Ok, My gut tells me a good target Air fuel in the boat is 12-12.4:1, is that what you guys shoot for? I dynode and had engines at low 12's, in boat I see low 11's and sometimes 10.8 for a short burst, I am going to re jet for low 12's "in boat" I have widebands so I can keep eye on it all the time, is that the best target A/F?

Great timing. I ran my wideband for the first time this weekend, and while I didn't get much time to play in cruise mode or accelerating, my box stock QF 850 had me at 11.2 at idle and wot.

This heat isn't helping much either however your gut numbers are what I'd aim for or slightly higher. When you were in the 10 and 11's were you cruising or wfo. Some engine builders like to see mid high 11's for obvious reason however I think your pretty much spot on with your target especially under excelleration. Cruising at or around 3k is where I'd be jetting for and go from there.

Forgot to ask, your NA correct if I remember right?

yes N/A, cruising its pretty much same, maybe mid 11's at best, WOT it goes richer...

yes heat sucks too, I am looking at the little things now that all the bigger issues have been long gone lol

Ive tuned as few efi motors on the water and I tune for mid to low 13's at 70/75 map/2800-3200 cruising (9-10" vacuum), low 13's to high 12's at 80-85 map (3200-3400 cruising harder at 5-7" vacuum), high 12's in the 3600-4200 range and mid to low 12's in the 0-2" vacuum 4400 up hard to wot. A carbed motor will be a little harder since it doesnt have rpm/map based tables like efi but tune for mid to low 12's at wot, play with your power valves for cruise,you might end up a little fat somewhere to get the wot where you want it. This is all based on assumption motor made best power in mid 12's at wot on dyno and is NA, fwiw, Smitty

Great topic!, when reading AFR through a wideband.. Should there be a o2 sensor in each manifold? Or just one?

I used to tune on one in the boat but now use 2, using one is shaky since your not sure its correct, when you have 2 if they are not close you can figure out IF ones bad, one side is lean etc where if you tune on one thats off you could really damage something or at a minimum waste your time.

I run wideband on both engines one side or each engine, I have bungs to move them to other bank also if needed

Great info thanks guys. I will be adding a procharger this winter... And 1 o2 sensor in each manifold.