust tuner change, or a different intake/reed assembly. Can another 1000 rpm really result in a 50% increase in HP?

 

[oldboat1]

...and might already have the larger carb (throat size and h.s. jet): http://www.leeroysramblings.com/Johnson 9.9_15.htm

 

[flyingscott]

If you have a 1977 9.9 you do not have the bigger carb.

 

[oldboat1]

...but always prior shadetree mechanics. Can look into the throat to check the size (LeeRoy's site has a good side by side of the 9.9 and 15).

 

[dfrants]

Found the bigger carb and prop for $20. As a 9.9 she went 19-20mph, now as a 15 she does 22-23mph. and idles just as well.