compression test results

[Livewire]

I searched the threads and kind of got idea what good compression should be on mr-1's ho. So today we did a test on both motors and had roughly 119-120psi on every cylinder. Those numbers are low, but we tested on cold motors at about 35-40 degrees Fahrenheit with the throttles in neutral.

You guys think that would be good readings for the circumstances?

 

[robert843]

I'm not sure of the PSI number but if they all read about the same that's probably good.

 

[Scottintexas]

Are you experiencing some sort of problems? are you turning 10k and able to go somewhere between 42-50mph?

I'm not a mechanic but it seems like you either didn't test correctly, have the throttles full forward or you may have a problem,
looks like min. is 157 psi and difference of no more than 14 psi

 

[Jgorm]

Need to test with 20a+ battery charger, lanyard out, full throttle until the gauge does not go higher. Reset and repeat at least one more time. I got about 200 cold and 230 hot on my good cylinders.

 

[Livewire]

Appreciate the replies guys. No problems with running 10k rpm or hitting 45+ mph on the test drive. I was just wondering if my readings would be consistent with cold motors at just above freezing. Also this was done with throttles in neutral. I will admit this was my first time doing this test and just bought a cheap harbor freight tester.

I was unaware that low charged batteries would affect the readings. I was pretty much checking to see if all 8 cylinders were within 5% or so of each other. Which they were.

 

[itsdgm]

Appreciate the replies guys. No problems with running 10k rpm or hitting 45+ mph on the test drive. I was just wondering if my readings would be consistent with cold motors at just above freezing. Also this was done with throttles in neutral. I will admit this was my first time doing this test and just bought a cheap harbor freight tester.

I was unaware that low charged batteries would affect the readings. I was pretty much checking to see if all 8 cylinders were within 5% or so of each other. Which they were.

That could be your problem. I bought a harbor freight compression tester and it seemed like it was reading almost exactly 50% of actual pressure (i compared it on a small engine with another tester). I returned it no less than 3 times until I switched brands. Harbornfreight has two brands they sell. The second brand was way more accurate. I believe my numbers initially were about 95, then 190 with the other gauge.

But like stated above. If they're all within 1 psi, you're probably ok. But take the gauge back

 

[Livewire]

That could be your problem. I bought a harbor freight compression tester and it seemed like it was reading almost exactly 50% of actual pressure (i compared it on a small engine with another tester). I returned it no less than 3 times until I switched brands. Harbornfreight has two brands they sell. The second brand was way more accurate. I believe my numbers initially were about 95, then 190 with the other gauge.

But like stated above. If they're all within 1 psi, you're probably ok. But take the gauge back

Appreciate the feedback on the HF tester. Pretty much bought the HF tester for piece of mind. Been reading here and took everyone's advice to not buy without doing one, but the boat ran perfectly and drove great last weekend. Went back this past Sunday and purchased it. Fresh water boat and looks like new for its age.

Thanks again for your time.