• If you log in, the ads disappear in the forum and gallery. If you need help logging in or getting registered, send request to: webmaster@southernairboat.com

350dd and march underdrive pulleys

D

Dying_breed

Well-known member
I picked up a set of march underdrive pulleys. For a smokin deal. My stock crank pulley had a slight wobble it that bothered me.. I threw the new pulleys on, they look great. I know shiney shit dont mean a darn thing and chrome dont get ya home... But will see any negative effects by running these? I dont idle alot. I cruise around 2k rpm and wot is 2850 ... So will the slower rpm from the pulley swap hurt me? Thanks for any insight and comments in advance. And yes i searched for it...
 
An under drive system turns the accessories slower. It does that to reduce parasitic drag and free up power. It's a very small amount on an airboat engine as typically we only run a single belt, alternator and water pump.

The concern or thing to watch in initial testing is that an under drive will turn the water pump slower so some engines after running hard and going to idle will get hot.

That is why you see some folks use the electric water pump. It uses no power and moves water through at a faster rate regardless of engine rpm.




dodobird said:
I did the under drive pulley bc alternator dont like to charge at low rpms n when I'm frogging I just idle around so I figured it would turn it faster n charge which it does 20190413_174233.jpeg

Sent from my SM-G960U using Southern Airboat mobile app powered by Tapatalk
Click to expand...

DoDo if your running a GM 7127 or similar there are some that just "excite" earlier than others. I have had them where they needed 1400 plus and others that would produce 14v at a low idle. There are some aftermarket units being sold by Advance for around $45 that really produce well at slow speed. We have one on the boat now and it is in a true 10% under drive.
 
Under drive means to slow the rotation of a system. The objective is to "under" low speed the accessories.

That is done to reduce the parasitic drag.

Typically a smaller crank pulley is utilized often in concert with larger accessory pulleys.

https://en.m.wikipedia.org/wiki/Underdrive_pulleys
 
Could you have one of the alternators I was talking about?

Mine is the single wire GM version. It is made by some aftermarket company probably foreign built. The only thing odd is the standard belt width appears a bit to thick for the width of their pulley. It works ok but the belt doesn't drop down into it fully it sits up just a touch. If yours is doing that maybe this helps explain how you can under drive an get excellent charging. My crank pulley is a billet custom and is apx a 10% under drive. My old alternator would really need rpm to wake it up and keep it at 14v. This new one is a rockstar it wakes up at idle and gives a 14v+ output nearly at any rpm if the engines running.

Slide safe brother
 
You must log in or register to reply here.
Back
Top