Snapped Belt

[JayG80]

I suggest a quick reread the other posts about alignment, free moving pulley, etc, good suggestions.

Here is how I installed my alternator belt on 2002 GT 40 Ski Nautique.

First loosen the lower bolt on the alternator, it has a nut on the backside that you will need to hold with a wrench. The bolt needs about a 9/16" wrench. I recall it takes a larger sized wrench than the top bolt will.

Next loosen the upper bolt - maybe 1/2" wrench. The attached photo shows the two bolt heads marked with masking tape to help visualize.

After the bolts are loose, slide the alternator toward the center of the boat. The alternator will pivot about the lower bolt and the upper bolt will slide along the slot in the alternator bracket.

Place the new belt on the two engine pulleys and press the belt onto the alternator pulley. This may take a bit of effort to work it around the pulley - so make sure the alternator is slid all the way to the end of the bracket.

Next find something to pry the alternator body out along the slide bracket to tension the belt. May use a prybar or pipe, just be careful what you place the end of the lever against.

(Don't worry about pulley alignment yet, wait until you have tightened the bolts.)

Pry the alternator toward the port side of the boat until the belt is tight.

Tighten the upper bolt while holding tension on the belt. Tighten lower bolt with another wrench on the nut as a backup or it will spin.

Check pulley alignment so that belt runs straight on all 3 pulleys.

Check the play in the belt by pushing down on the upper strand of the belt at a point midway between the alternator pulley and the circulating water pump pulley. The belt should depress 1/4". Adjust the tension by loosening the alternator mounting bolts and pivoting the alternator to obtain the correct tension.

After correct tension is set , tighten both of the bolts.

Now while you are at it - check the tension on the other belt for the raw water pump (impeller). Also see if it is worn. I like to replace both belts at the same time because you have to take the alternator belt off to access the raw water pump belt. Might save some work later on.

Check the belt tension by pushing down on the upper strand of the belt at a point midway between the raw water and circulation pump pulleys. This belt should also depress 1/4". If it depresses more than 1/4", adjust the tension by loosening the water pump mounting bolts and pivoting pump to obtain the correct tension. After the correct tension is set, tighten the bolts and verify belt alignment. Same procedure as used after changing the impeller.

[JayG80]

@DanielC, I did not see your post before I responded or I would have stopped typing.

I could not recall the recommended tension. I took that part of my post directly out of the Nautique owner's manual. But want to add - After I initially installed the belt fairly tight, there was an engine squeak so I did loosen the belt tension, there may be 1/2" play now.

[DanielC]

Don't worry about it. You are more detailed than me.

It is hard to get idea of what the recommended tension is. If you push lightly on the belt, a 1/4 inch of deflection may be OK. Same idea if you push really hard, 3/4 or even 1 inch of deflection may be OK. it is really a "feel" kind of thing. Hard to describe.

I have found the raw water pump belt does not need to be as tights at the alternator. The raw water pump pulley is about twice a big, so not only does the pulley have more leverage on the pump shaft, but the belt also has a lot more contact area.

I used to run the raw water pump belt tighter than I do now, but I had the bearings in the raw water pump give out. That is why I now run the belt looser.

[charlesml3]

Make sure that belt isn't melting instead of breaking. Yes, there's a difference. If the alternator is working way too hard it'll get really hot and eventually melt the belt. The alternator should be warm but not so hot you can't keep your hand on it. Check that if it breaks another belt.

If it's melting belts then try replacing the battery. If the battery is going bad the alternator may be pushing hard to keep it charged. If that doesn't fix it then most likely the voltage regulator in the alternator is going bad.

-Charles