Perkins 4-108 : installation of 24V 60A Alternator.

[coopec]

The Perkins 4-108 is rated at 51 hp at 4000 rpm (intermittent) and 39 hp at 3000 rpm (continuous).
I really don't want to run the motor at that speed so I was thinking I'd cruise at around 2000- 2400 rpm. Maybe that is a mistake? (The expert who supplied the propeller worked on 3000 rpm cruising)

I am in the middle of installing a 24V 60A alternator and have found I can bolt a duplex "V" belt pulley to the existing (5½ in. diam) pulley on the crankshaft. (There are 3 holes already machined into the pulley). The existing (single V) pulley would be retained to work the water pump (I'll have to make up a tensioner)

Now the question is what diameter Duplex pulley should I bolt to the crank shaft pulley?

The existing ratio of crank shaft pulley to alternator pulley is 5½ in. to 3½: Should I maintain the same ratio with the 24V alternator?

It just so happens that the 12V alternator has the same diameter pulley as the 24V pulley so do I bolt a 5½ in duplex pulley to the existing crankshaft pulley?

Would there be any advantage in going bigger/smaller? Can anyone please advise?



Clive

 

[PaulRainbow]

Look up the output curve for the alternator, match the best output to the engine RPM

 

[coopec]

Have yet to find the output curve for my Toyota Coaster Bus alternator but looking at alternators generally they need to be spun at 3500-4000 RPM to get good output

https://www.google.com.au/search?q=...UICigB&biw=1280&bih=537#imgrc=59_6qq_GuS0KnM:

2000 engine RPM = 3142 alternator RPM. So that existing ratio looks pretty good.

Thanks

Clive

 

[geem]

If you look up the alternator for the Perkins M92b. It's a current Perkins Sabre 86hp engine. They do a 24v 60 amp alternator. Brand new from a Perkins dealer mine was £105. They are designed for an engine that revs to 2400 rpm and use a single belt. If you are interested PM your email address and I will email you power curve for the alternator.