Does this seem right (compression)

[Philip Clemmons]

I don't have enough info on you, your ski, or riding style to make a call there. I can tell you I've seen similar numbers on "a few" pump gas boats.

Your dilemma is twofold.......you're not sure that the reading is accurate (maybe due to oil), but the motor isn't broken in either. It may go up or down depending.

If it were in my shop, I'd probably run it a while on the hose and recheck it. I'd make a call from there. Borrowing a friends gauge for comparison wouldn't hurt either.

Remember everyone's circumstances are different, as are there measuring methods. Battery strength, throttle opening, and opposing plug in or out can all affect readings. No one can accurately diagnose over the Internet, even with the best intentions.

Proceed at your own risk.

 

[Byeai]

My 718 jetmaniac motor with 35 cc domes has 215psi up front and 210psi in rear with about 13 hours on it

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[paczowski123]

Depends on riding style. WOT the you need more octane. If riding a short hull where your just riding around in circles and depending on your setup you may be ok. But not sure accuracy of your gauge. And that is all a gauge is. Just one reading of part of your setup.

I'm on a SN SJ hull..not a WOT rider mainly do what little flatwater I can or off small boat wake..do some yacht chasing but never WOT as I don't feel comfortable running it that way on a stock or modded boat..I have a feeling these numbers may drop after running it..if not I will be considering options to drop my compression numbers as I do not want to run higher octane unless I'm doing something special.

Phillip-I definitely understand diagnosing over the internet is not a science...i really appreciate all the input though! That's why I come here with my Q's for the professional opinions and recommendations, they are never ignored! I will do a light break in run, and use a friends high quality tester for another reading.

 

[paczowski123]

I'm on a SN SJ hull..not a WOT rider mainly do what little flatwater I can or off small boat wake..do some yacht chasing but never WOT as I don't feel comfortable running it that way on a stock or modded boat..I have a feeling these numbers may drop after running it..if not I will be considering options to drop my compression numbers as I do not want to run higher octane unless I'm doing something special.

Phillip-I definitely understand diagnosing over the internet is not a science...i really appreciate all the input though! That's why I come here with my Q's for the professional opinions and recommendations, they are never ignored! I will do a light break in run, and use a friends high quality tester for another reading.

Note: the test was done with opposing plug in, on a charged battery, throttle opened.

 

[kurtwolff]

Good, that is the proper way to test compression. It would be nice to check with another gauge, I have had two of those older Craftsman blue faced gauges go way out of whack. I replaced them with Matco gauge heads on the Craftsman hose assemblies, right around $10 right off the tool truck


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[paczowski123]

Good, that is the proper way to test compression. It would be nice to check with another gauge, I have had two of those older Craftsman blue faced gauges go way out of whack. I replaced them with Matco gauge heads on the Craftsman hose assemblies, right around $10 right off the tool truck


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Good to know! I'll have to look into just replacing the heads!