50hp Evinrude compression

[Calhoun85]

I'm looking at a 1993 Evinrude 50hp Outboard, Model E50BELETD, to buy. I would like to know what the compression specifications are if anybody has a manuel handy. I will be testing it today and will reject it if the numbers are too low per specs.
Thanks

 

[racerone]

No numbers published.------They should be even.-----I would expect to see 140 on my tester , but there are many different tester and your results may vary.

 

[Calhoun85]

Thanks racerone. I just winder where the acceptable cut off would be as long as they are within 10% of each other?

 

[gm280]

:welcome: aboard Calhoun85 to iboats.

The compression numbers can be most any number, but I think folks start to get concerned when they start to drop below 90 PSI. I read and see so many compression numbers posted, and they vary all over the place, and that is do to so many other things then just true compression values. The closer they are to each other the better. The actual value is subjective because of meters, seal of the meter used and so many other things... I have a '76 Johnson 40HP engine and I ordered the actual manufacture's shop manual for it because I was rebuilding it. And there is nowhere in that manual that specifies what the compression values should be...Hope that helps you out some...

 

[Drummerhowie]

Something else you may want to do is pull all the spark plugs when you do your test. My Marine Mechanics instructor mentioned he'd seen several instances where you could have a blown head gasket affect the readings from cylinder to cylinder, but by pulling the plugs you are going to get a more accurate reading.while the plugs are out, you can turn the flywheel by hand and look at your pistons come up. When they start to go back down, take a round or blint tool (I usually use a 3/8" socket extension) and gently push on the top of the piston. if the piston goes down a tiny bit (has play) you may have loose wrist pin bearings. Just a couple things I do when looking at a motor.

 

[bonz_d]

With the gauge I have I normally find 140-150 on the 2 cylinder 50hp models. Below 120 I'd 1st try a different tester, if same then a couple drops of oil in each cylinder and recheck.

 

[Drummerhowie]

....another thought too is that if you open the carb(s) wide open, you may likely see arise in compression. (More air is being drawn into the cylinders.)

 

[Calhoun85]

Well the #1 cylinder has 135 psi and the #2 has 140. This was done at operating temp with both plugs out and WOT. Repeated 3 times. I think that is acceptable compression. Now I need to get some new spark plugs as the old ones looked like they had been there awhile. Thanks to everyone with the advice.