I have a new Mercury 60 hp 4 stroke EFI. In short, what should the IAC valve sound like. ( a loose fan belt ?

Question

There is a noise that sounds like a bird chirping & just like a loose fan belt on a car. The Engine has a timing belt that seems loose, but I can't see how it can slip with all being notched. ( it is not a warning buzzer )

I just rode in another boat that had the same engine with no chirping noise. It seems to be too loud to be normal. It gets louder as you go faster, but don't seem to hear it at top speeds. When you slow down suddenly, it sounds like it skips gears.

A Mercury dealer told me it was the IAC valve.

I seem to here this more with the cover on & he had the cover off when he looked at it.

I would say the noise was not there when they looked at it.

Can a loose belt cause a loss in power?

Thanks for your comments.

Answer 1

I would take it to another Mercury dealer, if there is one nearby.  Don't tell them that you had it checked elsewhere, and see if they suggest replacing  the same valve.  If so, get it fixed.  This motor should run very quiet.

Answer 2

I would describe the sound of an IAC as a rapid slurping sound, that is only heard at idle and just above.  It would be the loudest with the engine cover off and you would hardly hear it with the it on.  

The timing belt on those models does seem loose but that is normal.  

If your hearing a high pitched chirping sound all the way up into the higher RPMs then you may have an intake leak or possibly an exhaust leak.  

A loose belt won't by its self cause a loss of power but if the belt slips and the camshaft is no longer in  phase with the crank then it can cause hard starts, loss of  power, and possible engine damage

Answer 3

You should listen to Mercury dealer because a Mercury like that should sound like a silent Moose f**t that you cannot smell.