Compression?????

[shooter26]

Hello,<br />Before I spend $30.00 on a manual which I will do anyway, could someone tell me what the correct compression should be on a 1964 9.5hp Johnson M# MQ-10R. <br />Thank You,<br />Jay

 

[clanton]

Re: Compression?????

It may not be in the manual. I think it would run with about 70 lbs.

 

[Boatist]

Re: Compression?????

Do not know but my 1975 15 HP Johnson is 115 and 120 and it has lots of hour on it. My factory manual does not have a range.

 

[shooter26]

Re: Compression?????

Thanks for the reply Clanton and Boatist,I checked cold.. compression 55 out of top 50 bottom. Hot.. compression 30 out of top 25 out of bottom. The tester I used is a rubber tip type (push in and hold). It's also pretty old, could these numbers be right or should I try a screw in type compression tester. <br />Thanks Again,<br />Jay

 

[Bob_VT]

Re: Compression?????

A motor will run on low compression. Considering the age of the motor, you may be carboned up a bit which is preventing the rings from sealing completely. On the other hand the rings may be worn too.<br /><br />Bob

 

[Terry H]

Re: Compression?????

I would surely test it with a good screw-in guage before making any decisions...stop by a good auto shop and have them check it for you. Most importantly...does it run, and why do you need to know the compression...just a Thought

 

[revertmastec]

Re: Compression?????

Thought,<br /><br /> Shooter has water coming out of his sparkplug so he was checking to see if the head gasket might be cracked. Shooter try and stick with your original post it makes it easier for everyone to follow your progress and help you.

 

[shooter26]

Re: Compression?????

Thanks for the replys, Sorry about the confusion Thought101 and Revertmastec I have (2) motors Iam posting about. A 25hp Johnson with water leaking out threads of top sparkplug which I'll be able to work on all of next week. The other is a 1964 9.5 MQ-10R Johnson Iam trying to fix for my father in law, I suspect a fuel problem it runs good in a tank in the start position but when I turn it down to idle it starts to spit cough sneeze? what ever you want to call it and then shut off. I can start it again in the start position and run forever just not in idle, seems like it's running out of gas? Any ideas? Again sorry about the confusion.<br />without all your help I would be lost for sure. I enjoy working on outboards and the only way Iam able to do this is by learning from other post and questions on this form. <br />Thank You, <br />Jay

 

[clanton]

Re: Compression?????

The hot numbers are low, sneeze is lean. I would do a decarb, clean carb. If this has the sparkplug wires that route under the flywheel, they get old and the wire breaks inside the outer core, and when you move the throttle, which moves the timing plate the engine will stall.

 

[Boatist]

Re: Compression?????

Shotter26<br />I think you compression is very low. My 1976 15HP Johnson cold was 120 top 115 bottom, after decarb/engine tuner thing hot is top 127 bottom 120 and this engine has lots of hours on it. I also used the push in type compression tester but had my son pull rope. I suspect your ring may be warn allowing too much blow-by. Try squirting 30 weight oil into each cylinder and check compression again. If compression come way up I would think about replacing rings. If get no change then I am not sure. The engine tunner/decarb stuff I just did on my engine and it does start easier and it made a big difference as to where I set low speed jet for it to run best. Hope you find a easy cheap fix. Make sure to report back outcome.