DF250 Stalling /Not Starting at Idle

[ESDiver]

I have a 2008 DF250 with 1100 hours. Ran offshore 29 miles and the motor died when I shifted to neutral. No alarms or lights. Motor cranks but won’t start. Thought it was a gas issue but all filters are OK. Starts ok in neutral with a little throttle advance. Stalls as soon as it goes back to idle. After playing for a while I was able to quickly get it in gear and run back. Motor runs fine if you can get it in gear. Speeds are correct at various RPMs. Throttles up and down normally. Looking online I suspect it’s the Idle Air Control Valve but not sure if it may be something else. Seems like that would be easy enough to replace. Any advice would be appreciated.

[Moonlighter]

The other possibility is the anti-syphon valve on the boat’s fuel tank. This is a quite common issue with those valves and your symptoms sound very similar.

We had the same symptoms a few years ago on a mate’s DF300.

It would stall at idle when started, or when we dropped back to idle after running at speed. If we pumped the primer bulb it would firm up and we could start it again, and if we were reasonably quick we could get it into gear, get the revs up, and onto plane. Once on plane all was good.

The solution was simple. I unscrewed the valve from the tank took it to the workbench and punched out the little ball, spring and seat that makes the valve work. Which left us with a straight through barb fitting, which I then reinstalled on the tank. You could just buy a new barb fitting for a few $ if you dont want to punch the internals out of the valve body.

Problem solved.

Why not give this a try and see if the problem goes away? Its a simple thing to do and you can easily do it yourself at zero cost, apart from a bit of sealant on the threads. Plus, it gets rid of a potential future problem anyway because those anti-syphon valves are just a problem waiting to happen.

[cprice11]

After Red lowrey put me on the right track, I looked in the factory Suzuki manual ,found where the part was on the motor, took it out and put a ohm meter on the IAC pins as per the manual. The ohm readings indicated a short .I found the same Mitsubishi made part at autozone car parts for half the price of a boat part site. (saw some very cheap parts on Amazon Not good reviews) It then ran fine. Idle RPM was fine. Had to change this part on both my 07 DF 150s. I managed to change them without taking the flywheel off.