V-belt Tension

[1911tex]

There are details on the following method elsewhere on this forum if you search belt tension; maybe 9 months ago or so. Its a very easy and very accurate way using only your thumb and first finger. Grab the center at the longest distance between pulleys and twist either direction...should never be able to twist the belt more than 90 degrees. Tighten or loosen to hit the mark. No crowbars, boards, tools, etc.. Surprising how many automotive mechanics use this simple method which takes a second or two or spur of the moment. There are many videos by mechanics on YouTube describing this very common method.
Here are only a couple:

If you can put up with this dude...good advice:

 

[vanilladuck]

@1911tex, this one?

Early this morning as I was installing new alternator belt...

Neighbor boat had an old time boat mechanic working on his engine. This fella saw me sweating in the high temps/humidity and advised to drink lots of water. He asked how I was tensioning the new belt. I demonstrated the 1/2" deflection on longest length of belt. Started engine and the belt...

ericsonyachts.org

I found it earlier today when I was searching around

 

[1911tex]

BINGO! How well I remember...and still follow and recommend his tutelage !
Thank you!

 

[vanilladuck]

I used this technique today as well -- and told my friend about it. Sharing is caring!

 

[Prairie Schooner]

The alternator belt is too loose, but I've maxed out the adjustment to tighten it. It works, but there's too much flop for my liking. During the cooling system rebuild I put in an ABYC compliant hose which is thicker than what was there. *yellow outline* Now I can't move the arm up/in enough to get a smaller belt on. I purchased a wedge tool designed for installing tight belts, but it doesn't fit the pulley.

At this point, I'm thinking about fabricating a new alternator adjustment arm with a longer slot. *magenta outline* Though I haven't confirmed there is even enough room to push the alternator out further. I think there is room to put in a little bump to relieve contact with the hose. That would allow me to move the alternator in closer to put on the smaller belt.

Is there a simpler way to solve this than building new boat parts?

 

[Kenneth K]

If you think the wedge tool might help you get a smaller belt to fit, perhaps grind down the wedge tool first (or, cut a new slot in it) and see if you can get it to work?

 

[Prairie Schooner]

If you think the wedge tool might help you get a smaller belt to fit, perhaps grind down the wedge tool first (or, cut a new slot in it) and see if you can get it to work?

I was gonna return it, but it was only nine bucks. I'll give that a try. Thanks, Ken.

 

[Kenneth K]

Or, unbolt the pulley from the water pump, slip the belt on first and put the pulley back on.

 

[bigd14]

I have the same problem. I can just barely get the belt tight enough as is so I live with it. But when I first noticed the problem I went to an old school alternator shop and they had a huge box of old alternator arms that they let me pick through and take a couple that might work. Ultimately they didn’t work but if the wedge doesn’t work you might be able to find something at your local place that could be modified better than the existing arm.

 

[vanilladuck]

I can't quite tell, is that a Universal M25? Would the upgraded alternator bracket help with this?

 

[Prairie Schooner]

I can't quite tell, is that a Universal M25? Would the upgraded alternator bracket help with this?

Yes, Bryan. (That's in my signature, but I never see anyone's signature when using my iPhone. Maybe the same for you.) It is an upgrade by the PO, tho I don't know if it's The upgrade.
All the upgrades seem to rub that hose. This would be a good candidate for a water jet cut part. I will probably do that in the future to the tune of the magenta section in my photo. For now, if I can just get one size smaller belt squeezed on, I'll rest a little easier.
I also need to put in the larger diameter metric bolt others have pointed out.

 

[vanilladuck]

Ah, forgive me (2X) - I missed your signature and that IS the upgraded alternator bracket. Whoever plumbed my M25, but a piece of straight solid tubing between the hoses to connect to the water pump. You can kind of see it here under the adjustment arm for the alternator (pardon my messy engine):

 

[Prairie Schooner]

Ah, forgive me (2X) - I missed your signature and that IS the upgraded alternator bracket. Whoever plumbed my M25, but a piece of straight solid tubing between the hoses to connect to the water pump. You can kind of see it here under the adjustment arm for the alternator (pardon my messy engine):

View attachment 53073

Maybe that's what I shoulda done. I got a 4-ply auto performance silicone elbow and a stainless barb connector. Seemed like a good idea at the time. A metal elbow might be just enough.
NP on the signature. They kind of become wallpaper, and don't even show up on cell phones, mine at least.

 

[windblown]

I use a 2x4 or a crowbar or whatever's handy and tension the belt so it seems right.

If it comes out wrong I loosen the bolt and do it again.

Belt should not flog around while running, or slip, or be bar taut, or cause belt dust.

The human eye is a good tool for this adjustment.

Does belt dust suggest it’s too tight?

 

[peaman]

NP on the signature. They kind of become wallpaper, and don't even show up on cell phones, mine at least.

On my iPhone, signatures appear when viewed in landscape (sideways) mode.

 

[Frank Langer]

Does belt dust suggest it’s too tight?

Belt dust can also suggest that the pulleys are out of alignment. Careful assessment with a straight edge can show this.
Frank

 

[Christian Williams]

[Posted simultaneously]

I think belt dust is probably from misalignment of pulleys, or from too loose or from slippage.

Big alternators can make for initial belt slippage, especially if batteries are low and demand is high. There are workarounds. I haven't had any issues with my 100 amp Balmar and original Ericson belt system. .

 

[windblown]

Belt dust can also suggest that the pulleys are out of alignment. Careful assessment with a straight edge can show this.
Frank

At this point, my adjustment arm almost touches my oil filter. I have room on the arm to push the alternator out a bit. can I try a slightly larger belt?

 

[Christian Williams]

fabricating a new alternator adjustment arm with a longer slot.

Jeff, since that arm will come off the bracket, you could just take it to a welding shop and have them extend the slot an inch or two by welding on a piece of steel. I have had success with such projects and found welders to enjoy such problem-solving small tasks.

a slightly larger [longer] belt?

Deborah, sure, why not. Who knows if the current belt is the proper size, anyhow?

 

[Prairie Schooner]

On my iPhone, signatures appear when viewed in landscape (sideways) mode.

It works! Thanks Steven!