Compression for a 115HP Yamaha 98-2005?

Im unsure of the year as a buddy is by the boat not me, what should a 115HP Yamaha compression be if it's around the year 1998-2005? I know the %10 rule but heard PSI numbers are lower with Yam's and didn't want to shy away from a good deal thinking the compression is low.


Thank You,
DamianJP

Re: Compression for a 115HP Yamaha 98-2005?

PSI numbers are irrelevant. The 10% rule rules.

Re: Compression for a 115HP Yamaha 98-2005?

If it is a 4 stroke, the compression ratio is 9.7 to 1. MINIMUM compression 135 psi. 70 deg. day, plugs out, throttle wide open. FRED

Re: Compression for a 115HP Yamaha 98-2005?

Hello

Just got back and the engine is a 1997 Yamaha 115HP 2 Stroke non-oil injected that is super clean, when the guy popped the cover off I was shocked. Just totally clean, Im not used to seeing a used engine so clean. As the rest of the motor is too, fresh water or some one cleaned it very good after salt use everytime.

Its on a 18.5FT Skeeter aluminium and I can get them both for $1000. The only down side is the trailer is %100 shot.

Has strong blue spark and 125+ PSI on all 4 cylinders. 3 cylinders were *DEAD* on each other on the same mark. Other 1 cylinder was a hair off the same mark.Well within the %10 mark. Now I didnt hold the throttle open, is that bad and can possibly give a lower reading?

Didn't hear it run yet, will tomorrow. Will have to pony tank it cause it has been sitting for a year. Possible carb/water pump job ahead. Skeeter hull needs TLC and small weld that I can get a friend to do it for $100.


Very excited my first aluminium bass boat and running a Yam. Gonna need a service manual, were can I get a factory one? Non seloc/clymer?

Thanks guys!!
DamianJP