Approx 1966 Evinrude Sportwin 9.5hp power issues

[eryck65]

I will verify the year and HP when I get home tonight, but last yeat when running the motor for the first time ( a hand me down from Dad ) I noticed the motor did not have the power to plane a 12' aluminum boat with just me in it. I had just had the motor tuned up, purchased a couple universal gas tanks at Walmart with OMC fittings, dropped int he appropriate oil and 5 gallons of 87 octane unleaded gas into the tanks and drove up to Canada. My Father was there with a 9.9 Suzuki and literally could drive circles around me. The boats were identical in length with little beam difference, Any ideas what might have caused the lack of power? Was it the unleaded fuel or do I have deeper issues.<br /><br />Thanks<br />Eric

 

[JB]

Re: Approx 1966 Evinrude Sportwin 9.5hp power issues

You have deeper issues, Eric. We need something more concrete to go on, though. The difference between 9.5 and 9.9 shouldn't be much at all.<br /><br />Do a compression check on your engine. You should get 90lb. or more on both, and less than 15lb. difference between the two cylinders.<br /><br />Inspect your spark plugs after running at 3/4 WOT for a while. They should be grey to tan, and not wet.<br /><br />Let us know what you find.<br /><br />Red sky at night. . . <br />JB

 

[BayStLouis]

Re: Approx 1966 Evinrude Sportwin 9.5hp power issues

Eric:<br /><br />I've got a '65 Sportwin - it will most definitely plane a 12' boat with two people. In addition to checking the compression, you might want to check to see if the exhaust ports are partially clogged with carbon build-up. That's a very common cause of low power output in 2-stroke engines. Get a service manual off of eBay - look for 1964-1973 Evinrude/Johnson 9.5. Not much changed over those nine years, so if you can't find a '66 manual, another year will suffice.<br /><br />BSL

 

[jimdi]

Re: Approx 1966 Evinrude Sportwin 9.5hp power issues

I had this same engine on my dads boat for over 30 years - could Plane 4 people in a 14' lowe line with no problem.<br /><br />Great engine - Only once needed a carb rebuild and maybe a new spark plug here and there. <br /><br />jim