I have a pair of Merc 700sc motors with 250 hours, running perfect. The issue is I have had to replace ( IACT ) valve two times on one motor and once on the other motor. Any thoughts why ??? One thought is I have 20 minute idle out to the lake and 20 minute back in...

How did your engines act when tha IAC's went bad?

Engine alarm kept going off.

Did the engine idle any different or try to die.?

probably connector problem and or wiring of the connector.

Many things can cause a IAC to go out. Belt dust and or sound deadening material. Dirty flame arrestor need to clean it at least once a year.

over heat - heat around the IAC, Voltage resistance and that can cause a lot heat to and even melt the connector. High duty cycles and that will cause a lot heat to and can melt the connector.

Air restriction in the IAC system passages another killer and will cause high IAC duty cycles. Or I should say High PWM = Pulse width modulation.

Ran ok, but the plug-in got hot and melted. The computer box also went bad. OUCH $800. But it might not have been related to I-act issue...??

A bad IAC over time can knock the computer out. Have had close to 10 thru out the years.

Is there another source to buy the I act than pay Mercruiser the BIG dollar @ $150.00 OUCH. Been there three times already..

I do know this for a fact some aftermarket IAC's even that are a direct cross still do not work correctly compared to what Merc uses. I do know Merc IAC is made in the USA but do NOT know the exact parts source.

I do know this because I just looked at a 496 HO MAG this week that had a brand new BWD IAC installed that did operate correctly. I installed a new Merc IAC and all was good.

The engine as I was told, had a bad IAC so it was changed over to the BWD brand IAC but the engine seemed to run better but still sluggish. When I finally looked at the boat, it did not have a crisp idle and seemed like it was down on power. The scan showed 100 % available power and no faults.

how I found that the brand new BWD IAC was not working correctly was with the scan but I had to test it per Idle air control output tests and OHM testing the connector.

The connector tested out good per OHM's spec. change IAC to brand new Merc and it was day and night difference in engine running. A lot better and good to go. Just saying.

Aftermarket IAC info

http://www.offshoreonly.com/forums/g...ld-cost-3.html