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Old 12-04-2007, 15:33   #1
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Perkins 4-108 belts

I have several friends with 4-108 engines in their boats, and all complain about short belt life. Some of them have done the "straightedge" technique to insure pulley alignment ... but none of them have found the belt life to be acceptable. OK forum members ... what's the secret?
Bob
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Old 12-04-2007, 16:07   #2
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The 4-108 belt setup isn't ideal to begin with. The belt turns both the water pump and the alternator and, if you've got a big alternator, that introduces considerable load.

Nevertheless, with proper alignment and tensioning and the choice of a QUALITY belt, you should be able to get reasonable life from the belt.

Mine turns a 110 Amp Balmar alternator, as well as the water pump. For some years I was going thru belts pretty fast. Turned out to be an alignment problem and an alternator mounting problem: the bracket holding the alternator to the engine had a stripped bolt in the engine, and the damned thing wasn't tight.

After fixing these problems, I get several seasons on the belt with no problems.

Gates Green Stripe belts are good.

Bill
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Old 12-04-2007, 23:48   #3
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I agree. Belt quality is No.1 priority. Second is section size. Ensure you have the right section for the pulley.
If you are turning heavey loads like a big alternator, you should also fit a double belt system. For instance, btrayfors 110A alternator is ruffly a 2hp load. I have an 80A unit and I use twin belts.
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Old 13-04-2007, 03:52   #4
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I’ve always recommended high quality drive belts such as: Gates “Green Stripe”, or Dayco “HPX - Top Cog” belts.

See the excellent article:

Simple Techniques for Preventing Drive Belt Alignment Problems
by Dan Parsons
SIMPLE TECHNIQUES FOR PREVENTING DRIVE BELT

and

Proper Installation and Maintenance Can Prolong the Life of V-Belts
By John C. Robertson
Proper Installation and Maintenance Can Prolong the Life of V-Belts
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Old 13-04-2007, 09:12   #5
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Belt life has not been a problem since I alligned the pulleys and installed a better pulley on the crankshaft that does not "bottom out" the belt.

Also using "ribbed" belts from the NAPA auto stores.

Before I did the above, there was black dust flying around, now everything is perfect....

Turning a 150 amp alternator, and yeah, probably should have dual belts, but the present system works fine.
(The highest output I have seen from the alternator is 95 amps with the battery bank 50% down)
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Old 13-04-2007, 12:26   #6
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Hey Dag,
Where on Earth did you find a replacement crank pulley? Have heard from another 4-108 owner who blames "cheap stamped pulleys" on Water pump & alternator, as well.
By the by... anticipate being in Lake Sylvia around the 25th ... maybe you could stop by for a cold beer? Tell me all about cruising in Tajikastan
Bob
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Old 13-04-2007, 14:31   #7
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The cheap stamped pulleys can commonly be "A" section. Many Asian equipment are commonly coming out with "M" section now. You need a "B" section pulley and belt at minimum for these loads. An "A" section belt in a "B" section pulley would hit the bottom of the V and cause it to wear like you said CSY. Certainly a proper machind pulley is far supperior to the stamped one.
Wahoo, I have often had to take a machined pulley and mate it to the crank boss or even machine the Crank pulley if it is cast.
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Old 13-04-2007, 15:07   #8
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Quote:
Where on Earth did you find a replacement crank pulley?
Uh, wrong info, I must have been smoking crack..

The belt was indeed bottoming it out before, but I got wider belts, not a new crank pulley..Did not think before I typed.

I got a new pulley for the alternator, a machined one, also aligned better with spacers.

Quote:
By the by... anticipate being in Lake Sylvia around the 25th ... maybe you could stop by for a cold beer? Tell me all about cruising in Tajikastan
Well, I cruised in Kazakstan and Kyrgystan for a while.
Not much water there, but beatiful prostitutes..

Then went to Italy for a few days and broke my ankle there..

Not sure I can come down to Lake Sylvia and sip cold ones, but can try...
(Have not tried to drive my stick-shift truck yet...Nor climb into dinghies..Keep me posted however, it could work despite the cast and crutches)
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Old 13-04-2007, 18:09   #9
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Dag,
the plan is to stay at Lake Sylvia for as short of time as weather allows, and then head for West End ... planning to leave around 9:00PM. IF weather is gonna hold us ther for any length of time ... I'll try to dinghy over & see you ... PM me or E-mail me with your phone #.
Bob
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Old 01-02-2016, 09:08   #10
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Re: Perkins 4-108 belts

Have any of you tried upgrading to a serpentine belt ? There are a couple kits on the market that provide new pulleys and even a new water pump with the pulley already pressed on but these kits are pricey to say the least. Just wondered if any of you Perkins owners had tried this.
David s/v Sidewinder Oceanview Marina, Island of Samal, Philippines
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Old 01-02-2016, 18:44   #11
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Re: Perkins 4-108 belts

My 4108 runs a generator. Belt is 4 years old. Engine always runs at 1800 rpm. Maybe running a large alternator at low rpm is a problem.
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Old 02-02-2016, 07:01   #12
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Re: Perkins 4-108 belts

Thank you Lepke for the reply. I run my Perkins at 1800-2000 rpm when motoring (every 3-4 hours I bump it up to 3000 to clean it out ) and it's then that I have had the problems. I have realigned the three pulleys and that helped but I'm still concerned that the high output alternator is putting too much drag on the system for the one small belt to handle. IT worked just fine for years so maybe it's time to check the bearings on the alternator. I like the idea of the serpentine belt set up and was just wondering if anyone had done this and if so what was the most cost efficient way.
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Old 02-02-2016, 18:11   #13
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Re: Perkins 4-108 belts

I put high output alternators on my Detroit mains. I had to go to dual belts. Single belts can put more strain on the bearings if the belt is tightened too much because of slipping.

3000 seem kinda high for diesel and long life.
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Old 02-02-2016, 20:43   #14
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Re: Perkins 4-108 belts

Yes Lipke 3000 rpm is high but I only run it at that rpm for 5 minutes or so to heat it up and clean it out. This was recommended to me by a mechanic who helped me put on my head gasket while in Indonesia. This may seem sketchy to some but this guy was sharp and I feel blessed to have found him in such a remote place like Tabelo. Two belts is another option and a good one since it isolates the alternator but it means installing a tensioner and I have not found a easy way to do this.
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Old 04-02-2016, 17:02   #15
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Re: Perkins 4-108 belts

I upgraded to a serpentine belt from SW Diesel in So Cal. no slippage or wear after 3 years. 105 amp alt.
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