1999 3.1L OX66 200HP Yamaha (Couple questions?)

rjcamel2355

Petty Officer 1st Class
Joined
Apr 22, 2015
Messages
221
Hey guys,

I plan on picking up a new (to me) boat today, it's got a 99' 200hp 3.1L OX66 fuel injected yamaha on the back of it, from what I have read these are great motors.. so long as you

*Run ring free in them
* Run Yamalube in them
*Clean O2 sensor from time to time.

Any hints/tips or tricks on these? Is it true about only running yamalube? Does it have to be Ring Free or will seafoam do the trick like on the older carbed mercs?

I know this block is the same block as the 225, and 250.... What is the difference in the HP ratings? How possible/expensive is it to take a 200 and make it a 250? I assume it's mostly fuel and timing related, but I could be wrong... As this will be my first "EFI" motor.

Thank you,
 
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