[Magnolia Outdoors Guy]

It's time to buy an alternator for my fan. Both the motor and the stand should be finished this week. I'll be running a 45" 4-blade Ultra-Prop on a 25HP Kohler Command Pro 25 which idles 12 approximately 1200 rpm. It has the 6" pulley from Ultra-Prop on it. My DC charger will use only 45 amps at a time but I would like to see it charging at full capacity at idle or slightly above.

I've been Googling my butt off and so far I believe I need a high amperage low rpm 1 wire self exciting alternator. There's not a lot of charts available to show generated amps at certain rpms except on high dollar racing or marine models. I am thinking a 100 amp tractor alternator may do the trick but I would really like to benefit from the experience and knowledge I know some of you guys have using these things.

Also, do all alternators have ground wire connections?

Any information you guys can share would be appreciated and hopefully this thread could be one easily found in the future by others with the same question.

 

[Fullbore]

Ill sell you a new set up as i went to a genny, Front output shaft and pulley to run alternator to charge battery's. 140 amp alternator everything is brand new. with this ratio its 85 amps at idle and 140 amps at anything over 1200 rpms Bought for a 35 hp vanguard $200 plus shipping

this is the end result (not mine but how i was planning on doing it)

 

[Magnolia Outdoors Guy]

I believe 85 amps at idle is about double the amps my dc charger can utilize and I already have the pulley kit from Ultra-Prop. Is the front output shaft supposed to be universal? I get the benefits of putting the alternator on the opposite side of the fan blades themselves.

 

[On-fish]

What to you need all the DC amps to charge? Are you running DC LEDs?
Just curious.

 

[Magnolia Outdoors Guy]

I need to charge both 24V & 12V banks to operate LED lights & the other typical boat accessories. My DC charger will do that. It just needs a charging source.

 

[THS Tim]

Todd you have put together the perfect boat. I believe I might just start on putting on together this fall. Why the 25 hp motor and not something a little bigger?

 

[Magnolia Outdoors Guy]

I already had the motor from a 6x6 with a blown transmission that had been sitting up for some years.