1972 9.5hp to 15hp?

[GreenF350]

Ok...Don't flame me off of the forum for this.
My dad has a 1972 9.5hp Evinrude that he has had forever and is VERY well taken care of. Runs like a champ, planes out his 14ft Vhull aluminum boat but will also troll out in lake michigan for Salmon, etc. He has been talking lately about how everyone says the 9.5 and 15hp are pretty much the same motors and he may try and convert his over to the 15hp. He has done all of the work on this motor since I can remember and I am 27 so I think he can pull it off, if it can be done.

So, can it be done? If so, I would like to help him out and save some hassles along the way, so what parts would one need to do this. Here is what we are currently thinking....
Flywheel
Carbs (or a rejet at a minimum)
I know there had to be other things different, but I am just not that familiar with outboards. I know with dirtbike 2 strokes that the reed valves can make a pretty big difference, what else?

It's winter and we got to talking, so I said I would post up on here and see what I could find out. You gotta love the internet. Thanks for what information you can add to the discussion.
-Aaron

 

[Frank Acampora]

Re: 1972 9.5hp to 15hp?

It ain't all that simple. Things ain't always what they seem to be.

Frequently the engines share the same block but have a different bore and stroke. Sometimes the lower unit gear ratio is also different.

Not saying it can't be done, just that it may not be easy and you still may not get the 15 hp you are looking for. You will need to do a LOT of investigating. LOOK BEFORE YOU LEAP!

Repost on the Evinrude/Johnson forum. I'll bet there are fellows there who know the engine like the backs of their hands.

 

[GreenF350]

Re: 1972 9.5hp to 15hp?

I knew it couldn't be TOO simple or everyone would have bought the 9.5hp and upgraded. Just wondering if it was doable, and what it would take. I guess I could go post up in there...I just didn't figure this was really a repair question. Thanks.
-Aaron

 

[tashasdaddy]

Re: 1972 9.5hp to 15hp?

if you want a 15, better of selling the 9.5 and buying a 15.

 

[JB]

Re: 1972 9.5hp to 15hp?

The 9.5 and the 15 are NOT similar. It is the 9.9 and the 15 that seem similar, but the cost to convert is prohibitive and not worth the trouble.

Keep the 9.5 and leave it alone or swap it for a 15.

 

[Solittle]

Re: 1972 9.5hp to 15hp?

Seems I remember that you could kick some years but not others of the 9.9s to a 15 rather easily by changing the carb.

 

[wbeaton]

Re: 1972 9.5hp to 15hp?

Seems I remember that you could kick some years but not others of the 9.9s to a 15 rather easily by changing the carb.

I think there was a narrow window in the 1970's where that was true. However, I believe it was also said that those 15 hp motors output closer to 13 hp and wasn't as noticeable after the upgrade as one might want or expect.

 

[JB]

Re: 1972 9.5hp to 15hp?

He doesn't have a 9.9. He has a 9.5. Whole different animal.

 

[Chinewalker]

Re: 1972 9.5hp to 15hp?

JB's right. The 9.5 is sometimes referred to as the Mushroom Motor, or Lowboy, at least in polite conversation. Nice enough motors, but they were maxxed out at 9.5 horses. 1974 saw the debut of the 9.9/15 horse series - completely different design... Built them well into the 1990s...
- Scott

 

[GreenF350]

Re: 1972 9.5hp to 15hp?

Ok...Sounds like a no-go then. I knew it might take some work and money, but it looks like it isn't even possible. Thanks for all the info guys.
-Aaron