choosing a compression gauge

[monk-monk]

i have a '72 merc 1150 L6 outboard and want to do a compression test. i do not presently have a tester and im wondering when i go to buy a tester, what would be the best brand to buy...i know the no.6 cylinder is hard to get to so im hoping to get one that is compatible and trustworthy!

 

[mikegj]

Re: choosing a compression gauge

I got a loaner from auto zone, was about 40.00 and got it back after I returned it in the same condition. It worked fine for the short time I needed it. (didnt see a reason to purchase one)

 

[monk-monk]

Re: choosing a compression gauge

thanks mike, thats one avenue to consider, but...i have used tools from the autozone loan-a-tool program before...and i must say that the majority of the tools i've used from there were in "less than steller" condition...people just seem to abuse these tools and therefore im not sure i would trust using a loaner tool.

 

[5150abf]

Re: choosing a compression gauge

Got mine at Auto Zone, don't know brand but it is purple.
Had it for a couple years with no problems.

They are probably pretty much all the same unless you get it at
Dollar General.

 

[tashasdaddy]

Re: choosing a compression gauge

with the merc, besure to get one that has the hose, that screw into the spark plug hole, or you will never get to the bottom cylinder.

 

[Silvertip]

Re: choosing a compression gauge

You don't have to spend a bunch of money on a compression gauge that you will seldom use. You can get them at an store that sells auto supplies. Most farm stores have them in the auto dept. generally around $30.

 

[SeaKaye12]

Re: choosing a compression gauge

Remember that when checking compression; looking for similiar values on all your cylinders is more important than specific numbers. Most of the pros here say that the variance shouldn't be more than 10%.

Therefore, the accuracy of the gauge isn't all that critical; as long as it's consistent.

Most of us have bought gauges at Sears or similiar, and they do just fine.

But, like tashasdaddy said...get one with a detachable hose...one that threads into the head. I once had a really simple one that just pushed in; that I would not recommend.

Hope your numbers are up.... (As opposed to your number being up...)

Chuck

 

[monk-monk]

Re: choosing a compression gauge

thanks to everyone that answered! Lord, im almost scared to check it for fear of bad news! it runs darn good now but i think its the wisest thing to do as i have never checked it for the two years i've had it! its a '72 Merc 1150...how much compression should it have?

 

[tashasdaddy]

Re: choosing a compression gauge

i would want to see that they are all with in 10% of each other. 100 psi or higher, higher the better. But, remember that each guage is different, and the number is not the most important reading, the difference between the reading it more important. if you had 5 cylinders at 125, and one at 90, then you need to be concerned why the one is low.

 

[angler53]

Re: choosing a compression gauge

Check this out. We've all herd about the leak down test. Here are instructions to build one. It doesn't cost much to make. The major cost is an air compressor if you don't have one.

http://www.xs11.com/tips/misc/misc3.shtml