Johnson 9.9 HP Change to 15 HP "HELP"

[JarHead-8]

I have a 9.9 HP Johnson, aprox 1989 Model and I have been told that all I need to do is to change the jets in the Carberator and WHAM-O I have 15 HP. I thought I better check with the pros before I get my self in a heap of trouble. Thanks, I need advise and direction, can this be done.<br />JarHead-8

 

[jonesw]

Re: Johnson 9.9 HP Change to 15 HP "HELP"

I'm no pro (maybe Prp Am), but if that's the only thing you do, I would guess the only thing you would get is a poorly mixtured 9.9. Jetting alone will only directly affect mixture, it's usually done with other mods that let the "breath" more without which the modified engine would now be too lean.<br /><br />Please verify this and correct me if you find out different.

 

[JB]

Re: Johnson 9.9 HP Change to 15 HP "HELP"

JonesW is correct. <br /><br />There are many (expensive) differences.<br /><br />Changing jets would only give you a lousy running 9.9.<br /><br />

 

[the machinist]

Re: Johnson 9.9 HP Change to 15 HP "HELP"

A larger mainjet will just flood you out & the engine will blubber at high speed, you need a larger throated carb also to mix the larger quantity of fuel.<br /> Take a look at this website article<br /><br /> http://www.pugetsoundanglers.org/Fishing Info/Johnson 9.9_15.htm <br /><br />It gives the info you may need.

 

[MGuckin]

Re: Johnson 9.9 HP Change to 15 HP "HELP"

Good article