1965 Johnson 9.5 compression

[jeradlk]

I recently bought a 1965 Johnson 9.5. I changed lower unit oil and have started it and it pumps water fine. I decided to do a compression test and only got 60. Both cylinders measured at 60. I ran the motor for a while longer and there was not change. Any thoughts what the problem might be or is it allright as long as both cylinders are the same.

 

[DJ]

Re: 1965 Johnson 9.5 compression

That' about right. The important thing is they are the same.

 

[Walker]

Re: 1965 Johnson 9.5 compression

Pull start motor right??<br />If you can start it will a pull start then it has plenty of compression.

 

[stl]

Re: 1965 Johnson 9.5 compression

That is very interesting I bought the same motor last fall. I almost didn't buy it because it only had 85 on both. I had read it should be around 100. I decided to buy it anyway. I think it is more important to have the same psi on both. But I am no expert. The motor has been great so far. I have since read tons of posts on here about the 9.5's and the exhaust gasket leak. If I had known about that problem I probably would have stayed away from it. Ill just keep my fingers crossed.

 

[jeradlk]

Re: 1965 Johnson 9.5 compression

Yes it is a pull start. Thanks for the replies. Just trying to decide if it should be rebuilt.

 

[CFronzek]

Re: 1965 Johnson 9.5 compression

If the cylinder pressures are only 60lb. you may as well rebuild it. <br />Even if you can get it to start it is at the extreme limit and is only going to get worse with use. Somewhere between 50-60 pounds these motors get to the point where there isn't enough pressure to get them to light off. Also, low cylinder pressures indicate that a lot of pressure is getting past the piston rings. When you run a two-stroke motor with bad rings combustion gases get into the incoming charge and lean the mixture severely. It can make the motor heat up badly and even burn pistons. And, of course, your HP will be way down. <br />If you decide to use this motor, as is, be sure to take your oars.

 

[P51D]

Re: 1965 Johnson 9.5 compression

I've got a 1973 9.5 HP with about 65 psi on both. It runs very well and develops rated rpm. I've seen a lot of "low" compression readings for the 9.5 in this forum, accompanied by "runs well" comments. I'm starting to thinks it's nature of the beast.

 

[jeradlk]

Re: 1965 Johnson 9.5 compression

I think I will rebuild, at least replace the piston rings. Does anyone know where you can get piston rings the 1965 9.5 I looked on this web site and several others and can't seem to find anyone that carrys them.

 

[jeradlk]

Re: 1965 Johnson 9.5 compression

I think I will rebuild, at least replace the piston rings. Does anyone know where you can get piston rings the 1965 9.5 I looked on this web site and several others and can't seem to find anyone that carrys them.

 

[P51D]

Re: 1965 Johnson 9.5 compression

Jeradlk - IF you DO decide to rebuild, please post the before & after results. I'm curious to see how much the compression improves. Also, have you run the engine on a boat yet? I'd also like to hear how much on-the-water performance improves.<br /><br />THANKS and good luck.

 

[cbotzum]

Re: 1965 Johnson 9.5 compression

I look forward to the results as well. I checked mine yesterday...63 per. I'm having to run rich for semi-smooth operation. I'm refurbishing a second motor, but yet to receive the parts.

 

[jeradlk]

Re: 1965 Johnson 9.5 compression

Well I took the head cover off and the head gasket looked blown. Checked out the pistons and cylinder walls why I had it apart and they looked good to me, no scuffs or pits. I ordered a new head gasket and replaced it but unfortunately no improvement in the compression. Any ideas what else it might be. I though it might be piston rings but with both cylinders reading around 60 it seems like it might be something else, maybe an exhaust gasket. Any ideas?