Belt for Perkins 4-108

[seabreeze384]

I have a 4-108 built in about 1983. It appears to have a stock Delco 55-60 amp alternator; probably the original. I can not find a number stamped in the alternator case and any paper label is long gone. Owner's manual mentions 3 possible OEM supplied alternators but my alternator is none of these. Recently I had the coolant water pump replaced and the mechanic installed a new belt for the alternator/coolant pump/drive shaft. Lately I've noticed black "dust" on the pulleys and some wear on the belt. I'm wondering if the mechanic installed the wrong belt. The size (length or diameter) is right but I think the profile of the belt isn't right. The pulleys cross sections are deep V shape, more or less. The belt cross section is a moderately shallow U shape, more or less. The bottom of the belt cross section doesn't fit into the base of the V shaped pulley. The top of the belt cross section rides along the top of the V shaped pulley. So there is an air gap between the bottom of the belt profile and the bottom of the pulley profile. Sorry of the lengthy explanation. Does anyone know the part number and brand of the original belt supplied on the 4-108 with the original Delco alternator? If not, does anyone know how a properly fitted belt should fit into the cross section of the pulleys?

 

[stnick]

I removed My alternator took it to a alternator shop had it rebuilt, shrink wrapped it for a spare.. purchased a 85 amp and installed it my self.. very easy !
the black dust does sound like the wrong belt. I;ll look tomorrow in my log for the belt size Stay tuned Lee

 

[larryhume]

Rick, I'm going to take a chance and say the I use a #9000 Gates. I'm not near the boat right now so I can't check the number. But I would advise you to use a high quality belt such as a Gates.
It is possible that the belt alignment is slightly off. That would cause the black powder.
You could take the belt off and bring it to the store to match it for size.
Larry

 

[paragon]

Don't know length or profile specs for belt but look at notched v-belts for better performance. Commonly recommended in commercial and industrial drive applications - see http://www1.eere.energy.gov/manufacturing/tech_assistance/pdfs/replace_vbelts_motor_systemts5.pdf
Of course a synchronous or serpentine belt is even better and Transatlanitic Diesel sells a conversion kit for Perkins. See http://www.tadiesels.com/serpentine_4108.html
Good to use if you are going to drive a high Amp (>100 Amp) alternator.

 

[dave_a]

Rick - when I bought my M383 it had a replacement Delco on it. This fuzzy picture shows the alternator pulley. It has the wrong size pulley, you can clearly see the belt well above the top of the pulley. Notice the belt dust too. If yours looks like the pic its sized wrong.

Your local alternator shop can easily install a correct depth pulley. (Just don't tell them it's on a boat so they can double the price). If you take the ALT to the shop you may want to have them verify its a shielded marine ALT. Some insurance companies deny coverge if you don't have one and have a fire.

I put a Gates "Green Belt" on 5 years ago with the correct sized pulley and haven't even adjusted it yet. 50 hrs/yr.
Dave






alternator

 

[jose santin]

Your problem might not be a belt. If the water pump was replaced/rebuilt, the pressed on pulley on the pump was not placed in the right position. Thus your belt might be out of alignment due to the water pump pulley.

 

[rene_m]

I just learned that the Perkins 4.108 came with two belt sizes.. a 1/2 wide and one a bit wider than that. i have seen quite a few 1/2 alternator pullys on the ones with the larger belt. this will lead to premature belt failure and a lot of rubber dust.
Some have a 12mm or 7/16 with belt some have the 1/2 be sure of what that alternator has first.

 

[pacifica]

Just in case somebody wonders into this thread - on my Perkins 4.108 1984 M384 I have Gates 9400 XL High Capacity V-Belt - like this one from Amazon.