Johnson 9.9 and 15hp Motors

[jplowing]

I have a customer who just bought a small lund fishing boat and the guy that sold it to him said something I never heard before,he said that some of the 9.9 motors were upgraded to 15hp powerheads by changing the powerehead and carb,now the cover says 9.9 and I ran the model# and it comes up as a 1974 9.9 Johnson,is there any truth to this story, and when you look at these motors how can you tell a 15hp from a 9.9hp,thanks,JRD

[nmuir]

I heard that it was just the carb that made the difference (ie not even the powerhead), but cannot remember where I heard that - it was a while ago. I have a mid 90's 15....

[Vasco]

here you go.

https://www.youtube.com/watch?v=V7rP8oOcAVQ

[Hudson Force]

I could be wrong, but my understanding is this. Possibly Johnson and I believe Yamaha produce outboard motors that comply with regulations not allowing outboards of 10hp or more in environmentally restricted waterways. This is achieved by altering their 15hp motors with a carburetion system that reduces their horsepower to 9.9 . I have known people with 9.9hp Yamahas and they have increased the horsepower by changing the carburetors.

[fstbttms]

Originally Posted by CaptForce

I could be wrong, but my understanding is this. Possibly Johnson and I believe Yamaha produce outboard motors that comply with regulations not allowing outboards of 10hp or more in environmentally restricted waterways.

The reasoning is that a 16' (or longer) boat with a 10hp motor (and above) must be registered with the DMV. The same boat with a 9.9 hp does not.

[transmitterdan]

In addition, many small lakes in the US have a 10HP maximum allowed by local or federal regulation. Thus 9.9 is very popular on these lakes.

[Terra Nova]

A number of 9.9 hp outboards are de-tuned 15 hp models.

[jplowing]

thanks for the quick replies,

[jplowing]

so for us to know for shure I would have to compare carb venturi size with a known 9.9 and check for the exhaust tube, and also top end speed would help,thanks

[Vasco]

In Canada you don't need to license a boat under 10 hp. Hence the 9.9.