Engine dies while idling in drive (Mercruiser 350, Alpha I Gen II)

[vtomgardner]

Ok, this one is baffling me a bit. I started the engine earlier this week. No problems. It turned right over.

I put in new gas. And let it idle for about 15 minutes docked. No problems.

I drove out of the cove, and did about 10 minutes at cruising speed. No problems.

I came back, and once I got into the cove I slowed down to no wake speed (just like I did while leaving 10 minutes earlier). BUT, it sputtered and stalled. It took a few tries to restart it, I revved the engine a bit, and made it back to it's slip.

I replaced the fuel filter thinking it was some left-over bad gas. I did the same thing the next day, and had the SAME problem! Stalling, in practically the exact same location. Again, I was able to restart and get back to the slip.

I'm thinking about slightly increasing the idle speed. But, I'd love to hear your suggestions

 

[scoflaw]

The ecm controls the idle speed, so not your problem. IAC comes to mind though.

 

[DWABoat]

What year?
Are you carburated or fuel injected?

 

[vtomgardner]

What year?
Are you carburated or fuel injected?

It's a 2001. I know I sound like an idiot, I think it's a carburetor, because it has a flame arrestor on top. But, I was told by the previous owner that it's fuel injected (But he seemed to be guessing). So I honestly don't know.

 

[DWABoat]

Could be either around that year. My 2001 is fuel injected but my buddies Chapparel with a Mercruiser has a carburator.
If you are fuel injected, you may have temperature or some other sensor going out, so when engine is warm it is looking for a signal that is wrong.
If it is carburator then maybe your jets have some goo that only matters at idle when the engine is warm and choke is off.
I wouldn’t start messing with settings until you find the problem. Get those off and it can get ugly.

After the engine is warm and you go back to idle, is it only running rough when in gear or in neutral also?

 

[DWABoat]

Oh…and you need to pull the Backfire Flame Arrestor off and look (not necessarily while engine is running). My fuel injected 2001 has throttle body fuel injectors and still has a flame arrestor.

 

[superwa]

Sounds like you need to reply the IAC valve. A very common problem and easy to fix. Hopefully that’s it.

 

[Spaced_Out]

Anyone experienced an issue like this: While running at slow speed, about 1000 rpm, starboard engine shuts down. I initially thought it was fuel starvation because starboard tank was low, and my fuel gauge is hinky at lower levels. However, came into the fuel dock on port engine only and topped off, it was not out of fuel and it cranked right up at the dock. So, went back out on the main body of the lake and brought it up to a plane. RPM on the starboard side was not keeping up with the port side, and when I came back down to slow speed it was taking more throttle on the starboard side to keep the RPM up. Eventually the starboard engine shut down again. Returned to the marina on port engine only, and when back at idle speed started the starboard engine back up and successfully backed the boat into the slip using both engines, no troubles. My gut feeling is there is something causing the starboard v-drive to require more force to turn it than the port but I do not know for sure. What are my best first steps here to validate the source of the problem?

 

[superwa]

It could be related to the IAC valve? Easy thing to replace and see.

 

[scoflaw]

Not the IAC. Start with a complete tune up, filters and fuel pressure check.

 

[vtomgardner]

Could be either around that year. My 2001 is fuel injected but my buddies Chapparel with a Mercruiser has a carburator.
If you are fuel injected, you may have temperature or some other sensor going out, so when engine is warm it is looking for a signal that is wrong.
If it is carburator then maybe your jets have some goo that only matters at idle when the engine is warm and choke is off.
I wouldn’t start messing with settings until you find the problem. Get those off and it can get ugly.

After the engine is warm and you go back to idle, is it only running rough when in gear or in neutral also?

As for the engine, I finally had a chance to get under the flame arrestor, it's a throttle body fuel injection. I did replace the IAC and the problem is still happening. So, this is officially getting out of my experience level -- Hopefully the mechanic will be by in a couple of weeks. I'll post an update once it's been identified and fixed.

 

[atrick]

Did you make sure the fuel tank vent is open and not plugged.

 

[vtomgardner]

Hi all, just to give an update, after installing the IAC valve and it stalled out a couple of times, I called the mechanic at the Sea Ray dealership in the LKN area (MarineMax). They repeatedly lied and falsely promised they'd send someone out. They didn't. So, after talking to a friend, he suggested that I just try to run the engine again and see -- his theory was that the recent failures was the engine's computer still adjusting to the new IAC.

So, I ran it for 15 minutes at idle, and no issues.
Then I ran it for 30 minutes at idle, and no issues.
Today, I cruised around the lake for 30 minutes, with three times idling for about 5 minutes. Again no problem

So hopefully the new IAC is working and the issue is done. I'll let you know if things get weird again!