Idle gets worse when warm, and has hot start issues

350 Chevy
16168625 ECM
Application...BOAT

Guys..........

Just want to get your thoughts. I havent had a chance to log this year yet, except for in the driveway. I will this week. Put the system in the boat last year and it runs down the river beautifully. I still get a SES light while cruising down the river at 3100 and shows a Lean O2 condition. This happens occasionally and I will adjust with Howell EFI help as they set up the ECM origionally and is close to my house. No biggie.

It has a slightly erratic idle when you start cold and warm, varies up and down 75 RPM both up and down. I looked for vacuum leaks, but all lines are plugged except PCV (Mentioned in my previous thread) Any other suggestions. It seems to get more erratic when warm. Dont understand. Any other things besides vacuum that could be the cause. Will the log show anything, if examined by trained eyes?

Also, if you are cruising, the temp is 150F and is always constant. When you come close to idle after a cruise, the temp goes up to approx 170 for approx 5 minutes or so, until river water cools it. It has always done this. During this hot period, if you shut engine off, it cranks back up super slow and show what I call hot start or Detonation of sorts. Is there anything I can do to the ECM if another thermostat doesnt help?

As usual, I appreciate and thank you in advance for your input.

Thanks

O2 lean I would check fuel pressure.

Forgot the boats temps are so much lower then cars, that will cause many issues until fixed in chip. Going to have to use Off Idle fuel and spark tables in Idle tables because without VSS it will always be in idle tables...

For the start and idle issue knowing what IAC count is would be a big help. Could try and open throttle blades a half turn and try.

That boat motor was never designed to run 14.7 to 1 AFR... which could also be an issue...

I assume you have a dry exhaust system?

It's a wet exhaust but he had some machine work done to allow use of O2 sensor, but I don't remember if it was one cylinder or bank?

Ive tuned a couple boats on our lakes open loop nicely.

interesting. I was wondering how you would get an o2 sensor to work in a heat exchanger.