Compressions for the following two.

James R

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Feb 1, 2007
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Can anyone provide me with the good compression numbers for a 2012 Yamaha FX HO and a 2013 Kawasaki STX 15F. I am looking to purchase one or the other.
Thanks.
Jim.
 

QBhoy

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Can anyone provide me with the good compression numbers for a 2012 Yamaha FX HO and a 2013 Kawasaki STX 15F. I am looking to purchase one or the other.
Thanks.
Jim.
I can’t say for the Kawasaki, but from memory, the Yamaha should be at least 160 and ideally about 180/190 psi roughly. That’s what my FXHO was anyway. The 1100 mr1. Yours may be the newer 1.8 though. But even at that. Certainly upwards of 160 for sure.
 

James R

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Feb 1, 2007
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2,660
Thanks QBhoy.
Took a look at the Kawasaki as the Yamaha seller wanted too much.
Bought the Kawasaki. 1500 motor. Compressions 155 on all four and runs without any knocks or rattles. Has been used in fresh water and is in nice condition.113 hours on it.
I am satisfied. Is there anything, apart from start the motor before turning on the flush water, that I should be aware of?
 

QBhoy

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Joined
Mar 10, 2016
Messages
8,286
Thanks QBhoy.
Took a look at the Kawasaki as the Yamaha seller wanted too much.
Bought the Kawasaki. 1500 motor. Compressions 155 on all four and runs without any knocks or rattles. Has been used in fresh water and is in nice condition.113 hours on it.
I am satisfied. Is there anything, apart from start the motor before turning on the flush water, that I should be aware of?
Just the usual jet ski stuff really. Make sure it’s all water tight. The ride plate and intake bolts etc all tight and not snapped. Easily done when removing or tightening too much.
Grease the greasing points. Likely a zerk on or near the coupling from engine to pump. Steering and trim at the nozzle out the back. Steering and throttle cables etc. battery health on these wee things is critical. Easily done to let the battery fail. Get a maintenance charger for her, when not in use. Or you’ll be buying a new battery every year for sure.
Make sure the tolerance between the impeller (prop) and wear ring is acceptable. Should only be a few mm at most. Or it will just not go well at all.
Plugs are easily fouled on any 4 stroke ski I’ve had. Make sure these are good..leads and coil packs too.
Some skis (not sure about the Kawasaki at all) like the Yamaha 4 strokes all usually have an oil catch tank. Some are fooled into a false oil level when checking the dip stick on these. They show no oil until it’s been ran for a few mins then stopped and allowed to settle. Those not in the know, think it has no oil and then add…meaning there is then too much oil. That then comes back up through the filter and causes issues. Check the details around yours maybe. See if you can get a manual. Yeah. Start engine first. Then water. Opposite when stopping. Best of luck.
 
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