Top speed??

[saltchuckmatt]

I don't have the slightest clue.

Not perfect.

 

[ct1762@gmail.com]

Not perfect.

the 1983 15hp models are rated 6500-7000rpm. The 9.9's are something like 5500-6500 meaning you MUST be turning 6500rpm or so minimum to make 15hp with that tuned exhaust or you might as well be running a 9.9. I'd start with a 9'' or 10'' pitch prop. you could have a 12'' on there for all we know. a 15hp idles a little rougher and is no faster than a 9.9 until about 6000rpm! the 1993-newer big block motors are a different story.

 

[saltchuckmatt]

the 1983 15hp models are rated 6500-7000rpm. The 9.9's are something like 5500-6500 meaning you MUST be turning 6500rpm or so minimum to make 15hp with that tuned exhaust or you might as well be running a 9.9. I'd start with a 9'' or 10'' pitch prop. you could have a 12'' on there for all we know. a 15hp idles a little rougher and is no faster than a 9.9 until about 6000rpm! the 1993-newer big block motors are a different story.

Your confused, I'm not the poster....the not perfect line was about the not knowing if they had a life jacket.

 

[ct1762@gmail.com]

Your confused, I'm not the poster....the not perfect line was about the not knowing if they had a life jacket.

confused or just hit the wrong reply?

 

[saltchuckmatt]

Aye yai yai, this website is still not perfect!!!

 

[ct1762@gmail.com]

Aye yai yai, this website is still not perfect!!!

true

 

[Whoopbass]

the 1983 15hp models are rated 6500-7000rpm. The 9.9's are something like 5500-6500 meaning you MUST be turning 6500rpm or so minimum to make 15hp with that tuned exhaust or you might as well be running a 9.9. I'd start with a 9'' or 10'' pitch prop. you could have a 12'' on there for all we know. a 15hp idles a little rougher and is no faster than a 9.9 until about 6000rpm! the 1993-newer big block motors are a different story.

I thought the RPM max was 6K for these motors?
Anyway, a 15 HP motor will kick a 9.9 butt all day long. A 15hp has soo much more low end torque and throttle response then a 9.9 does. Top end they're only a few miles apart but it takes a bit of time for the 9.9 to max out, the 15 does it in seconds.
Did you check the throat of the carb? Maybe someone put a 9.9 carb on it.

 

[saltchuckmatt]

I thought the RPM max was 6K for these motors?
Anyway, a 15 HP motor will kick a 9.9 butt all day long. A 15hp has soo much more low end torque and throttle response then a 9.9 does. Top end they're only a few miles apart but it takes a bit of time for the 9.9 to max out, the 15 does it in seconds.
Did you check the throat of the carb? Maybe someone put a 9.9 carb on it.

Well said....or a 15 cap on it.....smaller restricted plate, bad fuel, coil cutting out at high power, kill switch slightly killing it at high speeds or a tiny tiny speck of sand in the main jet.

 

[flyingscott]

I thought the RPM max was 6K for these motors?
Anyway, a 15 HP motor will kick a 9.9 butt all day long. A 15hp has soo much more low end torque and throttle response then a 9.9 does. Top end they're only a few miles apart but it takes a bit of time for the 9.9 to max out, the 15 does it in seconds.
Did you check the throat of the carb? Maybe someone put a 9.9 carb on it.

Thats not true. A 9.9 performs much better at low RPM. The 15 is only marginally faster after 5500 rpm

 

[Whoopbass]

About 10-15 years ago I had a 9.9 carb and a 15hp carb and water tested them on the same boat/motor within minutes apart. The motor was probably a mid 80's JohnnyRude that came from the factory as a 9.9. When the 15 hp carb was on the performance was night and day. The 9.9 was a dog. No I did not go trolling. The test was just get up and go and when in mid range hit the throttle and get up to WOT.
If a guy wants a good hole shot or has a heavy boat or load the 15hp is the way to go.