Compression Bench Test?

[Intermediate Mariner]

Re: 1962 40 hp Evinrude
Hi,
I have removed powerhead (to repair clevis and bent shift shaft and already had cylinder head off as well to have machined). I had noticed pistons seemed pretty loose. After a few replys and looking around I found that they are pretty loose as a rule, but I should do compression test to be sure on rings.

The question: Can I perform a bench compression test without having to reinstall powerhead back onto exhaust housing as well as reattching starter? Perhaps with an air ratchet on the crankshaft top nut? I would do overhaul if compression fails rather than have to take everything back apart!!

Thanks~

 

[Vic.S]

Re: Compression Bench Test?

You need the head on and the starter operational to do the compression test. It measures the pressure built up in the combustion chamber when then engine is cranked.


See the item on compression testing in TD's "top secret file"

 

[F_R]

Re: Compression Bench Test?

You talking about an air ratchet or an air impact wrench? The air impact wrench on the flywheel nut will pound the nut down too tight, driving the flywheel taper down on the shaft, and destroy it. In other words, don't even think about it.

I don't know about the air ratchet, I've never owned one powerful enough to crank that motor.

 

[backyard mechanic]

Re: Compression Bench Test?

Sounds weird but there is another way... rope start. Yanking it a few times to find your compression isn't going to give you what the starter would but it will give you a good idea.

 

[surrender]

Re: Compression Bench Test?

you seem pretty far along, why not do the overhaul or complete rebuild? What was wrong that got you to this point?