Alternator Pulley Selection Guide
The standard diameter pulley for Balmar alternators is 2.7". While
all Balmar high-output marine alternators are rated for much higher
speeds, the ideal sustained operating range is 4000-4500 RPM.
Divide your crankshaft pulley diameter by the alternator pulley
diameter to get the speed ratio. Multiply this by the engine's cruising
RPM to get the alternator RPM.
5.0" ÷ 2.7" = 1.85 (Speed Ratio)
- Engine crankshaft pulley diameter: 5.0"
- Alternator pulley diameter: 2.7"
- Engine cruising RPM: 2400
1.85 x 2400 RPM = 4440 RPM (Alternator)
If your engine is typically run at low speeds, or if it has a small crankshaft pulley,
select a smaller alternator pulley.
CAUTION: Use of an undersized pulley may cause the alternator
to exceed its RPM rating when the engine is run at wide-open throttle
(WOT). Use the formula above to determine the alternator RPM at max
Note: Certain marine engine applications have specific pulley
requirements, and other pulleys are available. We have attempted to
make the selection as easy as possible for you, and the selections
provided will fit most engine applications.