Upsizing a V belt on a FL 120

[slowbutsteady]

Hi All,

I am in the process of upgrading from a leece neville 90 amp alternator to a balmar series 621 single pulley 100 amp alternator. I currently have a 3/8 inch v belt driving the alternator and water pump on my engine.

My understanding is I should upgrade this to a 1/2 inch belt to accommodate the extra friction from the higher output balmar.

Can I simply use the thicker belt on the same crank pulley and water pump bell housing pulley or do those need to be changed as well?

If so I may do a serpentine conversion kit as that's better all around, but it would be more boat bucks I don't want to spend right away.

Thanks in advance!

 

[Comodave]

Putting a larger belt onto the small pulleys won’t get you more capacity. You should change the pulleys to ones for 1/2” belts. At that point I would opt for the serpentine belt.

 

[O C Diver]

While probably not a good idea, if the pulleys are even slightly out of alignment and the belt is riding exposed above the sides of the pulleys, plan on carrying replacement belts.

Ted

 

[slowbutsteady]

yeah, that makes sense - if the material rides high enough to not contact all of the surface area on the crank pulley I may only be getting higher durability on the thicker belt but not more horse power to the alternator.

This may be one of those situations where I'm talking myself into spending more boat bucks on the serp pulleys that I should actually have. The install looks really easy, just the kits are pricey

 

[slowbutsteady]

@O C Diver - totally agree with your comment on having spares. I have not one, but two pre threaded spares ready to go. Because the belt isnt going to fail at the dock!

That said, knowing how reliable serp belts are I may just bite the bullet and convert to that and carry a spare pre threaded serp. I've heard if you get the alignment right the serp belts are damn near indestructible.

Sigh, and so a 1k project turns in to a 1.5k project yet again.

Thanks for the quick reply as always, fellow TF members.

 

[RT Firefly]

Greetings,
Is it possible and potentially less expensive to use 2 belts (double up all pulleys) rather than a serpentine belt?

 

[Comodave]

Greetings,
Is it possible and potentially less expensive to use 2 belts (double up all pulleys) rather than a serpentine belt?

I would either do this or serpentine belt. Also if I remember correctly the 120 is a PITA to change the belt. Maybe have to unhook some of the cooling system. I think I read a post about someone getting burned badly by the scalding hot coolant…

 

[Martin J]

Sadly from what I recall anything above 90amp normally requires 2 x 1/2" belts. There used to be a provision on the FL 120 to bolt extra pulleys on the crank pulleys to add a 2nd alternator. Do you really need 90 amp? I have a blue seas Manual combiner on my port engine I switch on at night passage to run my service requirements. This keeps the engine battery and service topped up. My stbd engine runs my Naiad stabilzer pump.

 

[Cigatoo]

We run a Balmar 100 amp alternator on a single drive belt. Ours is the Lehman 135 but for this discussion basically the same setup, Not sure if it’s is 3/8 or 1/2 inch wide. I will check for you. No problems with slippage or wear. I would try your existing setup and monitor it. I was told that 100 amps is max for the single belt but perfectly acceptable.

 

[Comodave]

100 amp is supposed to be ok with a 1/2” belt. Don’t know about 3/8”.

 

[SteveK]

Must ask, why upgrade from 90 to 100 amp. Seems like a lot of expense if the 90 is still working.

 

[hobbystuff]

I upgraded to a serpentine belt 3 years ago when I went to a bigger alternator. Zero belt dusting, and the belts last quite a long time.

It wasn't exactly a plug and play installation:

• Pulley alignment is critical to get right, and in order to properly accomplish this I had some shims of various thicknesses waterjet cut.
• The pulley that fits over the harmonic damper would not fit, it was just a hair undersize relative to the harmonic damper OD. I gave the pulley and harmonic damper to a machinist to give things a once over for a nice fit.

It was absolutely worth the effort though.

 

[Tator]

Have been running 150amp alts on both of my Lehmans for over 3000 hrs over 16 years. I have a 5/8 pulley bolted onto my original pulley. I still use the original pulley to power the water pump and small alternator that charges my start battery and provides the tach signal. I don't go over 120 amps at my cruising rpm and still use the original belts. There is a bit of dust after that many hours, but not enough to warrant the cost of changing to a serpentine set up. I use use Gates green stripe belts.

Tator

 

[Marco Flamingo]

I have 1/2 inch with a 100 amp Balmer. No problems. I'm sure that the engine pulleys are stock Lehman (see picture). I doubt that my 80hp Lehman came with wider pulleys than the 120, so it's likely that a 1/2 inch belt can replace the 3/8. In fact yours may have had a 1/2 on in the past and somebody replaced with a 3/8.

Since my stock crank pulley is a double V, I looked into getting the same for the water pump and alternator. Balmer wanted a couple hundred for the double V (others had a workable solution for $100). Even though I found a double V pulley elsewhere for less, changing to a double belt would be time and money spent for nothing but added complexity.

One would think that a double belt would provide a backup in case one broke. Most reported that the broken belt managed to get caught in the remaining belt and either break it or stretch and unseat it, so usually the "belt broke the suspenders."

I did change the hose routing so that I can easily change the belt if required. (You can just see my spare belt hanging in the upper right corner of the picture. My stock adjustment arm is replaced with a turnbuckle and hanging with the belt is a wrench to put on a new belt or adjust tension. A loose or broken belt is a <2 minute problem once diagnosed.)

Most important for an upgraded alternator is probably the external regulator with temp sensors. I found that the prior owner had sprung for an external regulator but then kept the factory "plain vanilla" settings. The regulator can and should be set to minimize stress on the belt. If I constantly needed the full 100A and set the regulator for that, I might think about a beefed-up belt system. But with my regulator settings I don't even get belt dust anymore.

 

[sunchaser]

I'm curious, which pulley is of concern and will presumably "slip" with only a 1/2" belt? The drive, alternator or water pump? Many of us have only the alternator driven by a 1/2" belt and have no issues with a 100 - 120 amp alternator.

I'm in the camp of try a fresh 1/2"belt and assess issues, if any.

 

[O C Diver]

I'm curious, which pulley is of concern and will presumably "slip" with only a 1/2" belt? The drive, alternator or water pump? Many of us have only the alternator driven by a 1/2" belt and have no issues with a 100 - 120 amp alternator.

I'm in the camp of try a fresh 1/2"belt and assess issues, if any.

Probably the alternator pulley. In most applications, slippage is a function of belt contact with the pulley. While the crank pulley requires the most power transfer to the belt (turning the water pump and alternator), the alternator pulley has a very minimal amount of contact area. The water pump takes little effort to spin.

Ted

 

[Comodave]

One advantage of dual belts is that they don’t have to be as tight. So the side loading on the water pump, etc isn’t as high.

 

[rslifkin]

One advantage of dual belts is that they don’t have to be as tight. So the side loading on the water pump, etc isn’t as high.

Larger belts would bring the same advantage. The more contact area you have the less tension you'll need to transfer a given amount of power. That's one of the big benefits of multi-v serpentine belts. Lots of surface area.

 

[sunchaser]

Probably the alternator pulley. In most applications, slippage is a function of belt contact with the pulley. While the crank pulley requires the most power transfer to the belt (turning the water pump and alternator), the alternator pulley has a very minimal amount of contact area. The water pump takes little effort to spin. Ted

Good point Ted. Like many engines, ours has a gear driven water pump, allowing a good wrap/contact area around the alternator with the need for a water pump pulley gone. Idler pulleys do the same in many engine applications.

 

[marcs]

FWIW, I have dual 1/2" v-belts on my 120s and as it happens just a couple of days ago one broke but I didn't notice as the other one took the load. Noticed from the squealing of the belts slipping on the next start up when the 120amp alternator and depleted house bank were too much for the remaining belt, at least at that level of tension and wear.


Good reminder to inspect your belts, check the inside of them for cracks between the teeth. Mine were overdue for a change, one of the "teeth" actually got stuck in the pulley and came off.


An easy fix at anchor with a cold engine/ER and spares already wrapped around the cooling hose. Would be a very unpleasant and potentially dangerous fix at sea with hot coolant with a single without spare belts in place.

 

[DennisB1]

Check the alternator output verses alternator rpm. Determine the max rpm achievable with your engine and typical cruise rpm’s and determine the related alt rpm. You may never achieve the 100 amp output with extisting pully diameters. As suggested earlier you may already have pulleys designed for half inch belts. One belt drive should not bs a problem.

 

[catalinajack]

A single 1/2 inch belt is good for up to 100 amps. I have 100-amp Balmars on my Lehman 120s. At best, they put out 65 amps each in my system so the single 1/2 belt is more than sufficient. Just because an alternator is rated at 100 or 120 amps max output does not mean that they will.

As for rigging a spare belt such thatt it can be swapped without removing a coolant hose, I have no such need. See the pic. Got the idea for this setup on a thread on this forum. The turnbuckle makes adjusting the v-belt tension quite easy.

 

[Cigatoo]

The belt on our 135 is in fact 1/2 inch wide. 100 amp Balmar alternator My guess is your pulley will accommodate the 1/2 inch belt. If it doesn’t try the 3/8 and monitor it. I think you will be fine

 

[Mike GB32]

skowbutstead-
Would this be of any help to you?

https://www.trawlerforum.com/forums/s68/balmar-pulleys-fl-120-a-62199.html

 

[slowbutsteady]

Thanks all, lots of great info here. I figured I wasn't the only one who worked on a project like this.

A little more info that might help frame the situation:

The Balmar upgrade is in response to my 90 amp leece neville alternator actually failing on my last trip. I spent three days on the hook and was at about 55% SOC on my 600 AH AGM house bank. Then I did a 6 hour passage at cruising speed. On startup and first run it was generating 60 amps and it gradually worked it way down to 15-20 amps after the first two hours as the alternator got warmer. This has always been par for the course for me so I thought nothing of it.

Once it managed to get the batts up to around 75% SOC four hours in to my cruise I noticed my voltage readout fluctuating between 14.3 and 15.1 in an oscillation about every two seconds. You could also hear the engine load revving a bit in the same timing. As you could imagine, my tach started jumping around as did my other analog gauges with the voltage flux. Then after about an hour of that (I didn't have a good place to stop and diagnose so I pressed on to the nearest marina with shore power about an hour away) the tach died completely and the alternator stopped producing a charge at all. Voltage dropped to its resting 12.7 volts and I knew my alternator diodes had packed up and died for good (point of info: My AT is connected via a 150 amp ANL fuse directly to my house batteries. Checked that too and it was 100% fine. I also tried a spare at the dock just in case)

Its a relatively new alternator (5 years or so?), and I had already long wanted an alternator that would 1. charge at appropriate voltage profile for my house batteries and 2. have temp sensors for the batteries AND the alternator casing to throttle back the amp output and prevent any damage to the alternator. I think the Leece Neville was simply being asked to do too much. I also think at proper RPMs the Balmar will actually output a more consistent charge as it is designed for this application. Also - My old sailboat had a Balmar 6 series 60 amp alt on a teeny tiny 12 HP yanmar and I was very pleased with it - worked like a charm and was super reliable.

The serp belt upgrade was just out of my concern of belt wear AND putting excessive sideways pressure on the belt driven water pump. I know the serp belts don't have to be as tight and have much better traction. Then there is also that confounded hose that requires drainage of coolant (I haven't modded this yet - but I see some posters here have).

Anyways, my plan as of this moment is to install with my existing setup and put a 1/2" belt and pre threaded 1/2" spare on to test everything out with an eye on the serpentine kit upgrade in the near future. I don't have any more long trips at anchor planned this season (because of work - boo!) and will probably only be doing weekend trips close to home.

I will report back with my findings here for everyone's edification and information. Hope this helps another lehman owner out there too!

 

[Old Sea Dog]

CJ. Is that hose configuration readily available? From whom did you order? Have a Balmar on my "new to me" '79 GB 36.

Sent from my SM-G715U1 using Trawler Forum mobile app

 

[Marco Flamingo]

OSD,

Here are the details. The hack is for a 80 hp Lehman, so check the water pump connections for measurements. https://www.trawlerforum.com/forums/s6/my-lehman-coolant-hose-hack-60596.html

 

[Tim]

Alternator Belt

I am using a single 1/2 inch belt on a 1000 amp balmar alternator with no problem. Instructions on balmar regulator advise to start with belt saver setting at 0 and if dusting increase to 1 if still dusting go to 2 etc. with the smart regulator you can manage the strain on the belt so give it a try before changing anything. This on my 3208na cat.