BMC Charging and Alternators

[dmr]

Here at Middlewich and trying to help a fellow trader (and full time off grid CCer) with charging problems, I don't have much hands on experience with BMCs so a bit of help from an expert (Tony?) would be good.

Its a 1.5l engine with a 70 amp alternator. The owner needs to run a fridge and freezer so its all very marginal. Alternator has a 10mm belt. We have got the alignment okish but still not quite perfect. At any more than about 35 to 40amps the belt is very gently smoking. Is 40amps the practical limit for a 10mm belt?

Does anybody do a kit of pulleys for a reasonable price to go up to 13mm?

Is it viable to install a second alternator? Is there a ready made kit of alternator and pulleys/brackets to do this, again not too expensive? Or is two alternators just too much for an old 1.5l BMC?

There is noticeable play in the waterpump, is this normal, slightly concerning or very bad? Otherwise engine sounds rather nice and electrical installation looks reasonable.

We have already decided that some solar would really help, though more engine charging would be good for the winter.

Currently three cheapo leisures batteries and minimal instrumentation. Money is tight and access limited so I think staying with cheapo maintenance free batteries is the best option. Will check charging voltage later, still in bulk mode right now.

...........Dave

 

 

[Tony Brooks]

Water pump all but certainly on the way out unless its a Jabsco and if it is expect priming problems.  This suggests it may have been a long term problem problem and the belt has been run over tight for some time.

With matched pulleys and belt you should get away with about 90 amps so I suggest you may have mismatched pulleys  and belt OR is the belt too slack? I suppose it is even possible the water pump is seizing when hot but they usually leak.

I suspect the wrong profile belt. Maybe it is a V belt but needs a wedge or vis a versa. Whichever it is supposed to be always choose the notched or cogged version, it helps go around and grip  out typically small alternator pulleys. (google belt profiles).

Take the belt off, twist it inside out and push it into each pulley in turn.

If it touches the bottom of the pulley its either badly worn or the wrong belt for that pulley. You should see clear daylight under the pulley.

The belt sides and pulley sides should be absolutely parallel, it not then its the wrong belt for that pulley.

The top of the belt should not be more than a little proud or below the pulley rim. If it is then the belt is probably wrong but they can ride low in the water pump if the other two are OK.

As the engine pulley is also a torsional oscillation damper I doubt that you can get parts to fit a 13mm belt.

As far as fittings for a second alternator I suggest the only chance for ready made is Calcutt Boats unless Richard has done anything.

 

 

 

[RLWP]

Not needed to, Tony. Our alternator keeps up with our demands. I do find it hard to work out the correct length though, there doesn't seem to be a lot of adjustment to take up wear

Richard

[Tony Brooks]

I just wondered it you had taken on fabricating parts to fit a second alternator, that's all. If Calcutt can't help I fear it will need the engine pulley boss modifying and  anew centre bolt making.

FWIW some BMCs have an extra pulley on the engine pulley to drive a belt driven Jabsco but I think it would be way too small. I can't remember how this extra pulley got positive drive.

[ditchcrawler]

I think the second alternator came up some time back and the answer was no kit for a 1.5 BMC only 1.8

Been a few threads 

https://groups.google.com/forum/#!topic/uk.rec.waterways/6mL0k_0GLZ0

Edited June 20, 2017 by ditchcrawler

[Tony Brooks]

So do I.

[dmr]

56 minutes ago, Tony Brooks said:

Water pump all but certainly on the way out unless its a Jabsco and if it is expect priming problems.  This suggests it may have been a long term problem problem and the belt has been run over tight for some time.

With matched pulleys and belt you should get away with about 90 amps so I suggest you may have mismatched pulleys  and belt OR is the belt too slack? I suppose it is even possible the water pump is seizing when hot but they usually leak.

I suspect the wrong profile belt. Maybe it is a V belt but needs a wedge or vis a versa. Whichever it is supposed to be always choose the notched or cogged version, it helps go around and grip  out typically small alternator pulleys. (google belt profiles).

Take the belt off, twist it inside out and push it into each pulley in turn.

If it touches the bottom of the pulley its either badly worn or the wrong belt for that pulley. You should see clear daylight under the pulley.

The belt sides and pulley sides should be absolutely parallel, it not then its the wrong belt for that pulley.

The top of the belt should not be more than a little proud or below the pulley rim. If it is then the belt is probably wrong but they can ride low in the water pump if the other two are OK.

As the engine pulley is also a torsional oscillation damper I doubt that you can get parts to fit a 13mm belt.

As far as fittings for a second alternator I suggest the only chance for ready made is Calcutt Boats unless Richard has done anything.

 

 

 

Thanks, that makes sense, owner has recently changed the alternator pulley, I think it was a 13mm pulley (or otherwise wrong) and the belt was bottoming out, the belt looks like a wedge, has very little depth, so maybe this was fitted to try to cure this problem, suspect it could now maybe take a notched V belt, hard to tell, very little access to the engine pulley. As someone used to a clean engine in a clean engine room I find old cruiser stern engine spaces very dark and dirty .

Will have another look this evening.

............Dave