G'day i was wondering if there is any difference between 9.9 and 15 hp for 1975 as my old johnson isn't puting out as much power as it used to and i think i know where i can get a cheap carbie. is there any side affects of this? <br /><br />Thanks
Have you tried a good tune up....top to bottom...lately? RPM's down? You really won't see that much difference with the 75' in changing out the carb to a 15.<br /><br />Run a compression test. See how wore out the old girl is and go from there. If the compression is in the 90's, even the upper 80's, and even, give her a tune up including a decarb. It'll make a difference.
Howdy, Freak.<br /><br />You would probably be better off to make sure your 9.9 is in top shape. The only real change you would notice with a 15HP carb is a lighter wallet.<br /><br />I would start with a compression test and follow up with a clean carb and a careful link 'n' synch.<br /><br />If she hasn't been decarbonized in a while I would do that, too.<br /><br />Good luck.
From my own experience the larger throat 15 carb will give you a little more power but will use a lot more gas. The best thing to check for is that you are not running a worn out prop. A full sized prop on this motor will amaze you with the change.
I agree with the others check eveything over from top to bottom. If the engine is in good shape and still seems to be holding its own then just clean the carb and do a tune up, points, condenser, pulgs etc...
One thing I forgot to add if the old engine is losing power then there must be a problem. Instead of skipping over the problem fix that before you decide to modify things, this will only add to the problem down the road
If you can get that whole 15 cheap, give it a try. It never hurts to have a parts motor. But promise me something. Don't do it to get around lake limits or boat capacity, and always represent it's horsepower accurately. But regardless, you won't hardly notice any gain.
G'day the engineis in tip top condition it is just plain worn out. the pistons have plenty of slop side to side and you can push the flywheel side with plenty of slop. But if the carbie just uses more fuel im probably better of not worrying about it<br /><br />Thanks for the Posts
Probably a good decision OMC.....<br /><br />To JB.....no problem partner.....always good to get a second opinion.....even if it's the same as the first....
