What is a good symptom of this.

Crank and die, like its running out of fuel?

After a few trys cranking it starts and runs fine-turns rated rpm. Idles fine waiting on the trailer to be backed in. Turn off and start and no issue.

Should I keep a spare IAC valve on the boat, seems like a common issue doing a web search.

LC

Could be they usually throw and alarm at (constant) 4k then the two beeps below 4k. Will cause rough idle and stalling, I carry an extra and either the torx or allen wrench that holds them on. Make sure you change the gasket also if it is not sealed properly can lean out the engine.

just took the old one off, and like a dummy turned the key to see if it would actuate. It did and shot the plunger deep into the bilge. But the gasket looked like it could not have been sealing well at all, pitting on the metal. I have ordered a new one from my local dealer and dam they are $$$. 112.00 hopefully I can find some online cheaper.

You can use the car ones, I have they are about half. I had to get the gaskets from www.mercruiserparts.com

mine did not have gaskets except for the o ring.

Yours is a little different then I have 6.2s plus a different year. You could probably take it to a good auto parts store and match it up. I get about two years out of one whether its mercury or not.

I have some part numbers listed in this thread. I have 03 6.2's.
I bought one it had a paper gasket, the other I got about a month later and had a o-ring. Uncertain why but actually made a gasket out of gasket paper.
http://www.offshoreonly.com/forums/d...iac-motor.html

I found one on ebay last night for 17.00, plus I ordered one from my local dealer. i will compare the two and if the ebay unit is just like the merc unit, I will order two more 17.00 ones.

Cheech i read that tread yesterday, my iac is differenct, actually came on a 5.7 chevy not a ford v6 but very useful info for 6.2 users.

Cool, I was uncertain what the 350's had, just giving you a heads up in case you didn't search.

Bingo. Part # 2IAC12 is the cross number for the auto parts store.