65 sportwin octane limit

[alumistar]

i have a 65 9.5hp evinrude. i am the high altitude guy, i need to know how high of an octane rating i can introduce to my motor. i have the option of these: 87,89,91,94pro,96highpro,98streetperf.,<br />100dragfuel,100purple avgas,101hybrid race,and<br />104(the red juice) i can get all said products in denver for less than $4.00/gal. <br />i run J7C champion plugs--100/98psi.compression---brand new ignition system, carb.rebuild, fuel pump, water pump, in-line spectre clear fuel filter, and head gasket--<br />also, i run(at different altitudes),3different props<br />8 x 7<br />8-1/8x8<br />8-1/4x8-1/2 <br />i sure could use some advise for the health and maintainance and, of course, higher power out put.<br />thanks to all with advise

 

[JB]

Re: 65 sportwin octane limit

Howdy, Star.<br /><br />That 9.5 will run just fine on any gas over 80 octane. If you run over 87 octane you are wasting your bux.<br /><br />Good luck.

 

[alumistar]

Re: 65 sportwin octane limit

JB, are you sure a higher octane won't increase any performance factors, including gph?

 

[DJ]

Re: 65 sportwin octane limit

Absolutely positive octane won't increase performance. The engine only requires more than 80. 87 is your best bet. Anything over that just makes for a slower combustion rate and leads to deposits.

 

[alumistar]

Re: 65 sportwin octane limit

then 87 it is. what about spark plugs? i've been told that i can use any heat range in the JC series plug from J4C,5C,6C,7C and J8C at this altitude, with O2 loss, how hot should i go?

 

[DJ]

Re: 65 sportwin octane limit

alumistar,<br /><br />Run as cool a plug as you can, without fouling.<br /><br />J4C, J6C

 

[DJ]

Re: 65 sportwin octane limit

alumistar,<br /><br />Do you have this thing jetted for your altitude? If not, see your John/Rude dealer for an altitude/jet chart.

 

[alumistar]

Re: 65 sportwin octane limit

Yeah DJ, it's jetted for 4000-6000ft. I change jets when I know that I'll be above 8500ft. And I have a set for 1000-2000ft for when I get to go on vacation to Lake Sakakawea, ND. Except I've been told a few times that the hotter the plug the bigger the fire. So what should I do?