AFRs for Holley sniper conversion?
 

Someone over on the Holley forum suggested I post my question here. I’ve converted my searay 3.0 Mercruiser to a Holly sniper EFI system. Overall it’s great, still have a few little things I’m working out and I’m currently tuning it. I was wondering if AFRs for marine engines are much different than automotive?

Out of the box the target AFRs are:
13.5 idle
14.0 cruise
12.5 WOT

Most of the time I’m cruising at 75% or idling around the canals, occasionally pull a skier. I know you all deal with much higher performance boats but any guidance would be much appreciated.

Ayuh,..... I suggest doin' some spark plug color reading to see what's goin' on,......

Do a run at xx rpms, for xx number of minutes, then fairly quickly, shut it down, 'n pull the plugs to observe the plug color to id how rich, or lean it's running, at that rpm / load setting,....
Than adjust accordingly,....

cruise is a little lean,,I'd be monitoring the knock sensors.afr for cruise 13-13.4.you running the afr sensors all the time?

So let me ask you this. What color does a plug look like if the AFR is 13.0. What does the plug look like at an AFR of 13.5? etc.

Idle AFR is fine.

Cruise should be closer to 13.2.

12.5 WOT is fine as well.