Merc 2.5 efi whistle at low idle.

**Mx722** · 03-11-2017, 08:00 AM

Hey guys new to the site and was looking for some help. Last summer near the end of the season at low idle coming into the dock my motor started making a faint whistling sound , popped off the hood and almost sounded like it was coming from the flywheel. Motor runs perfectly fine other than this noise. Has anyone ever had this happen ? Or could give me an idea of what's up. Thanks.

**tunnelmike** · 03-11-2017, 11:27 AM

I had a 260 that would do that but never found the cause. Sounded like a bad vacuum leak on an old Chevy ! Mike

**Mx722** · 03-11-2017, 11:30 AM

That's what it is a 260. Thanks for the reply mike. So your saying I have nothing to worry about then ?

**Capt.Insane-o** · 03-11-2017, 11:36 AM

Prolly from the horn.

**tunnelmike** · 03-11-2017, 01:14 PM

I was told it was from the idle holes in the butterfly being drilled oversize and a bored horn. It's the only one I've heard of till now that did it. I traded a stock 2001 200 for it and after not feeling comfortable with the noise I traded it for a Honda Rancher.
They are expensiveto rebuild , I would try a stock horn to see if it goes away. I would feel better if someone with knowledge would say its good to run !

**Mx722** · 03-11-2017, 01:33 PM

its weird because it started after a WOT run across the bay in front of the house ,At first it would whistle then I would shut the motor off and restart and it would go away. After a month or so of it doing this it would whistle consistently at low rpm and not stop. And the horn you had mentioned do the Efi's have that ? I've looked at pics and mine doesn't have that sticking out the front like I've seen in pictures. This is the first 2.5 I've owned so it's new to me.

**Mx722** · 03-11-2017, 01:34 PM

Do the Efi's have a horn ?

**Mx722** · 03-11-2017, 01:45 PM

And as far as I know the motor is stock other than the lower unit. Nothing has been bored or touched. I don't I'm just hoping I can diagnose the problem and have it fixed because I love the power of this motor. And the sound ��

**tunnelmike** · 03-11-2017, 02:45 PM

If its a 260 it should either have a horn or SVS front. Is this an aluminum colored motor ?

**JAFFA** · 03-11-2017, 02:55 PM

You say it seems to be coming from around the flywheel, Id be checking the oil feed to the top bearing.

**Mx722** · 03-11-2017, 03:05 PM

It seams that way but the motor is so loud at idle it's hard to make an accurate determination. Thanks for your opinion man I'll look into it

**WillySteve** · 03-11-2017, 06:55 PM

Early, '84ish oval port 2.5 efi's had an updraft horn, still with the single butterfly!

**BUZZIN' DOZEN** · 03-11-2017, 07:42 PM

Originally Posted by WillySteve

Early, '84ish oval port 2.5 efi's had an updraft horn, still with the single butterfly!

2.4's

**WillySteve** · 03-11-2017, 08:25 PM

Ooops!!

**redsnapper386** · 03-12-2017, 03:24 PM

mx722 ihave same problem that just showed up,did head job still there. mine is 1993 carb 2.5 off shore fishin mtr. this is strange ,i seem to think maybe its a bad exaust plate gasket, some time with all motors you have to start a tear down and look for bad gaskets,my motor 1993 just started this after 24 years of service,not bad huh,i wanted to chime in here and share my prob,i will post later with results as i find it . cheers.