compression

[jcjoyner]

Me again, now that I have the firing order for my chrysler 120 model 120 HC, I would like to know if the compression readings I got are ok I'm going to check them again with a screw in guage. I got a 100 in each cylinder this is with a rubber tipped hold it in the hole guage. Any help is appreciated thank you. newbie but I really like this forum, from what I can see so far there is a lot of knowledge to be found here.

 

[JB]

Re: compression

All cylinders within a 10% window is a good result, jcj. Don't get psi paranoia; Gauges, conditions and technique vary too much to say "at least Xpsi".

 

[jcjoyner]

Re: compression

thanks appreciate the input. I wasnt really paranoid but most engines(car) are higher. again this is a smaller engine. true they are pretty even across. should have it back in the water this weekend

 

[Frank Acampora]

Re: compression

Well, not to get you paranoid but 100 PSI is a little low. 90-100 is the compression ratio on the smaller 9.9-15 HP engines. Your 120 should be up around 145 PSI.

If your rubber-tipped gauge is slipping or being pushed off the plug seat, then it will deliver a low reading. Yes, the screw-in type will be more accurate.

Compression readings should be taken after the engine has run a while and has some oil in it. Readings on an engine that has been sitting a while will be low. ALL plugs should be removed and you need to crank the engine at least 4 turns or until PSI stops rising.

The good news is that all readings are equal. So, before going crazy, re-try the test. Then, after doing a re-test, put about one teaspoonful of oil in each cylinder and try again wet. If there is a significant difference, then you may have stuck rings and a decarb treatment might help.

 

[jerryjerry05]

Re: compression

Most auto parts stores will loan a good comp tester.

 

[jcjoyner]

Re: compression

thanks guys appreciate the input

 

[jcjoyner]

Re: compression

well the the compression is running about 140 straight across so I guess it's not to bad.
want to drop lower end to see about the impellar this is going to be hit and miss until I get a manual the bottom end oil is milkey so bought new gasgets for the dfrain and top screws. would like to put new seals in but am having trouble locating any thing.again chrysler 120 model 1207HC serial no.5208

 

[jerryjerry05]

Re: compression

Go to any Mercury dealer and get the seals for any sterndrive or outboard.
I think West Marine or that type store might carry them.
You really need a pressure test?

 

[Frank Acampora]

Re: compression

Most mercury dealers will not have records back past Force 1990. They will dismiss up if you ask for Chrysler parts or even early Force parts. You need to be persistent. HOWEVER from about 1978 through 1989, all the one piece lower units used basically the same parts--Oh, water pumps sand impellers were different, and the spool and seals were different but main seals were essentially the same. Do, if you do find a dealer with old stock, you can work with them.

NOW: I don't follow model numbers so I can't say what year your Chrysler is. HOWEVER: If it is a 2 piece lower unit with an old 18 spline , pin drive prop, then all seals are standard parts and can be purchased at a bearing supply store. Just try to bring in the old seal for comparison and try not to destroy it completely when removing it. ALSO: Strongly SPECIFY ALL STAINLESS construction.

 

[jcjoyner]

Re: compression

thanks At least I'm headed in the right direction

 

[jerryjerry05]

Re: compression

Didn't read it right,SORRY.Thought you needed the drain plug seals.
Valley Sales in Prudenville,Mi should be able to help with the seals