76' John 15 77' evienrude9.9 questions

I have had an evienrude 9.9 (e10rcse) on my boat for about a year. i was given a 15 seahorse (15rl76a) not running (yet) with a busted lowerend.

the motors look exactly the same other then paint.

1) how can the johnson push out 50% more power with the same "block"?
2) can the lowerunits be swapped?
3) can i install the alternator from the 10 horse to the 15?

thanks -MD

Re: 76' John 15 77' evienrude9.9 questions

Looking at the model number for the Evinrude, I would say its a 1980, not a 1977. HP difference on powerheads of the same displacement can be attributed to a number of factors such as carb jetting and or different carb all together ignition timing, rating the HP at different RPMs etc. I dont know this the be the honest to god truth but Ive been told by many people that most 9.9s are under rated in terms of HP, they just market them as 9.9s because 9.9s are the motor of choice for folks that want the most power they can get without having to licence their vessel.
So if this is true and you take that into consideration, the actual net difference may be only 2 or 3 HP.
If I'm out to lunch on this theory, someone chime in and let me know.

Re: 76' John 15 77' evienrude9.9 questions

The 9.9 is a "choked" down 15HP done by putting a smaller bore carb on it. Another forum member "scanman" upgraded his 9.9 to a15 by changing the carbs and wound up with a screaming engine.

Don't know the answer to the other questions but somebody on here does and will probably chime in. Good luck

Re: 76' John 15 77' evienrude9.9 questions

MaddysDaddy said:

I have had an evienrude 9.9 (e10rcse) on my boat for about a year. i was given a 15 seahorse (15rl76a) not running (yet) with a busted lowerend.

the motors look exactly the same other then paint.

1) how can the johnson push out 50% more power with the same "block"?
2) can the lowerunits be swapped?
3) can i install the alternator from the 10 horse to the 15?

thanks -MD

Click to expand...

1) I don't know but it has to do with the carb. bore size and in some models a tuned exhaust.
2) I don't know of any reason they can't. Give it a try it won't take more than an hour and then you will know for sure.
3) I doubt it. I believe (correct me if I'm wrong) your 76 will have the old points/condenser ignition while the 80 will have CDI electronic ignition. That is the reason I doubt you could do it.

Here is a link I think is a must read for us 9.9 and 15 owners. Leeroy may well have the answers to your questions in his articles. Best of luck. Rick.
http://www.sschapterpsa.com/ramblings/Ramblings.html