question for ALL. Seems most of the time when looking at dyno sheets for boats A/F ratio's are 12.1-12.5. when doesn't anyone like 13.5-14 ,,, just trying to understand

lean is mean,,but in a boat it will melt down.

Well for NA engines, around 12.8 will give the best dyno numbers.

Like he said. While 14.7 is stoch, best power can be anywhere from 11.7:1 to 12.8:1 depending on the motor.

Now, don't confuse widebands O2 readings on dyno sheets for what the dyno computes as AFR. I have seen them very as much as two points.

WOW!!!!!!!!!!!!!! I thought I had some bad ones in the past.... LOL thats something else

That stainless steel top hung in there!

i have a few that look a lot like that one!

Engine's are run at WOT on the dyno.

Therefore, all data you see is measured at WOT...including A/F ratio's.

Not on everyone's dyno. ;-) I make pulls at different throttle positions to verify that the tune up is right. I have seen a few different carbs come in with tuneups that have caused motors to melt down at cruise. They were right at WOT but 19:1 at partial.