96f350psd

So, if the Delco does not charge until 1200 rpms (like what mine is doing) would installing a smaller pully like CDOG suggested help or should I do something different?

CN24

Yes ,there is only one wire. So I take it it's working OK.

Steve H

Marine alternators are not sealed. They are open inside to allow the fan to circulate air through them. Otherwise they would overheat and die in short order. The only difference from a automotive unit is that thay are U.L. approved. They will not cause ignition of fuel vapors under laboratory conditions. Some units such as older delco use screens because a spark will not go through a screen. Others such as Mando and Prestolite will seal the brush holder assy from the atmosphere because this is the most likely place for a spark to originate. Then others such as after market high output units don,t even do this. They custom fit the brushes and precision turn and balance the rotor eliminating brush bounce wich in turn stopping any arcing

Steve H

Edward R. Cozzi

I have found it is not unusual for a Delco one-wire (self-exciting) alternator to need a slight rev-up to start things up. Once the regulator is kicked-in, you can go back to idle and still be charging.
I would be careful with smaller pulleys as you may be spinning the alternator too fast for the bearings at running speeds.
A fully charged, healthy battery should read about 12.8 volts. Start the engine and watch the on-dash volt meter. If after a small rev-up it reads 13 or more, chances are the charging system is fine.
Remember: with an alternator it takes voltage to make voltage, so make sure the connections are clean and secure. If you can turn the alternator with your finger (engine OFF, of course!), the belt is too loose.

CN24

I understand the screen keeping sparks in, but what keeps fumes out?

Edward R. Cozzi

I suppose the cooling fan that's either inside or behind the pulley on the outside.

happy hours

I have a Volvo Penta and am unsure who makes the alt. but it does not charge until it reaches about 1500 rpm for the first time to "energize " it. Then it works perfectly from a voltage regulation standpoint even at like 600 rpm. Only issue is the electric fuel pump gets it 12 volts from the charge circuit (and starter start circuit). So if you start the boat and never rev it ....eventually it will run out of fuel. Is there something wrong with the alt"?

Edward R. Cozzi

No, just remember to get the regulator involved once you have oil pressure.