Alternator Belts and Cables


1. All high performance alternators require an upgraded output charge cable if replacing an existing lower output alternator. At a minimum, use 2GA for 120 to l40 amp units - use l/0GA for 140 to 220 amp units. We recommend 2/0 cable as the minimum output charge cable when using our ZCCJE1222 alternator. Personally, we use 4/0 cable to reduce resistance and gain additional useable output. The charge cable is the large cable connected to the output stud on the alternator & the other end attached to the POS post on the battery or bus bar. The large wire size ensures a minimum of voltage drop or attenuation, especially considering the cable will be running through engine spaces.

2. Check for worn out or undersized batteries. Load test batteries to determine condition. Bad batteries wreak havoc on a charging system. Poor batteries shorten an alternator's life.

3. Replace frayed wires & undersized battery cables. Remove alt clamp on battery cable repair ends. Replace with Heavy Duty, high quality parts. Upgraded cables will give the electrical system a giant boost in performance & reliability.

The importance of installing PREMIUM quality belts can not be over emphasized. Loose, Worn Out, or Glazed belts will not handle a high performance charging system. We recommend GATES Green stripe "MOULDED NOTCH" OR GOODYEAR HI-MILLER belts for replacement of V type belts.

Install NEW belts, adjust tension (Check with Manufacturer for specifications - Typical alternator apx. 100#s, See right (top row) photos, and run the engine for at least 15 minutes. Then re-tighten (adjust tension) to take up the initial belt stretch. Do not put off this critical step! Check belt tension often - Physically recheck (requires engine to be stopped) every hour for the first 5-10 hours of use. After that, check the belts visually every hour and physically check if the visual inspection warrants. When you are at a dock or achored for the evening, press to check (at a minimum) the depression (very rough guide 1/8" - 1/4") after engine shut-down. Slipping belts generate excessive heat at the pulley. Heat is then transferred to the bearing and breaks down the lubricant, causing early bearing failure. When belts become glazed replace them immediately. The alternator output voltage will decrease when belts slip. Slipping belts are the #1 cause of low voltage charging conditions. The images to the right (bottom row) show properly fitting serpentine and v belts on their respective pulleys. If your belt bottoms out, pulley is glossy on the bottom, or worn on the sides, you probably need to replace your belt, pulley or both depending on exact conditions. Consult an expert for guidance.
Tension Gauge     Tension Gauge

V-Belt properly fitting pulley     Serpentine Belt properly fitting pulley

6.Do Not Do - ILL Advised: Not to mention the Cost vs. Gain
A common question we receive is regarding how to modify the water pump pulley to allow for dual belts. Simply, the answer is NO. The water pump/pulley is not designed for the side loading that will be impacted by a device that requires two belts. A developing situation that then arises is that they then want to have a double sheave crankshaft pulley with split loading. First, they want to place one belt around the first sheave, water pump/pulley, and then on to the pulley of the device requiring 2 belts. Next, they then want to place the second belt around the crankshaft second sheave and then on to the device that requires the second sheave without going around the water pump/pulley. Simply, the answer is NO, again. You can not have belts of two different sizes to drive a device. Belt tensioning will never be equal on the two belts. All the devices will have uneven stress, belt wear, ... The two situations discussed above are to be avoided. We have received numerous emails from various sources that describe this scenario over and over. Normally, it is the result of someone attempting to be cute, lack of space, lack of $, .... Ultimately, a lack of understanding engineering principles will eventually cause failure regardless of personal requirements or resources. Do it right the first time or don't do it at all. One does not always get the chance to pull over to nearest dock (and fix it).

7.BELT and Pulley Size vs. Amp Loading (at 12vdc)
One of the most common questions asked. What is the smallest or largest belt / pulley combination may I install on my engine, water pump, alternator, .... The combinations of this question with different variables is endless. On your existing engine system, whatever the manufacturer designed it to have is what you have to live with without modification (Westerbeke is the only exception we have found to this rule, but not really because they were designed for higher loads even though the standard installation is a single 3/8" v-belt.). To increase your basic installed belts and pulleys beyond what they were designed for - Did you read 7?

Bottom line is as follows:
•   single 3/8" vbelt supports up to apx. 70 amps
•   single 1/2" vbelt supports up to apx. 94 amps
•   double 3/8" vbelts supports up to apx. 140 amps
•   double 1/2" vbelts supports up to apx. 300 amps
•   single 8 groove serpentine belt supports up to apx. 300 amps

Exception to carefully note: If your use a single 3/8" belt exceeding 70 amps up to a 94 amp load, be aware it will work, but possible ramifications are increased side loading of the water pump, alternator, and v-belt. This will probably decrease water pump and belt lifespans significantly. Extra spares are a must - Do not forget a spare water pump, not just the impeller. The corresponding limit for a single 1/2" v-belt is 120 amps.

8.Most often asked Question and Answer putting the above (4,5,6,and 7) in perspective
I have a model _______ (fill in the blank) Engine and I am tired of loose alternator belts and black belt dust all over the place. Do you have a pulley and belt kit to upgrade standard equipment alternator belt to serpentine? If so, how much does it cost? Does it replace the old pulley or mount to the old pulley?

Usually this situation comes about from one of three scenarios - Improper installation (alternator & pulley alignments), improper or lack of tensioning, or constant overload. Refer to 4 and 5 above regarding belts and tensioning. Regarding item 6 - Based on your engine size, you may be in a situation that you are overtaxing your existing alternator (battery bank size in excess of 500AH and using a single alternator of limited output). If your battery bank exceeds 500ah, certainly by 600-700ah, you probably need our second High Output Alternator (ZCCJE1222, 220+ amps). Also, the cost to do the mods you were considering are as expensive as adding a second High Output Alternator in the first place. Again, the mod you were considering is a no go item. Contact us via a phone call for full details regarding your specific situation.

Bottom Line - A properly designed /engineered system works perfectly with either a CORRECT & PROPER V-Belt OR a Serpentine Drive belt. Wanting to change to a serpentine belt system before the underlying problem is discovered and a proper solution path is chosen, is like prescribing aspirin for an unknown infection. It may possibly help in the short term, but the long term results will not be known and may cause destruction.

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