I’m just wondering why people shoot for rich side on boat motors is it cause of the constant load? Mine mostly stays between 13-14 (autometer wideband) and I thought I was fine . Should I be fattening it up?
sorry nhguy about asking questions in your thread

It is the constant load, and a stuffy hot bilge doesn’t help. Many other factors contribute such as an engine with 8:1cr may be just fine at 14afr but the same engine with a 11:1cr won’t make it very far. There’s a lot of good threads on here with great input on what AFRs work best on what engine.

makes sense , thanks Baja rooster . I have a 350 mag with 9.4 to 1 and it does get warm in the bilge especially with closed cooling. I do feed it good gas but probably gonna look into jetting it up a bit then

At idle 13-14 AFR would be okay but I would add a little insurance in the upper rpm band. Plus you may not be seeing (monitoring) any knock or knock retard which can kill the motor and valve seats if left unchecked for a long period. At WOT you want to be closer to 12.5 - 12.8.

Not to highjack,How are Ya'll checking your afr's ?

Wide band O2 sensor.

What part of the manifold do you put it in,to keep it dry ?

Usually installed in elbow/riser but can be installed in special spacer between manifold and riser if you have room for the spacer.. The search function will bring up lots of info on how to install one.

I’m running a Holley Sniper with the O2 sensor in the stbd bank and a wideband on the port side just to keep an eye on things. I’ve had the best results with 14:1 at idle and have tried running 13.5 through the range and then dropped it to 12.8 with no discernible loss in performance so I left it there.

OP, you’re measuring the collective AFRs of four cylinders. So if the average is 14 then most likely a cylinder will be at 13 while another is at 15, and that’s the one that will burn up. That’s why we drop the average to under 13, to keep the leanest under 14. Intake manifolds seem to be the biggest variable. It’s shocking to see the Dyno results where an O2 sensor is in each header tube and again in the collector as the numbers are all over the place. Even a carb spacer affects it dramatically. Some tuners on a dyno with all of the O2 sensors and MPI can tune each cylinder individually will bring the numbers closer to 14, but that’s more to prevent a lean cylinder than gain performance.

Anybody make 02 spacers for EMI manifolds yet ? Bunch out there for OE and some aftmkt, just can’t find’m forcEMI