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Old 14-06-2014, 09:34   #1
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Johnson 9.9 and 15hp Motors

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
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Old 14-06-2014, 09:43   #2
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Re: Johnson 9.9 and 15hp Motors

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....
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Old 14-06-2014, 09:44   #3
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Re: Johnson 9.9 and 15hp Motors

here you go.
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Old 14-06-2014, 09:44   #4
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Re: Johnson 9.9 and 15hp Motors

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.
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Old 14-06-2014, 09:56   #5
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Re: Johnson 9.9 and 15hp Motors

Quote:
Originally Posted by CaptForce View Post
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.
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Old 14-06-2014, 10:02   #6
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Re: Johnson 9.9 and 15hp Motors

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.
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Old 14-06-2014, 10:19   #7
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Re: Johnson 9.9 and 15hp Motors

A number of 9.9 hp outboards are de-tuned 15 hp models.
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Old 14-06-2014, 10:43   #8
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Re: Johnson 9.9 and 15hp Motors

thanks for the quick replies,
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Old 14-06-2014, 10:49   #9
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Re: Johnson 9.9 and 15hp Motors

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
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Old 14-06-2014, 11:05   #10
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Re: Johnson 9.9 and 15hp Motors

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