[raycapdevila]

I have a 1997 mercury 150hp efi and iv'e been using a 40:1 gas /oil ratio and im wondering if this is right?previous owner said to use 40:1.thanks,ray.

["G"]

Ray-
Most of the newer outboards run on a 50 to 1 gas to oil ratio. If your outboard manual says to use 40-1 then that is what you should use to be safe. It's when the engine is at WOT that the oil ratio is critical.
The EFI you have (as opposed to a carburetored engine with an oil reservoir that apportions the oil ratio with the throttle position) will have no oil ratio change at idle or at WOT. All this said, if the engine runs well with 40-1 oil mix, then don't screw with success.

[JB]

50:1 Ray.

[raycapdevila]

thank you i guess 40:1 can hurt the spark plugs???

[raycapdevila]

thank you for info my oil reservoir was removed from prev. owner i've been mixing in tank maybe i'll buy manual...