Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 21-05-2015, 12:36   #1
Registered User
 
thebootlegger's Avatar

Join Date: Oct 2013
Location: Slidell, La.
Boat: Halmatic Nelson 40
Posts: 132
Alternator for a Perkins 4-108

I need to find out what the largest belt driven alternator is that I can put on my Perkins 4-108. Thanks


Sent from my iPhone using Cruisers Sailing Forum
__________________

__________________
thebootlegger is offline   Reply With Quote
Old 21-05-2015, 12:51   #2
Registered User

Join Date: Oct 2008
Posts: 205
Re: Alternator for a Perkins 4-108

I have a 85 amp alt with a single belt. Anything larger probably requires a double belt. Bob
__________________

__________________
roberttigar is offline   Reply With Quote
Old 21-05-2015, 12:55   #3
Registered User
 
FastCruiser's Avatar

Join Date: Apr 2015
Posts: 54
Re: Alternator for a Perkins 4-108

I had a 130 from cruising specialities but it was dated 30 years ago.. went with the new Balmar 6 series with a smart charger.. works great..
__________________
FastCruiser is offline   Reply With Quote
Old 21-05-2015, 13:03   #4
Registered User
 
Stu Jackson's Avatar

Join Date: Jan 2011
Location: Cowichan Bay, BC (Maple Bay Marina)
Posts: 6,389
Re: Alternator for a Perkins 4-108

I have a 21 hp engine, single belt, 100A alternator. That's where the external regulator shines: then you MANAGE the belt load (to avoid belt slippage). Heck, ya could put a 200A alternator on that engine.

And, the MAX output of the alternator is determined by the SOC and size of your house bank.

Then you manage the load with the regulator. Pretty full bank after one night: either use the small engine mode I described or de-tune the alternator always with amp manager. It is a PITA to re-program all the time, so if you use amp manager you're always de-rating the output. Which I find is counter-productive, others use it all the time. All covered in my links.

Good luck.
__________________
Stu Jackson
Catalina 34 #224 (1986) C34IA Secretary
Cowichan Bay, BC, (Maple Bay Marina) SR/FK, M25, Rocna 10 (22#) (NZ model)
Stu Jackson is offline   Reply With Quote
Old 21-05-2015, 13:16   #5
Senior Cruiser

Cruisers Forum Supporter

Join Date: Jul 2006
Location: Chesapeake Region and Maine
Boat: 42' Bob Perry sloop
Posts: 4,038
Images: 4
Re: Alternator for a Perkins 4-108

To directly answer the OP's question:

You can easily drive up to a 100-amp alternator with the 1/2" belt on a Perkins 4-108. I've had a Balmar 100A alternator on mine for 14 years.

Two things:

1. With a good external regulator -- like the Balmar MC-612 or 614 -- you can de-rate the alternator's output to any desired level. For example, you can de-rate a 100A alternator to 80A or 70A or anything you like. Using this feature, you could mount a very large output alternator, and de-rate it to no more than 100A and you'd be fine. There might even be some advantage in doing this, particularly with AGM and gelled batteries which have a higher acceptance rate than FLAs; and

2. You must be very careful to align the alternator pulley with the drive pulley and the water pump pulley. Any misalignment will quickly lead to excessive belt wear, belt "dust", etc.

Bill
__________________
btrayfors is offline   Reply With Quote
Old 21-05-2015, 13:34   #6
Guy
Registered User

Join Date: Feb 2013
Location: So. Oregon, USA
Boat: Seafarer36c
Posts: 4,308
Re: Alternator for a Perkins 4-108

How do you align a pulley? It seems like the only thing you could align is an alternator that has a lot of slop in the large mounting hole. The alternator mount on the engine is pretty solid, so no adjustment there.
__________________
Guy is offline   Reply With Quote
Old 21-05-2015, 13:46   #7
Senior Cruiser

Cruisers Forum Supporter

Join Date: Jul 2006
Location: Chesapeake Region and Maine
Boat: 42' Bob Perry sloop
Posts: 4,038
Images: 4
Re: Alternator for a Perkins 4-108

Quote:
Originally Posted by Guy View Post
How do you align a pulley? It seems like the only thing you could align is an alternator that has a lot of slop in the large mounting hole. The alternator mount on the engine is pretty solid, so no adjustment there.

http://www.gates.com/~/media/Files/G...0Alignment.pdf
__________________
btrayfors is offline   Reply With Quote
Old 21-05-2015, 14:47   #8
Guy
Registered User

Join Date: Feb 2013
Location: So. Oregon, USA
Boat: Seafarer36c
Posts: 4,308
Re: Alternator for a Perkins 4-108

Quote:
Originally Posted by btrayfors View Post
That's nice but it does not tell you how to change the alignment.
__________________
Guy is offline   Reply With Quote
Old 21-05-2015, 14:53   #9
Senior Cruiser

Cruisers Forum Supporter

Join Date: Jul 2006
Location: Chesapeake Region and Maine
Boat: 42' Bob Perry sloop
Posts: 4,038
Images: 4
Re: Alternator for a Perkins 4-108

Pulley adjustment on shaft, shims, mount adjustment. If you need more, get a qualified engine mechanic or machinist.
__________________
btrayfors is offline   Reply With Quote
Old 21-05-2015, 15:19   #10
Registered User
 
thebootlegger's Avatar

Join Date: Oct 2013
Location: Slidell, La.
Boat: Halmatic Nelson 40
Posts: 132
Re: Alternator for a Perkins 4-108

Thanks so much for the good information.
__________________
thebootlegger is offline   Reply With Quote
Old 21-05-2015, 15:19   #11
Registered User
 
Stu Jackson's Avatar

Join Date: Jan 2011
Location: Cowichan Bay, BC (Maple Bay Marina)
Posts: 6,389
Re: Alternator for a Perkins 4-108

Quote:
Originally Posted by Guy View Post
How do you align a pulley? It seems like the only thing you could align is an alternator that has a lot of slop in the large mounting hole. The alternator mount on the engine is pretty solid, so no adjustment there.
Guy, all engines, of course, are different, but here's how we do ours. Also scroll up to reply #33 about using the right bolts.

CRITICAL UPGRADES - DO THESE OR ELSE!!!
__________________
Stu Jackson
Catalina 34 #224 (1986) C34IA Secretary
Cowichan Bay, BC, (Maple Bay Marina) SR/FK, M25, Rocna 10 (22#) (NZ model)
Stu Jackson is offline   Reply With Quote
Old 21-05-2015, 17:08   #12
Registered User
 
leftbrainstuff's Avatar

Join Date: May 2011
Location: San Francisco and Australia
Boat: Liberty 458
Posts: 1,979
Re: Alternator for a Perkins 4-108

Quote:
Originally Posted by thebootlegger View Post
I need to find out what the largest belt driven alternator is that I can put on my Perkins 4-108. Thanks


Sent from my iPhone using Cruisers Sailing Forum
Once you start pushing over 90A you'll want to consider dual v belt or similar.

Sent from my SM-N900T using Cruisers Sailing Forum mobile app
__________________
leftbrainstuff is offline   Reply With Quote
Old 21-05-2015, 17:41   #13
Registered User

Join Date: May 2008
Location: daytona beach florida
Boat: csy 37
Posts: 2,844
Images: 1
Re: Alternator for a Perkins 4-108

I have a plain old Delco 12si that puts out 95 amps as tested at a shop. Any alternator rebuilder will sell you one for $120 including the wire to drive your tachometer. Cheap enough to get a spare. This on a perkins 4-108.
__________________
Take two at low eight
onestepcsy37 is offline   Reply With Quote
Old 21-05-2015, 18:41   #14
Guy
Registered User

Join Date: Feb 2013
Location: So. Oregon, USA
Boat: Seafarer36c
Posts: 4,308
Re: Alternator for a Perkins 4-108

Quote:
Originally Posted by Stu Jackson View Post
Guy, all engines, of course, are different, but here's how we do ours. Also scroll up to reply #33 about using the right bolts.

CRITICAL UPGRADES - DO THESE OR ELSE!!!
Yes engines are different but the engine in question was a Perkins. Our Perkins which looks perfectly stock, has no provisions for adjusting alignment. The mount the attaches to the engine is fixed in all directions. No adjustment is possible without welding up holes and redrilling them etc. etc. If the lower mount hole is badly worn or the lower alternator mount hole is elongated, you can loosen things up and try to reposition the alternator but then you are depending on a tight bolt to hold things in alignment, not an accurate hole. Maybe that is enough for a boat?
__________________
Guy is offline   Reply With Quote
Old 22-05-2015, 09:30   #15
Registered User

Join Date: Aug 2014
Location: St. Joseph, MI
Boat: 42' Heritage East Nova Sundeck
Posts: 53
Re: Alternator for a Perkins 4-108

Kind of expensive, but if you are going to be on the hook for a long period of time, this might be an option. I have heard some horror stories about bent cranks on the 4 cylinder engines with bigger alternators and too much tension.
Perkins 4.108 Serpentine Belt Conversion Kit | Foley Engines
This was just a quick google. I'm sure there are cheaper alternatives but I have 6.354 motors that I will do this upgrade on to prepare fort the loop in 4 years.
Good luck.
__________________

__________________
mcgann454 is offline   Reply With Quote
Reply

Tags
alternator, perkins

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
High Rated Alternator with Alternator to Battery Charger Rumbero Electrical: Batteries, Generators & Solar 113 18-07-2014 06:29
Alternator Mounting on Perkins 4-108 bobfnbw Electrical: Batteries, Generators & Solar 9 06-02-2014 09:08
mounting bracket for Balmer alternator on Perkins 4.108 asumpton Engines and Propulsion Systems 1 16-01-2013 23:16
Perkins 4-108 vs Westerbeke 4-108 world spectator Engines and Propulsion Systems 14 15-08-2010 18:33
Perkins 4-108 Alternator problem mmckee1952 Engines and Propulsion Systems 1 05-11-2008 13:45



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 16:35.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.