Boat idles high

[cstello]

My 1999 sunsetter idles high. When pulling someone at idle it drags them pretty good. It also puts up a small wake when in the no wake zones. I read some where that it could be due to a possible vacuum leak. How would I find it and where are the vacuum lines?

[Dinsdale]

I eagerly await some responses on this topic as well. My 2000 SLXI idles in gear @ 4.8 mph according to my Perfect Pass. You get a lot of dirty looks in the marina unless you're constantly shifting in and out of neutral. I also have a bit of a whistle at about 2500 rpm which makes me suspect a vacuum leak.

[EZSnow]

how many RPM are you turning at a loaded (in gear) idle?

[trace]

Is this carbed or EFI? If it's EFI, clean the idle air control (IAC) on the throttle body. Should be something like a cylindrical item with a flange, screwed into the side of the TB.

You can check for vacuum leaks by spraying starting fluid around any hoses on the top of the motor. If it suddenly revs, there's your leak.

[electricjohn]

Vacuum leaks are the #1 cause of high idle. Make sure everything is tight on the intake section of your engine (manifold, plenum, and throttle body). If EFI the ECM will default to a high idle if the ECT (eng coolant temp) sensor fails, and you will have a trouble code.

[EZSnow]

What I was getting at is that inboards are very efficient at transferring thrust to the water, and seem to travel faster than most boats at idle. Your speed may be completely normal, and you'll just have to live with the dirty looks in the marina.

For the second post, a whistle at 2500 rpm might also be normal. Maintaining 2500 rpm without a load should not require much throttle opening, which may manifest itself as a whistle. I have driven a 6.0-powered prostar that whistled like crazy at most any setting between idle and full throttle. Of course it had some goofy hoodscoop on top of the motor box, so you heard EVERYTHING going on back there. A vacuum leak will most likely only be evident at or near idle.

Sooo, what is the idle RPM?

Edited July 2, 2008 by EZSnow