2005 5.7 Horizon with whine noise

[Bronik290]

I'm experiencing a whining noise sound in my 2005 320 Sundancer which varies with RPM from both engines that begins at about 900 rpm and continues to 1300 rpm. The noise will only occur while operating in a 5 MPH zone, won't happen in neutral, won't happen when tied to the dock, and won't happen with 1 engine in reverse and 1 in forward.

I have changes all of the idler pulleys, replaced both belts with Mercruiser belts, had both raw water pumps serviced, even replaced one alternator with a brand new mercruiser part. The belt alignment is spot on. The batteries are less than 1 year old and have been successfully load tested. IAC mufflers replaced. My mechanic is a certified Merc tech took a ride and used a stethoscope and the noise directed him towards alternator issue, but that was ruled out after the new Merc Alternator was installed. He unplugged the new alternator to see if the load was the issue with no change in the whine.

My Merc tech reached out to 3 other Merc techs and none of them has ever had this issue.

AND last season had the starboard V drive removed, serviced and reinstalled with a brand new Merc coupler.

Other than the noise, the boat runs great, all gauges look great, even at 4500 WOT.

Any insight on the cause of this annoying noise would be helpful

 

[CliffA]

My mechanic is a certified Merc tech took a ride and used a stethoscope and the noise directed him towards alternator issue, but that was ruled out after the new Merc Alternator was installed. He unplugged the new alternator to see if the load was the issue with no change in the whine

that was an expensive missed diagnosis.....

are you sure the sound is coming from both engines?....have you run one engine at a time to verify this?....

if both engines are making the sound it is likely from something in common to both engines....

cliff

 

[sdleo26]

I have the same issue but only in port motor; it's more of a whistle than a whine however. I believe it is a harmonic ; at least that's what I convinced myself it is.

It's been like this for 6 years and while it still drives me crazy, it is only present between 950 a 1250 RPM... You would like to think that if it was something wearing, you would hear it at other RPM ranges.

 

[CliffA]

I have the same issue but only in port motor; it's more of a whistle than a whine however. I believe it is a harmonic ; at least that's what I convinced myself it is.

It's been like this for 6 years and while it still drives me crazy, it is only present between 950 a 1250 RPM... You would like to think that if it was something wearing, you would hear it at other RPM ranges.

my 6.2's also whistle at a low rpm just slightly off idle....the whistle goes away after the rpm's are increased to around 1500 or so...if this is the sound the OP is hearing I think it is normal....I think it has something to do with the velocity of the air being sucked into the engine at that rpm that creates a harmonic whistle....

cliff

 

[Partyoffive]

Are you sure it's not the IAC mufflers? From what I've been told this is the sole purpose of the IAC muffler??

 

[skibum]

Are you sure it's not the IAC mufflers? From what I've been told this is the sole purpose of the IAC muffler??

I was thinking that I had read a thread about that a long time ago on here.

 

[SeaAyeOwe]

I had a similar whine on one of my motors when I first bought it at low revs - in my case the problem was the air filter box - it had some damage on the rim where it had been fitted onto the engine and sow as not seated correctly - as soon as I fitted it properly the problem went away.

 

[CliffA]

Are you sure it's not the IAC mufflers? From what I've been told this is the sole purpose of the IAC muffler??

as far as i can tell there are no mufflers on the IAC valves on my engines....I have replaced both IAC valves which looked to be original and found no muffler in either valve.....here is a pic of the IAC valve on my engines....

maybe a muffler is supposed to be there but I did not see where it would go and did not see one on the parts diagram when I ordered the new IAC valves......

cliff

 

[CliffA]

I had a similar whine on one of my motors when I first bought it at low revs - in my case the problem was the air filter box - it had some damage on the rim where it had been fitted onto the engine and sow as not seated correctly - as soon as I fitted it properly the problem went away.

thanks for that.....I will check my flame arrestors this WE to insure they are seating properly.....

cliff

 

[Bronik290]

I did install new IAC mufflers last year as well, and test ran both engines in all types of scenarios with no change in the whining sound. The sound coming from the IAC mufflers (a sucking air flow sound) is not the same as the sound I'm experiencing.

 

[sdleo26]

thanks for that.....I will check my flame arrestors this WE to insure they are seating properly.....

cliff

Cliff the little white sponge filters, which are more than likely black now in your case, would be underneath the flame arrester on the side of the throttle body housing where the hose inlet feeds your IAC. They are not in the valve itself.

You should change these every year as my understanding is that dirty ones help promote blown IAC's

 

[CliffA]

Cliff the little white sponge filters, which are more than likely black now in your case, would be underneath the flame arrester on the side of the throttle body housing where the hose inlet feeds your IAC. They are not in the valve itself.

You should change these every year as my understanding is that dirty ones help promote blown IAC's

got it.....thanks....

cliff