Compression... How much do I need?

[puzzledprofessor]

I have a JW-10 that has 60 psi in one cylinder and 63 in the other. Is this old girl worth working on..... maybe if I replaced the rings?

Any information would be great.

Vance

 

[nwcove]

Re: Compression... How much do I need?

those numbers are good for a runner, could be better, but well worth bringing back to life.

 

[puzzledprofessor]

Re: Compression... How much do I need?

Thank you for the information, Nwcove. With the compression where it is should I replace the rings or is 60 enough?

 

[nwcove]

Re: Compression... How much do I need?

id keep it as is, do the ignition and carb, comp numbers are "ok", and may get better. (add some sea foam to your fuel for a slow decarb) but the motor should be a good runner as is.

 

[puzzledprofessor]

Re: Compression... How much do I need?

Great, I didn't really want to take it down that far anway. Thanks, again for the great info.

 

[kfa4303]

Re: Compression... How much do I need?

I agree. Anything over 60 psi should work. You might even see those numbers go up once the motor is warmed up and/or you've decarbed it with some Sea Foam, or similar product per the earlier post. You should be good to go now that the compression is ok. The carb and ignitions on these old motors are pretty cheap and easy to work on. Holler if you get stuck. Good luck.

 

[JB]

Re: Compression... How much do I need?

Misunderstanding compression readings causes many unneeded overhauls.

60PSI from a rope start 5.28ci engine is excellent compression; 5% difference is also excellent.

Don't fix what ain't broke and don't let others talk you into it.

 

[cajuncook1]

Re: Compression... How much do I need?

Please be very sure to use a fuel mix of 16:1. That is 8oz of TWC3 2 cycle marine oil mixed with 1 gallon of regular gas. Trying to go leaner will shorten its life. You can use a synthetic TWC-3 2 cycle marine oil, because it smokes a lot less.

Reliable, little motor you have there.

Here is a link that has a parts diagram and good little read. Please disregard his comment for 24:1 fuel ratio. Experts on the AOMCI forum are very convincing way the fuel oil ratio should stay 16:1

http://outboard-boat-motor-repair.c...rude Johnson 3 HP 1952-1954 Owners Manual.htm

 

[lindy46]

Re: Compression... How much do I need?

That compression is fine. Great little motors. I have the same motor in an Evinrude and she runs like new after a little maintenance/treaking, and will troll all day.

 

[puzzledprofessor]

Re: Compression... How much do I need?

Thanks to all for the great information and encouragement. I am looking forward to my new project.

Vance

 

[kfa4303]

Re: Compression... How much do I need?

This may help prof.


http://www.duckworksmagazine.com/07/columns/max/index1.htm