Boat altenators

[juruca]

Small question: why do boat alternaters not have a idler pulley like in cars ?
Thanks!

 

[bbook83]

My 5. 7 L has two idlers, per the attached diagram.

 

[matt167]

Old cars often had no idler pulley with v belt systems. The alternator was the adjustment point. Many older boats use v belts. Serpentine systems use idlers and tensioners and only sometimes is the alternator an adjustment point. Most modern boats have serpentine systems

 

[Fun Times]

Small question: why do boat alternaters not have a idler pulley like in cars ?
Thanks!

Sort of depends on what engine model/year you have that utilizes a serpentine belt design such as this one on a Merc engine item number 15, https://www.mercruiserparts.com/bam/subassembly/31857/13967/20

Or are thinking of the self-adjusting tensioner design some cars may use.

 

[juruca]

thanks for your replies but i think i got the wrong translation for the pulley off the alternator.

I mean the pully of the altenator: why in boats the altenator not have freewheel clutch.
That mean clockwise rotation the alternator will be driven but counter clockwise rotation the alternator is not driven.

i hope its clear...

 

[racerone]

???---Any pictures of your set up ?

 

[juruca]

Sorry they call it O.A.P. Overrunning Alternator Pulley.

Hope this will make clear...

 

[Scott Danforth]

thanks for your replies but i think i got the wrong translation for the pulley off the alternator.

I mean the pully of the altenator: why in boats the altenator not have freewheel clutch.
That mean clockwise rotation the alternator will be driven but counter clockwise rotation the alternator is not driven.

i hope its clear...

the sprag clutch on SOME performance car alternators are there if you have a manual transmission and the motor sees many RPM changes in a short period of time. for example, my turbo charged daily driver has a sprag clutch on it (and it has failed twice). the purpose is to not throw a belt when rapidly shifting gears and your RPM's go from 6500 to 4000 with ever shift by allowing the motor to slow down faster than the alternator would and not back-driving the belt.

95%-97% of alternators in the world do NOT have a sprag clutch front pulley. its not needed on vehicles with automatic transmissions, its not needed on heavy equipment and its not needed on boats

Additionally, boats would never need a sprag clutch as they have one gear and the RPM will never change enough to ever need one. additionally when they fail, they can cause sparks

alternators will produce power if turned in either direction.