What a timely topic! Everybody wants more power, including me. OK, well maybe not the Pardeys.
The slight delay (1 minute in most Balmar regulators) before coming online with the field current is not to prevent "shock loading" of the belt. It is to allow a freshly started engine to get its lubricating oil into all the oil passages. This is to prevent unnecessary wear on internal engine parts and to make sure the engine is ticking over nicely before putting a load on it. Plus one for Balmar.
There's a feature in the (Balmar) regulator which can reduce the maximum load on the belt by reducing the maximum field current in the alternator. Sorry I haven't got the manual in front of me. It's one of the extended menu optons. I had to do this to keep my belts from burning up when I got a new 110 amp Balmar. That model also came with a single pulley.
There are a few other things you might think about:
1) Have you changed the charging system in any way? New inverter/charger?
2) Did you change marinas? and is there a difference in the power available?
3) Are your batteries fully topped when you leave home port? If your alternator is running full tilt right out of the gate you run a lot higher chance of burnout.
4) Are you doing more overnighters? Charging at anchor more than you used to? That's usually when I have problems. The batteries are down and they want all the current the alternator can deliver. I have AGM batteries and they would accept several hundred amps if my alternator could deliver it.
If you want to pursue the two belt system, you may have to take the crank pulley off the engine and take it to a decent mechanic or machinist. Get an identical pulley and join the two together (weld or bolt or both) so that they have exactly the same center of rotation. Make sure you still have access to the mounting holes and hardware to get the rig back on the engine. To keep the belts equally tensioned you may have to do the same thing with the raw water pump pulley. Then there's the alternator to deal with.
I just had a thought: ... When asserting that only one belt is required, Balmar probably assumes that there is no other load on the belt and that there is a nearly 180 degree engagement with the pulley. Neither of these is true in my installation because of the raw water pump pulley. The RW pump doesn't pull much power, but it certainly prevents getting a good wrap of belt around the alternator pulley. I get maybe 120 degrees.
Mike's advice offers a good alternative to the two belt system: A larger size pulley gives the belt more area to bite plus greater mechanical advantage. As Mike points out, there will be less output at low RPM, but even at moderate RPM these Balmar alternators should be able to achieve full current ouput. Check out the ouput curves on the Balmar site:
http://www.balmar.net/Page3-Smallcasealts.html
These alternators achieve nearly full output at about 2000RPM (that's alternator RPM). With the standard size pulleys that's about 800 RPM for my 3QM30FG. A slight increase in pulley diameter could be exactly what you want, if it keeps your belt from slipping. Charging at idle would be a little slower, but charging while under way would be at full power output.
How you handle it depends on your cruising profile.
-The quick fix is to limit the output via the regulator. Saves belts and aggravation.
-The middle fix is the larger alt pulley, if you charge under way or don't mind somewhat reduced output at idle. [I like this one a lot.]
-The full fix is a dual belt or serpentine belt system. Full power, but a PIA to realize it.
Good luck!
