I am looking into purchasing a 2007 Yamaha two stroke outboard. The compression was tested while motor was warm and it tested 90 on all three. The guy is using a cheap gauge so don’t know if that could play into it. 90 seems low to me, but they are all dead even, not even off by 1. Is it really possible compression has dropped that much and they are all still perfectly even? I just wanted to get some input because it is a very far drive for me to go test on my gauge. Thanks in advance.
90 is not low.
Thanks for the reply, what is optimum compression on these? I only ask because usually I see closer to 120 when I see them pop up and both my current two strokes have 120-125.
I have been told by a couple Yamaha mechanics that the compression being within 10% from the highest to lowest cylinder is more important than how high the numbers are.
2006 Stratos 294 Pro XL.2005 Yamaha 200 VMAX 3.1L. 8" Hydro Dynamics Rapid Jack. Ultrex 112 I-Plot link. 2 Helix 10 Chirp Mega SI GPS G2N.
If you check with 5 different gauges you'll probably get 5 different numbers on the same engine. Sounds like you're good to go.
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