Change Carburetor for more HP?

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Ga Aquadog

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I have a 1999 9.9 hp Johnson outboard motor. Can I increase the horsepower to15 hp. By simple replacing the carburetor?
 

airshot

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I cant say on your particular model, however, I bought a new 9.9 back in 1994, itvwas a two stroke and a simple carb change could boost it to 15 hp. When I bought the motor the dealer also sold me the carb to make the change over. Had to wait one year until the new warranty was over to change it over. Made a noticible difference on my 14' tinnie. There are some models this works and other models where it doesnt work, not sure what years it works on other than the 94 models, but it needs to be a two stroke, doesnt work on four strokes so I am told....
 

cyclops2

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Not unless your present carb is defective.

There are several changes to convert fom 9.9 to 15 hp version. listed on web sites.
 

Ga Aquadog

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I cant say on your particular model, however, I bought a new 9.9 back in 1994, itvwas a two stroke and a simple carb change could boost it to 15 hp. When I bought the motor the dealer also sold me the carb to make the change over. Had to wait one year until the new warranty was over to change it over. Made a noticible difference on my 14' tinnie. There are some models this works and other models where it doesnt work, not sure what years it works on other than the 94 models, but it needs to be a two stroke, doesnt work on four strokes so I am told....
Thx. for the input. I will keep checking to see if my year motor is doable.
 

cyclops2

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Go to www.crowleymarine.com & look up the parts used in both a 9.9 and the 15 hp motors. They are a great supplier of all my Evinrude 2 stroke motors..
 

Ga Aquadog

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I appreciate the info. I have been looking for a place where Zi can order the right parts.
 

airshot

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I appreciate the info. I have been looking for a place where Zi can order the right parts.
New carbs are not cheap!! Back in 94 when I bought mine it was almost 300 bucks with the dealer discount !! Ouch..
 

fflegel

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I replaced the carb on my 2006 Merc 9.9 with a 15hp carb, didn't see a ton of difference in power, but it has never started or ran better than it does now.
 

Ga Aquadog

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New carbs are not cheap!! Back in 94 when I bought mine it was almost 300 bucks with the dealer discount !! Ouch..
WOW 😮 probably about my budget. I only gave $500 for the motor. It runs but a little underpowered for my boat
 
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Thx. for the input. I will keep checking to see if my year motor is doable.
That was the trick we used to beat the hp limit on private boats in lakes that were restricted to less than ten hp , We changed carbs from 9.9 to 15 hp model (1981 model Evinrude) no manifold change required! Kept the engine cover with the 9.9 showing! Had a buddy with an identical boat and 9.9 and I would outrun him all day long. Finally told him of the carb upgrade made the difference….presently doing a 20hp to 30hp carb and manifold swap on a Evinrude 1991 model.they run soooooo much better!
 

airshot

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See post #9

I wonder if the difference is just the jets. That would be a very cheap option. Likely $30.
Not jets...when I did mine back in 1994 the 15hp carb inlet was much larger in dia to allow more air. Don't recall the exact dimensions but the 9.9 carb which I still have was about an inch where the the 15 hp carb was about 1 3/8" in dia. Very noticible difference!!
 

wmk0002

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It's a great upgrade if you can find a reasonably priced carb. Take your time searching for one. It's tempting to snag one off ebay but in my experiences they are so overpriced there....prob because so many people fail to take care of their motors and think buying a $500 carb for their motor not worth too much more than that is the best route to take lol.
 
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