Boat problem merc. 350 mag

(curt489) · (curt489) **Join Date: Feb 2008** 02-16-2009, 8:30 AM

I took my boat this saturday just to get it ready for the summer. Problem is that when i stop from crusin speed to neutral the motor stalls and shuts off. But it cranks right back up runs fine. At full throtle the boat seems to be missing. I'm thinking maybe timing. I have also heard of a neutral safety switch do these switchs go bad? Any feedback would be great.

Its a merc. 350mag in 2003 elite v drive 240 hours centurion.

(k_b_stephens) · (k_b_stephens) **Join Date: Jun 2008** 02-16-2009, 8:44 AM

Check the distributor. Mine was skipping real bad and thought it was bad gas, but ended being corrosion on the contacts. Took a dremmel with a wired brush attachment and cleaned it right up.

(towboat_222) · (towboat_222) **Join Date: Feb 2007** 02-16-2009, 11:01 AM

is it a mpi boat. If so might be IAC valve.

(curt489) · (curt489) **Join Date: Feb 2008** 02-16-2009, 11:36 AM

Ken, I will have to look tonight when I get home I think the motor is MPI though. What is an IAC valve and what does it do?

(towboat_222) · (towboat_222) **Join Date: Feb 2007** 02-16-2009, 11:44 AM

It adjust the air that goes into the motor. We have trouble sometimes after sitting for a while. It usually wont let the motor idle but lets it start up fine and run sometimes will act up on top end.

(rdmb) · (rdmb) **Join Date: Mar 2007** 02-16-2009, 5:46 PM

http://www.marinepartsplus.com/catalog/mercruiser/serial/350_MAG_MPI_ALPHA-BRAVO/884712/7585-80

Look at part #6. It is called the IAC Muffler. This is what Ken is talking about. I had problems with mine causing it not to idle. It would start up fine then run rough and die. Frustrating trying to pick up downed riders etc. It was oil soaked and wasn't letting enough air in the sensor. It's a $1.14 piece of foam that most certified Merc dealers will have in stock. To see if it is the prooblem, just take it out and run it. You'll hear a hissing noise at idle (hence the name "muffler"). If it idles and doesn't stall on decel, you know what caused it. Now that I think about it, I should have bought a spare to keep on the boat. Good luck. Oh yeah, I don't know anything about the web site I linked to. It was just the first one I found that had a good diagram to show where the part hides in the throttle body.

(curt489) · (curt489) **Join Date: Feb 2008** 02-16-2009, 6:34 PM

DAVE.
That sounds just like whats happening. i get this werid hissing sound sometimes and then it will stop after a little bit and start again. i will have to try that piece. thank for all the suggestions.