1965 Johnson 9.5 will not run WOT

My 1965 Johnson 9.5 hp will start easy, and seems to run good at WOT for 10 to 15 minutes and then slowly starts to slow down. From then on it will not run at WOT; seems to be at about 2/3 to 3/4 open even with WOT. Also, it does not want to idle very good either. Any suggestions?

Re: 1965 Johnson 9.5 will not run WOT

The first thing I would check is your fuel tank. Make sure that it's venting right. A tank that's not venting will create the symptoms you described. Check the fuel line for cracks and loose clamps. If your tank is venting, try pumping the primer bulb when the motor starts slowing down.

Re: 1965 Johnson 9.5 will not run WOT

Thanks Oldcatamount...I'll certainly try your suggestion. Thanks!

Re: 1965 Johnson 9.5 will not run WOT

There are quite a few possibilities. When you say it doesn't idle very well, does it miss? When running at wot for a while does it miss? Some things to try, especially if you haven't already done so on this motor.
- Carb rebuild (very easy parts are less than $30)
- Clean fuel filter
- Switch to plastic fuel tank (mine was flaking choking the fuel)
- New points/Condensers (fairly easy parts about $30)
- New fuel lines
Sounds like a lot, but on a 45 year old motor....stuff starts to break down
I got fantastic advice on here when refreshing my Sportwin, and am glad I spent the time and effort to replace all the 'wearing' parts. I think I spent close to $200 but now have a very reliable motor that I understand the workings of.
p.s. If you're going to the trouble, I'd suggest a new water pump impeller also