9.9 Cold compression 95 psi

[2strokesmoke]

I have a 2000 9.9 2 stroke, actually a 15 since I changed the reed valve assy. Top was at an avg. of 97psi and the bottom was an avg. of 93... after the impeller flying apart and running (slowly for 1-2 minutes). I know thats good becasue they are so close in number, way less than the 10% always metioned. Also, I forgot to open the throttle up to WOT.

Will compression be higher when warmed vs. cold, and how much diff could or should I expect to see? Ill be doing agian warm this week, wondering what I could see.

I have heard mixed opinions on WOT or not, will that really make a difference? Choke or no?

When I look into the spark plug holes, should the cyl.'s be black and coated looking or clean and shiny? Low hour motor I bought last year, until now (which is my fault for not checking the impeller) this motor has been textbook flawless.

Off subject but is it good to run the carb dry, whats the frequency of use when you shouldnt worry about doing it?

Thanks for the help

[99yam40]

From what I understand the throttle position does not matter on a 2 stroke motor as it will get what it needs from exhaust to pump up the compression.

If you want to see for yourself then try it at WOT and closed throttle to see the difference.

I do not like running a motor until it dies. Motor runs lean and you can never suck all the fuel out of bowls so what is left evaporates that much sooner leaving residue.

Run often or drain bowls if stored for long periods( month or more)
Just an opinion

[2strokesmoke]

Thanks for the reply, what about the numbers hot vs. cold... any diff.?

[99yam40]

warmed up should be a little higher than cold, but could be the gauge is what gives the lower #s

[2strokesmoke]

Good point, I have read they need to be calibrated regularly... I rented this one from Autozone so Im sure its been used a good bit and likely never been calibrated.

Thanks for the replies !