Compression Check 1983 70hp Johnson

"Can anyone tell me the proper

"Can anyone tell me the proper procedure for checking compression? Also, when you ground the spark plugs can you use alligator clips and put them anywhere on the motor? What readings should I get?"

"1. Before you begin, make sur

"1. Before you begin, make sure the battery is fully charged
2. Unplug the coil connector
3. Remove all plugs and examine them carefully for signs of a problem
4. Screw the compression gauge into the plug hole
5. Press the gas pedal to the floor to open the throttle plate, and keep it at WOT (wide open throttle) for as long as you’re cranking
6. Turn the ignition to the ON position, and hold it there for a count of four revolutions (do not turn the key on-and-off four times). On each rotation, the gauge needle will jump slightly less than the previous one.
7. The last number the gauge jumps to is the compression for that cylinder.
8. Repeat for each cylinder.

Update: It may take more than 4 revolutions to get a stable reading; crank for up to 10 seconds or until the needle stabilizes, whichever comes first.

Note: If your battery is weak, the engine will turn over slower and give you lower readings.

anything over a hundred is good readings of 120/130 are excellent,yes clips are good,just dont hold it and stand in the water (i did that once) "

"Thanks for the quick response

"Thanks for the quick response Charles. If I unplug the spark plug at the coil do I still ground the coil? Also, should I have the muffs on?"

no muffs needed/yes ground coi

no muffs needed/yes ground coil.even better disconnect the tether cord if so equipped

Thanks again Charles.

Thanks again Charles.

"The tether cord, you mean the

"The tether cord, you mean the kill switch on the control box? If I pull that off that will kill the ignition right? That's would be easier."

yep

yep

"So if I pull the tether cord

"So if I pull the tether cord which makes the ignition inoperable, do I still have to groung each spark plug to the engine? I just want to make sure because I don't want to fry my electrical system. Thanks again."

No need to ground the plug wir

No need to ground the plug wires as the ignition cicuit will be non existent with the tether cord pulled.

Thanks Joe.

Thanks Joe.

O.k I just finished checking t

O.k I just finished checking the compression and I have 120 psi on all three cylinders. How long are the cylinders supposed to hold that pressure? I guess this is what you would call a leakdown test.

Crap!!!!! I just read the prev

Crap!!!!! I just read the previous post about the procedures and I didn't make the throttles wide open. Does this make a difference in the readings?

"u DO NOT..have to have the en

"u DO NOT..have to have the eng warm,..nor,do u need to grnd the plug wires,...nor ,do u need to have throttle open......on a 2 strk...for comp ck......"

How long are the cylinders sup

How long are the cylinders supposed to hold their pressure? Sorry about all the questions.

"all u r trying to do,..is get

"all u r trying to do,..is get a 'pump-up' pressure....that is the first step,and 99% of the time finds any prob....if a person/mechanic,needs to get more info on sticking rings,wear etc...u do a 'LEAKDOWN' test.....2 diff gauges...in fact,.......its like pressure and vacuum testing lower units...99% of the time,u can find the leak,by pressure ONLY....i prefer,p&V..after i reseal one...and do it,..1-2 x...every 2 wks.."