High Pitch Noise from Engine?

[Klipper]

I have an 07 Outback that is fairly new and was wondering if any of you have experienced a high pitch noise from the engine (or engine area) between 2,500 and 3,000 RPM? Below 2,500 or above 3,000 it goes away.

Any ideas?

Thanks.

[cgriebs]

I get that high pitch noise on occasion in my '06 LS. I figured it was the hose that crossed in front of the alternator, which is only 1mm or two away from the pulley iteslf. The hard protective sleeve on the hose is actually getting sliced by the alternator pulley, albeit very slightly. Last year, I loosened the clamp and twisted the hose to allow for more clearance, and if I remember correctly, the noise went away. This year I forgot to twist it when I re-installed my hoses post-winter, and I have heard the noise again a few times already. Perhaps it could be the belt?

I have heard that the fuel pump could actually make a rather high pitched noise on occasion. Search and perhaps you'll find something on this issue as well?

[Klipper]

I checked it but it does not seem to be the issue.

Any other ideas?

[02Outback]

Check your impeller. Mine made the same noise..checked the impeller and sure enough, it was chewed up.

Are you overheating at all? Anything over 180+?

[Klipper]

Not overheating at all, i'm consistently at 180, engine has under 20hrs on it so the impeller should be fine unless i chewed some thing up.

[Klipper]

Ok,

Impeller is fine. Any other ideas of what could be causing this noise?? It's driving me nuts. It only happens between 2,500 and 3,000 rpm, only when i'm actually running on the water. It does not happen when I rev the engine at a stand still. It seems like it might be vibration related. I dont know....

Any ideas please!!

[gcnettl]

If it is a direct drive then drive with the hood off. If not then have someone drive it for you while you have the engine cover lifted to try and locate the noise.

[walb0244]

I would think since it only does it when on the water and not when you just rev the engine that it would have to be either the tranny or something around that area. Maybe a vdrive if it is a vdrive.

[Klipper]

I ran it with the cover off and the floor out. Sounds like it may be the belt! Very hard to guage where the noise is coming from but I think its the front of the engine.

Maybe it just needs to be tightened? Easy to do? Anyone had this problem after 20 hrs? Is this normal?

Let me know what you guys think.

Thanks.

[gcnettl]

If you can turn your water pump or alternator by hand then your belt needs to be tightened. There is also a lubricant spray that you can get at auto parts stores called "belt dressing" that will quieten no noisy belts.


I dont really understand why it only does it with the engine loaded. My f-150 does the same thing around that RPM range while driving, can not re create while I am setting still. It has done it for as long as I have had it, three years now.

[Klipper]

How do I tighten the belt? I can try that to see if it fixes the problem. Also, is belt dressing a good solution for a sweeky belt or should i be changing it?

[gcnettl]

I dont think you have a spring tensioner on your belt do you? On my boat you loosen the alternator bolts, there are two. One threads into the motor and the other to this adjustment arm. The arm also a bolt that holds it to the motor. So loosen the three bolts, using a pry bar pry the alternator outward so as to put tension on the belt, then tighten the bolt on the adjustment arm/alternator while holding tension. Then tighten the remaining two bolts.


Some times pulleys are a little out of alignment. This causes belts to sit in the pulley just a little off, and the side of the belt rubs the inside of the pulley. Unless you can see it with your eye by looking down the belt and noticing it out of alignment, then it is not off much. The belt dressing acts a rubber conditioner, thereby reducing the friction.

I would not replace a belt unless it looks worn, has cracks, shows the cord, etc. If you decide you want to tighten, tighten just enough to keep from being able to spin over the alternator or water pump by hand.

The next time I went to take my boat out I would just carry one of those cans along, fire it up and spray a little on the belt, and if that cures the problem, I would either use it every now and again or buy a good belt.

[Engine Nut]

How do I tighten the belt? I can try that to see if it fixes the problem. Also, is belt dressing a good solution for a sweeky belt or should i be changing it?

It is probably not the belt but you can verify it by taking the belt off and taking the boat out and run it at the RPM where the noise occurrs. Running for a few minutes without the belt isn't going to hurt anything. I suspect the noise you are hearing is caused by air blowing across the throttle plate... kind of like blowing across the top of a soda bottle. Unfortunately there isn't much you can do if that is the issue. Sometimes there is a burr on the edge of the throttleplate that can be "softened" with abrasive paper or a fine file but this is a job better left to an expert.The noise doesn't hurt anything except annoy.

[gcnettl]

I would not run my boat with the belt off. Might would be ok if you didnt have to put in the water, get out to cruising water, and then get to cruising speed, then bring it back in, load it. But anything over a minute or so is too much.

[Klipper]

The noise only happens when I'm runnig in the water at speed. It does not happen when at a stand still with the engine revving at 2,500. Therefore, it seems like it could be the throttle plate.

Is there a way to test this?

[gcnettl]

Air movement by the throttle plate would be the same whether the engine is loaded or not.

[Klipper]

it only happens loaded, when i'm between 2,500 - 3,000 RPM's anything above or below that, there is no noise.

[JesseC]

Air movement by the throttle plate would be the same whether the engine is loaded or not.

I don't know if I agree with this one, under a no load and the engine running 3,000 rpm is way different than a boat with a load running 3,000 rpm. More fuel and air will be required to sustain the 3,000 rpm. Since your boat is a Direct Drive, I would take Larrys suggestion from above and only run for a few minutes to check the issue. Just watch your temps. A simple remove the belt, start the engine run past the problem range, then shutdown and replace the belt will not hurt anything. Larry is from Indmar engines and would nto put out a suggestion that would hurt our boats. By doing this test it would eliminate anything that is belt driven as well as the belt itself. SInce you will have the belt off, go ahead and replace it with a new one and keep the old one as a backup.

[Klipper]

Looks like Enginenut is correct.

I just took the boat out again and took the flame arrestor off and had a listen. It is air going through the throttle plate!!

I dont know why it only happend when the engine is in gear and not in neutral but that is what it is.

Thanks Enginenut for your expertise on this. If there is a way to get it to go away, let me know, otherwise, i can live with it.

[gcnettl]

Hats off to you enginenut. Have not heard of this one before.

[cgriebs]

EngineNut is a Indmar employee. Listen to him as I'm sure he's offering worth while advice when he chimes in :)