2006 F90 idles at 2000 rpm why?

[AverageBob]

I have a 2006 Yamaha F90 that has decided to idle at 2000 rpm upon start up and will not idle down. I have tried disconnecting the throttle cable, so it isn't a mechanical problem. I have also checked the wiring to the ISC motor and that is OK. I replaced the ISC motor and fixed the wiring last year.
Thanks

[fairdeal]

well, the engine can't do that without air

its either the throttle plate isn't closed,
the ISC valve is open,
or you've got a significant intake manifold leak

[AverageBob]

Well I disconnected the battery for awhile and it started up and idled down like it is supposed to and has been running fine. Go figure.

Thanks for the reply!

[CuttySpark]

Hi Bob,
my 40 hp goes in for service with a similar problem http://www.yamahaoutboardparts.com/f...a-th28831.html. It has been an intermittent problem for two years. I hope the mechanics can sort it out and will report back to the thread.

Cutty

[AverageBob]

Well it did it again, so I got to poking around and found that one of the 4 wires going to the ISC motor was loose. I slightly crimped it and it has gone out several times with no problem. I Don't know what year yours is Cutty, but they used aluminum wire for a time that likes to break inside the coating.

[CuttySpark]

I think mine is 2004. It has been in for service for a week now. The mechanics can't find anything wrong... When I last used it, it was impossible to get idle speed below 2000 without tricks, emergency enrichment handle. I'll get my Fluke out if the problem returns.