Idle air valve failure

[asapmarty]

I have a 27 foot power catamaran with 2 DF175 Suzukis from 2006.
Took some friends to Cabbage key for lunch.
About an hour cruise at 30 MPH.
When I got there, I throttled down to enter the channel and the starboard engine quit. It would crank over but not start. I disengaged the shifter on the remote control and gave it a little gas while I started it and it ran fine.
it would rev up with the shifter disengaged and would slow down to just above idle, but would quit if I brought the throttle down to idle detent.
I figured it was the idle air control valve, as I have delt with these on other outboards. It was a long ride back at about 8 miles an hour.
Was wondering if anybody knows of a workaround to be able to get going in gear with a bad idle air valve. If this had happened 30 miles in the gulf, I would have been in trouble. Back at the dock, I ohmed it out and it has definitely failed.

[RussArran]

Safest way is to replace the IACV; it can be done without removing the flywheel, but you'll need a cranked screwdriver.

I've swapped out two of these valves on my DF175s - one on each. Both failures were caused by backfires after plastic fragments from the air intake manifold stopped the inlet valves closing fully. Check the IACV for sooting to the plunger.

How old are your engines - in terms of years/hours? There seems to be a pattern emerging about which Suzuki GB are in denial...

[asapmarty]

I did take the burned out IAC valve motor off with a ratcheting screwdriver.
The plunger seems to be a little burnt looking. I do not have the new one yet so I do not have a comparison as to what it should look like when new.
Its a shame they didn't just drill some holes in the flywheel so you could get to the screws on the IAC with a regular screwdriver.
How did you figure out that the shut off valve on the intake manifold was the cause of the IAC failure?
As for the age of the motors, they are 2006 DF175s. As per the tachometer, the motors have about 460 hrs on them.
I am curious about the cause of the failure and the damage to the valve motor windings.
Did you ohm out the old valve motor and find low resistance on one set of windings?
On mine it was low ohm reading between pin 6 & 5.

[asapmarty]

Russ of Arran is a wise Laddy indeed.
Did you have a fix for the sticking air intake vales in the intake manifold?

[RussArran]

Bingo! Lucky guess - or perhaps it's because I've had two top ends cleaned up (powerheads removed from boat and shipped to mechanic for camshaft and cylinder head removal, inspection, renovation and replacement - a job that is not without its costs*...) due to failure of the AIM flaps on each of my DF175s. Both late 2007 models, both with about 1100 - 1200 hours. Also replaced the AIM on our DF150 (2007, ~600 hours) as a precautionary measure. In both 175s the IAC motor was seized due to backfires which possibly occurred while trying to get the engines to re-start before the cause of failure had been identified.

You should have your top ends checked for contamination and possible damage; if you're "lucky" it'll just need a clean up for all the plastic pieces that are in there; if you're unlucky - well, bent valves, holed pistons, scored cylinders - let's just say I really hope your luck's in!

As both of my engines failed while at sea on different occasions (once while carrying passengers, then while returning to base having just disembarked passengers) I consider this to be a hazard to me, my crew, my boats and my passengers - and to anyone else who's unfortunate enough to possess any Suzuki DF150 or DF175 variant with this badly designed and manufactured sytem.

Suzuki GB have denied any knowledge of similar occurrences - despite me having pointed out to them many examples from around the world. They claim I'm the only person in the UK who's had to replace the AIM units - and they aren't interested in what's happened elsewhere. An interesting attitude for a corporation with a worldwide market place.

If anyone who's got loads of spare cash would like to start a global class action on product liability grounds, I'd love to hear from them.

* Costs - repairs in excess of £6,000 so far; and the loss of revenue to my business is a significant multiple of this.