how to do a compression test on a engine that isnt running.

[legoman67]

Well, i pulled the 2 old engines from our boat because i found a good deal on 2 new engines, and the old ones didnt seem very hopefull.

Since then they have been sitting under a tarp in our yard, and i have salvaged afew parts here and there from them. Also i know most of the electronics onboard are bad.

I would like the check and see if there is any hope for these engines, or if they are just scrap metal, i drained the oil out of them yesterday and it was completely clean, no milky or anything.

how would i check the compression on the cylinders without running the engine? Also any other tests i can preform on the blocks?

 

[Don S]

Re: how to do a compression test on a engine that isnt running.

The first thing you have to do is block them up so they are solid and the flywheel clears the ground. Then hook up power and ground and crank it over, just like you would any other engine.
You will not get an accurate test, I like to run old engines that have set for a long time to just loosen up valves and rings and such before doing a compression test. You only need it to run for 15 to 30 seconds for that.
But if it turns over, try a compression test and see what you get.

 

[legoman67]

Re: how to do a compression test on a engine that isnt running.

they do turn over, without running i got between 50-90 on 7 of the cylinders and 110 on the 8th.

but i have heard this doesnt mean much, these engines probably havent run in 10 years at least

 

[Don S]

Re: how to do a compression test on a engine that isnt running.

but i have heard this doesnt mean much, these engines probably havent run in 10 years at least

After 10 years, you probably have rusty cylinder walls, rusty valves and seats & dry bearings.
Sounds more like disassemby is in order instead of a compression check.

 

[Bondo]

Re: how to do a compression test on a engine that isnt running.

Ayuh,...

Depending on their displacement,...
They're atleast worth a hundred bucks as Rebuildable Cores,...
If you can find somebody Needing them...

 

[legoman67]

Re: how to do a compression test on a engine that isnt running.

thats what i figured and why i jumped on the new ones. Ill just try to sell them as is, they arent worth spending alot of time on.

thanks guys, that little voice inside my head kept telling me maybe those engines are alright. but now im settled.

i have stripped the starters and had them rebuilt for the new engines, and ive reused the flywheels on the new engines, so there really isnt a whole lot of value left in them.

 

[180shabah]

Re: how to do a compression test on a engine that isnt running.

so there really isnt a whole lot of value left in them.

Hey, a couple hundred is a couple hundred - offsets a little fuel cost.