This is why you do NOT use a harbor freight compression gauge

[Trooper182]

Ok so while trying to figure out my melting coupler issue I decided to check my compression again. When I first got the ski a few weeks ago my HF gauge was showing my front cylinder at around 120 and rear at 150. Was thinking for sure a rebuild was in the future. Well decided to rent a good gauge and retest today. And this is why you use a good gauge to test. On the right is the HF numbers and left is the rented gauge. Look how far off the numbers are! Two healthy cylinders.

 

[etemplet]

Yep. I drove a couple hours to look at a ski the guy said he was riding. I like it when they are running on the water as it is a good sign most of the important stuff works. So we check compression with his gauge and the ski is at 90psi. I said, "let me try my gauge" and the cylinders were above 140. I purchased the OTC gauges from Ebay for around $60. I wasn't sure thier quality either but OTC used to be a good name. Good Catch !!

 

[HawkX66]

I ran a compression test on a gauge that I've had in my garage forever. Both cylinders were at 90 psi. I was bummed, but then I thought about it. Both were even and I thought it was odd that they'd both be so low and even. I bought a new gauge and they read 125 psi. The new gauge was inexpensive, so the compression is actually probably even higher with a good gauge.

 

[KyleW2]

When I bought my tester I went and rented a tester from the store and compared it side by side to the one I bought. They both read the exact same, within 1 PSI per cylinder difference between the two gauges, tested on multiple different machines (Seadoo and a couple four wheelers). The gauge I have is an Innova 3612 which is available on Amazon for $28 as of today. Yes, that means it is cheaper than Harbor Freights gauge but it seems to work good for occasional use.