I have noticed a couple times I get a build up of black dust under the motor in the bilge. The belts don't look they are warn too bad and I don't see where any hoses or belts are rubbing. I check on the motor a lot while running, and never smell burning rubber.

What can this be coming from or is there other things I should be checking?

Tough to get a good shot of the dust:


dean

My belts never look real worn, but I do get a fair amount of belt dust.

Drive coupler and belts are the only moving rubber parts i can think of.

Are your pullies rusted?
Are they tensioned enough?

I replaced some of mine with aluminum and glass beaded then repainted the rest. Then paid strict attention during reassembly with a straight edge. Make sure they all spin true... Just an hour cleaning them with a wire brush and sometimes realigning the alternator makes this go away.

Make sure you check for wobbly pulleys indicating worn bearings in circ pump , alt etc etc .

+1 for coupler !

+1 but polished rusty pulleys will cause it..

every time i have noticed that black dust i have lost a belt within a few hours, even after looking at the belts, and they looked ok.

later

Thanks Guys. I was expecting the coupler or the belts. I took a look at the engine tonight and I see that my alt belt does seem a little loose. I also pulled the water pump and I'm seeing some grooving in the pulley:



I'm wondering if this is the cause of the dust. Looks like I'm at least due to pull all they pulleys and clean/re-aline with new belts this winter.

Is there any way to check the coupler? I know it involves pulling the motor to replace, which i would rather do in the 8 months we have off if needed....

Thanks for all the help.
Dean