Head Check

[alumistar]

I wonder if one can shave the head on a '65 9.5hp 2-stroke evinrude a bit for a tad more horsepower?

 

[R.Johnson]

Re: Head Check

On a 9.5 maybe a tad more! there again! maybe a tad less. On these little engines, all you may notice is the reliability. These engines were mean't to be compact fishing motors. That is all they are.

 

[Forkin' Crazy]

Re: Head Check

Don't do it. A tank of bad gas and you'll smoke a piston. It would probably be best to run a min of 93 in it anyway.<br /><br />If you want to go faster, get a newer 9.9, I like '77 to mid 80's and put a 15hp carb on it. It's a way better engine.

 

[alumistar]

Re: Head Check

Forkin' Crazy....I found an '82 9.9. So, what happens if I put the 15hp. carb on it?

 

[DMR Mechanic]

Re: Head Check

The 9.9hp and 15hp motors are the same. Put the 15hp carb on the 9.9hp and you now have a 15hp motor.

 

[alumistar]

Re: Head Check

Thanks to all for the help...

 

[ledgefinder]

Re: Head Check

screamandfly.com has a pretty good tech forum on modifying outboards. No doubt you absolutely are pushing it to shave heads, advance timing, raise ports, relieve exhaust, etc., but it is fun if you have a spare powerhead hanging around. I've been pondering the same thing with some spare 9.5 parts myself. Getting the boat setup right (prop selection, raise the motor until you lose water pressure, etc.) makes a big diff if you haven't done that yet.

 

[alumistar]

Re: Head Check

ledgefinder, still haven't tried a different prop. sea-level oem prop is still the one on shaft. thing is, I'm a beefy guy(280lbs) can't quite get it on plane man(1972 12ft. Starcraft)<br />I suppose the altitude is really screwing with my power levels!

 

[ledgefinder]

Re: Head Check

I forgot you're the guy at high altitude. You probably could mill the head (I'm sure I'll get some protests from other list members) if you're running above 5000 ft. The compression isn't all that high on the 9.5s anyway. You could get a spare and try it on that one (easy does it). I can calculate approx how much to mill to compensate for the lower air pressure - what altitude are you typically running at? <br /><br />That said, I'm still curious whether or not your linkages are OK. Have you checked whether your max timing advance is correct? Should be able to visually tell whether you're getting WOT at the carb. <br /><br />If you've already got a 9.9 lined up, might be the way to go right there - I'm just surprised that 9.5 won't do it. I've run a newish Mariner 9.9 (after the 1986 re-rate) that was plenty of motor on a 14' aluminum deepV, at least for one occupant in the ocean.<br /><br />BTW, my brother got married at one of those 10th Mtn huts above Leadville. I can tell you I didn't move that fast at that altitude either.

 

[Solittle]

Re: Head Check

alumistar - You need to get some weight forward even if it is just ballast. I run a 1975 9.9hp (long shaft even!!) on a 12'er and it will get the wife & I up on a plane & our combined weight is quite a bit over 280. When I am alone (200lbs) I can get up on a plane but it takes forever as the nose is very high (due to all the weight at the transom)& it takes a while to get on the step.

 

[alumistar]

Re: Head Check

thanks for the help,<br />ledgefinder, I run anywhere between 4000ft, and roughly 10500ft. depends on the week and whether I'm going for walleye, trout, kokanee, or bass. hey, when you got that kind of variety mixed in with beautiful surroundings why not travel around a bit.(unless you purposely fish at Gondo, WY, not saying WY is bad, just desolate and boring )<br />solittle, I'm thinking of going the 15hp route due to the choke factor above 4500ft. and, I can build a custo console with remote controls to allow me to sit in the middle of the boat, which would take care of everything. hmmmm....don't sound to bad