I had a late 70's 9.9 that I changed to a 15 and in addition to a different carb, there was also a spacer that allowed the reed valves to open more. It was a great running motor until I let a friend drive the boat. He made a sharp turn at high speed and the motor tore off of the transom and went to the bottom of the creek. It's still there if anybody wants it!
Did you swap out the prop as well to account for the extra horsepower? I’m thinking that a 33% increase in horsepower would require more pitch at the same RPM.
i have a 1998 johnson 9.9 and 15hp models. Both vary low hour motors. they both will idle down to almost nothing. the 15 screams top end but seems to stumble mid range were the 9.9 remains smooth. i think the cylinder porting are different between the two. maybe thats why i only see 9.9's on sailboats
That's one way to make your johnson bigger😊
I had a late 70's 9.9 that I changed to a 15 and in addition to a different carb, there was also a spacer that allowed the reed valves to open more. It was a great running motor until I let a friend drive the boat. He made a sharp turn at high speed and the motor tore off of the transom and went to the bottom of the creek. It's still there if anybody wants it!
bet
I would love to have this motor. These gems are tough to come by.
same
Did you swap out the prop as well to account for the extra horsepower? I’m thinking that a 33% increase in horsepower would require more pitch at the same RPM.
i have a 1998 johnson 9.9 and 15hp models. Both vary low hour motors. they both will idle down to almost nothing. the 15 screams top end but seems to stumble mid range were the 9.9 remains smooth. i think the cylinder porting are different between the two. maybe thats why i only see 9.9's on sailboats
What's next? Cut the cylinder to set squish and some porting? 😂
You have also change to the turned exhaust tube that 15hp has. If you put more gas in you have to gas more exhaust out also to be 15hp
What does the knob on the handle , I try to play with mine but don't see waht it does??
Thanks, and good video
what fuel mixture for this engine is 1:100 or 1:50
Kinda surprised me how well that thing moves for such a small motor
That's about right. My Evenrude went from
9.9 hp 30 kph
15 hp 35 kph.
My 15hp Nissan goes 40 kph
Where did you find a carb I have same year motor I’d love to do the swap but can’t find a carb
Yea where can we get the carb from?
Ill it troll as nice with the larger carburetor?
no definitely not!
i was told you can do the same with a mercury .