Checking Compression 1991 60 hp Johnson

[rhllmn]

What do I need and how do I check compression on a 60 hp 1991 Johnson motor? What should it be after its done?
Thanks
RH

 

[HybridMX6]

Re: Checking Compression 1991 60 hp Johnson

You will need a socket and ratchet to remove the spark plugs, and a compression gauge. Remove both spark plugs and ground them somehow (i.e. clamp to the block, AWAY from the holes). Put the gauge into one spark plug hole (it will screw in just like the spark plug did), and turn the motor over. If pulling a cord give it a few pulls, if electric start a second or two should do it. The gauge will go up and settle on a #, that is your compression. Write it down, and repeat the steps for the other 2 holes. What it should be varies, but generally they should be within 10% of each other (the highest and lowest #'s should not be more than 10% difference). I have a 1993 60hp and mine were 118psi. One was a bad cylinder and was only 80psi. Like I said, the #'s can vary by gauge, some read higher, some read lower, most important is to be within that 10% range. If a # seems way low, just ask us and we'll let ya know.

 

[TRACK CHECK]

Re: Checking Compression 1991 60 hp Johnson

Hi....
Some more about making a compression test on ANY motor.
If possible... at all times, engine should be run warm to its
normal operating temperature. Compression and also vacuum
changes with temperature. Vacuum is of great importance when
it comes to 2 stroke engines... specially to restart the engine after
a break/stoppage.
After running the engine warm and taking the cover off, dismantle the
sparkpluggs and mount the compression gauge in one of the holes.
Make sure you pull/tighten connector plugg even hard in each hole,
or you will ofcourse have an uneven reading. Now... by pulling the starter cord lets say twice for each cylinder - throttle should be WIDE OPEN.
So hold your hand on the throttle handle and turn it OPEN. This must
ofcourse be done on each cylinder - or you will have an uneven reading.
As previous writer... reading should be even.
By pulling a third or fourth time or even more... readings goes up to a certain
level... each cylinder test should recieve the same amounts of pulling or
"turn overs" by the electrical starter. After the test BEWARE... let the engine
cool of completely. NEWER remount sparkpluggs in an aluminium head and tighten HARD... it will/can destroy your sparkplugg threads.

 

[JB]

Re: Checking Compression 1991 60 hp Johnson

Do not open the throttle. Disable the ignition.

See the compression test instructions in the Top Secret File ^^^.