Compression Test without a battery?

[NoSail]

can you get a compression reading on an outboard by turning thr flywheel manually? tx

 

[racerone]

Depends on the motor.------Some can be pulled over with a rope.-----That will give a good compression test.-----What motor ?----Model #

 

[NoSail]

1977 Merc 0115 Tower of Power (2 stroke) It does have a pull rope auxiliary start. I was turning the flywheel with a wrench and getting very low readings consistent across all cylinders (30psi except for #1 which was 60psi and that is the top cylinder and usually the problem one) I did not yet test #6

 

[racerone]

I suggest you remove the 3 bypass covers to look at pistons / rings.----Pull it over with a rope.----Perhaps ask a " wrastling , high school champion " to give you a hand pulling the rope.

 

[jimmbo]

The 115, consists of 6 relatively small Pistons, and once all the Sparkplugs are removed, it isn't too hard to turn over. I used to rope start my 84 115, as I was was too cheap to buy a new Battery. On a cold engine, it usually took 2 attempts for it to catch and run.

 

[NoSail]

I do have a good battery but the wiring harness is complete junk. I also have a remote starter. is it as simple as wiring the (-) side to the solenoid and the (+) to the starter switch or does it need to be stepped down?

 

[saltchuckmatt]

I do have a good battery but the wiring harness is complete junk. I also have a remote starter. is it as simple as wiring the (-) side to the solenoid and the (+) to the starter switch or does it need to be stepped down?

You could use an air impact gun on the flywheel nut.

 

[jimmbo]

You could use an air impact gun on the flywheel nut.

NOT a GOOD Idea, as that will lead to an Over Torqued Flywheel Nut, and possible Damage the Crank and Flywheel

 

[racerone]

Rope is easiest and does no damage to nut or crankshaft threads.

 

[flyingscott]

You could use an air impact gun on the flywheel nut.

An impact gun will not turn the flywheel.

 

[flyingscott]

To use the starter get some jumper cables. Attach the positive to the cable stud. Now touch the negative to the starter housing. To use the remote starter switch attach the positive jumper cable to the battery side of the solenoid. Attach the - to the block somewhere. Now Attach your switch the the positive terminal on the solenoid. Attach the other clip to the non ground side small terminal of the solenoid. Now turn the ignition key off to kill spark and do your test

 

[saltchuckmatt]

You could use an air impact gun on the flywheel nut.

I have a remote starter as well and I put one clip to + battery and the other clip where the signal wire comes from the harness. As far as the impact, while I've never done it, I see people doing it online and with all the spark plugs out I can't see a reason to not do it but with three negative responses I guess I wouldn't.

 

[jimmbo]

A large and powerful, non-Hammer Drill could be used. However Newton's 3rd Law would likely have the Operator going in Circles around the Engine

 

[NoSail]

Rope is easiest and does no damage to nut or crankshaft threads.

i did this and I got a higher reading. This has encouraged me to hook in the battery and remote starter. I think the faster cranking produces an accumulative pressure. "We'll see what happens". I'll let you know but I'm encouraged. Thanks for the discussion!

 

[NoSail]

To use the starter get some jumper cables. Attach the positive to the cable stud. Now touch the negative to the starter housing. To use the remote starter switch attach the positive jumper cable to the battery side of the solenoid. Attach the - to the block somewhere. Now Attach your switch the the positive terminal on the solenoid. Attach the other clip to the non ground side small terminal of the solenoid. Now turn the ignition key off to kill spark and do your test

doesn't this require a good wiring harness? The boat is in desperate need of a rewiring - I am looking to direct wire from the battery to the starter.
BTW - what is a 'cable stud'? thanks

 

[racerone]

You hook up a positive 12 volt cable to the solenoid.----You hook up the negative to the block.----Use the remote starter switch from 12 volt battery to one of the little terminals.----Push the start button and motor should crank .-----But 12 volts and wires can be a challenge to understand.

 

[Scott Danforth]

You hook up a positive 12 volt cable to the solenoid.----You hook up the negative to the block.----Use the remote starter switch from 12 volt battery to one of the little terminals.----Push the start button and motor should crank .-----But 12 volts and wires can be a challenge to understand.

or use a screw driver on the solenoid to jump the B and S terms