"fan" belt squeal?

[frahkn]

I have two alternators on my Beta 43 and I think one of the belts is squealing but I'm not sure!

 

About ten seconds after I start the engine there is a loud squealing sound which stops if I rev the engine in neutral for a bit. This is new and getting worse - it now happens every time I start.

 

I am hoping that it is one of the belts (though they seem to have the usual 1 inch play). But I've started to worry that it may be something else, the bearing in the water pump for example. Is this likely?

 

 

[cheshire~rose]

We have been getting a similar thing on our recently acquired boat and it seems that it is because the batteries have got a bit low and the extra draw of trying to push charge into a low battery  bank is the cause, that is why it stops after a short time as the batteries settle into a steady charge

 

[Jen-in-Wellies]

If your boat isn't connected to a land line, then shortly after the engine starts is when both the engine and domestic alternators will be drawing the most power. The engine alternator to replace what you have just used to start the engine, the house alternator to recharge the domestic batteries, so this is when belt squeal is most likely. Also accelerating the alternators and water pump up to speed as you start is liable to make the belts slip, rather than in the steady state of running.

 

On my Beta 43, the house alternator is on a ribbed belt, the engine alternator and water pump on a V belt. If the V belt is worn, then it may be sitting on the bottom of the pulleys, rather than in the V grooves of the pulleys. This will reduce the contact area between belt and pulleys and make belt squeal more likely, even if the tension looks good.

 

What I'd do is remove the engine belt and see if the water pump and alternator pulleys can be turned easily by hand. This should show up any bearing problems in them. If OK, then I'd replace the V belt, set the tension and see if that makes a difference.

 

Jen

[bizzard]

To prove which belt is screaching just flick some water onto them whilst running. The screech will stop for a second or two which will tell you which belt it is. If it doesn't stop the screech its it'll be  something else.

[Tony Brooks]

As Jen says but where did this 1" play come from and what type of belt.

 

The normal method of assessing the tightens of a V belt is to apply moderate finger pressure in the centre of the longest run and expect 10mm of deflection. I suppose that if you are pushing the belt in and then pulling it out it would equate to a little under an inch movement in total.

 

If it is a large domestic alternator then it may be driven by a wide polly-V belt with loads of little Vs on the underside. Those should be adjusted with a belt tension gauge but a rough and ready way that is not approved of by the belt manufacturers is to tighten it until when  you try to twist the belt in the centre of the longest run you can only manage to twist it through about 90 degrees.

[BEngo]

Poly V belts should have a positive adjustment tension device, not just the "heave it tight and that will do" method commonly used with V and wedge belts-  a threaded adjuster is common.  With one of these, another way of tensioning a poly v belt without a gauge is to keep tightening up and trying until the belt squeal at start just dissapears.  Don't fanny about though as belt squeal causes rapid belt wear and if it is too worn you will never get enough tension on the belt to stop it squealing.

N

 

 

 

[Keeping Up]

My Beta manual recommends just 10mm of deflection when you press firmly at the midpoint of each belt's longest run with your thumb, ie on both the starter V-belt and the domestic poly-V.

 

I love the way that on my Beta 43 there is a big label on the domestic alternator bracket saying "Do not over-tension". I always wonder if it is meant to apply only to the belt or more generally to life as a whole.

[magpie patrick]

Ripple and Lutine both suffered with drive belt squeal - sooner or later the squeal would stop permanently when the drive belt snapped! It tends to be a sign the belt isn't quite as tight as it could be, and I guess that can also be a sign the belt is near the end of it's life. 

[mayalld]

5 minutes ago, magpie patrick said:

Ripple and Lutine both suffered with drive belt squeal - sooner or later the squeal would stop permanently when the drive belt snapped! It tends to be a sign the belt isn't quite as tight as it could be, and I guess that can also be a sign the belt is near the end of it's life. 

Daughter's boat suffers perpetual squeal, and destruction of belts.

 

It became almost a ritual - Start engine, belt squeals, stop engine, re-tension belt, start engine, all is well.

 

Belt alignment is perfect.

 

Then I discovered the issue - User error!

 

When he re-tensioned the belt, he tightened both the mounting bolts, and he tightened the slider bolt. He wasn't tightening the bolt that fastened the arm to the engine. The result was that over the course of the day, it was acting as a little hammer to slide the bolt along the slider.

 

[cuthound]

1 hour ago, Tony Brooks said:

As Jen says but where did this 1" play come from and what type of belt.

 

The normal method of assessing the tightens of a V belt is to apply moderate finger pressure in the centre of the longest run and expect 10mm of deflection. I suppose that if you are pushing the belt in and then pulling it out it would equate to a little under an inch movement in total.

 

If it is a large domestic alternator then it may be driven by a wide polly-V belt with loads of little Vs on the underside. Those should be adjusted with a belt tension gauge but a rough and ready way that is not approved of by the belt manufacturers is to tighten it until when  you try to twist the belt in the centre of the longest run you can only manage to twist it through about 90 degrees.

 

I have a Beta 43 with twin alternator and adjust in accordance with Tony's advice above.

 

I found the recommended V belt for the domestic alternator was actually slightly too long, leaving almost no adjustment on the adjuster whenever a new belt was fitted. Before long the belt stretches, (leaving tell take black belt powder marks on the alternator and swim), and the adjuster runs out of adjustment.

 

I bought a shorter, cogged V drive belt and that has cured the problem.

[Tony Brooks]

1 minute ago, cuthound said:

I bought a shorter, cogged V drive belt and that has cured the problem.

 

Yes, always use a  cogged belt for marine use because  it grips the typically smaller marine alternator pulleys better than an ordinary V belt. Does not apply to polly-V belts.

[frahkn]

Thanks everyone.

 

I had the engine moved over the winter and it now has a steel guard over the belts, this makes it a little difficult to measure deflection accurately.

 

I'll have to take it off and try the various suggestions.

 

Probably be back tomorrow.