2003 Yamaha VMAX OX66 Compression

carp104

Recruit
Joined
Mar 1, 2011
Messages
2
Hey guys,

I am looking at purchasing a 2004 stratos with a 2003 Yamaha VMAX OX66 motor. The owner said he just had the compression checked and reads 90psi in all cylinders...he has receipt from mechanic for proof.

Does this sound a little low for this motor?

He also said he uses ring free in every tank of fuel and uses ethanol free gas. Can someone share their thoughts here?

Thank you
 

robert graham

Admiral
Joined
Apr 16, 2009
Messages
6,908
Re: 2003 Yamaha VMAX OX66 Compression

The only way to get a real idea of what you're buying is take the boat/motor to the river/lake and spend about an hour operating from cold start, idle, trolling, mid-range and wide open throttle. Compression readings and maintenance records are great, but there's nothing like a sea-trial to let you know what you've got. Good Luck!
 

SparkieBoat

Captain
Joined
Aug 17, 2009
Messages
3,643
Re: 2003 Yamaha VMAX OX66 Compression

I am not sure what the compression should be...90 is on the low side I think...but I have seen motors run great at that PSI. I agree with Robert on the sea trial..it will usually show any motor defects.
 

99yam40

Fleet Admiral
Joined
Sep 7, 2008
Messages
8,851
Re: 2003 Yamaha VMAX OX66 Compression

I am not a very trusting kind of guy, so I normally do all the testing myself and do not take the word of others as the absolute truth
 
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