V-belt Tension

[Kenneth K]

Just curious what others are doing to adjust v-belt tension. I have a Universal M-25, but this issue should be similar to many engines. M-25 service manual says to tension belt so it deflects.25-.35” deflection (7-9mm) @ 20lbs deflection force. I tried my best to do so (using a fisherman's scale) when I installed a new belt last year (a Gates XL 7390 belt, after completing the alternator bracket upgrade). Judging by the visual "slop" in the belt (belt oscillates about +/-1.0 belts heights up/down with engine running), I always felt tension was a little loose. Still, I never heard any squeaks or saw any signs of slippage.

Going back to the factory specs of .25-.35"deflection, I thought: "Well, that's for an old 1985 belt." Wouldn't a new, modern belt be likely to stretch less (meaning, too loose with the stated amount of deflection). But then, wouldn't a new, modern belt with better rubber compounds and grooves have more grip even with less tension (so maybe the .25-.35" at 20 lb is okay).

There are various tension meters available, but without a chart showing the recommended tension for a particular belt, the meters don't help much. Gates' website shows no tension charts for XL belts specifically. A second belt that came with the alternator bracket kit was a Gates 3VX400. Gates' website does show tension settings for 3VX belts. The biggest visual difference I see between the XL and the 3VX is that the former has different/alternating rib sizes, while the latter has uniform ribs.

 

[Christian Williams]

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.

 

[GrandpaSteve]

I bought this and it works great:

https://www.mscdirect.com/product/details/35438209

 

[Kevin A Wright]

I use my index finger to push in the middle of the belt with what I estimate to be about 20# of force and use the Mk 1 eyeball to see if it deflects 1/4 inch. If it is about right and no belt dust or signs of slippage I consider it good to go.

Kevin Wright
E35 Hydro Therapy

 

[tenders]

I go by eyeball too, and by ear. If it's tight enough to charge and doesn't squeal or slip, it's within parameters. It isn't rocket surgery, but, then again, I have pretty good access to my alternator in my installation.

Don Moyer has a little different take on the tensioner system for Atomic Fours:
https://moyermarine.com/product/alternator-tensioning-arm-ovel_04-1_546/

 

[footrope]

Belt dust

When belts are new, during the first few hours of use, you may get a little dust. On my engine this is normal. I clean it up and keep an eye on it. If all is well, it stops after a few hours.

For tension setting I use the manual (finger) test for proper deflection as described above. As long as the belt doesn't flap at any normal engine rpm, it will likely be just fine. I don't think I have ever reset the tension after the belt gets a few hours on it, either. I haven't looked at any manufacturers charts, but the distance between pulleys has a small effect on the acceptable deflection, but the no flapping admonition is always correct.

I don't think v-belt materials or characteristics have changed so much since 1985, so you should be fine using the guidance from Universal for your engine.

 

[Frank Langer]

I read recently that the belt should ride between the sides of the pulley and not touch the inside base. I don't know why that makes a difference if the tension is correct, but that's what they said. Belts do stretch a bit in the first few hours of use, so may need adjustment after a few hours use.
I'm guessing that buying the original part at a marine shop would be more expensive than at an auto supply, though I haven't checked that out.
I also understand there are different types of belts - - ribbed, etc. Does anyone have any recommendations on a preferred make and size for a 16 hp 5416 universal diesel?
Frank

 

[Captain C]

Christian when you say you use a “2x4 or crowbar” where do you apply the pressure?

I’m new to this job and trying to figure out how to tighten. I Assume u loosen the alternator arm to move the alternator out a bit. Do u “gently” hammer down on the arm? That seems wrong and probably is.

Also, I noticed when the engine is running there is some play from forward to back in the top pulley in the alternator 3 pulley system. Is this normal or should that be solid with no play?

i think the intermittent screeching of belt is from either the loose belt, loose pulley, or a combination of both.

Dave
1985 Ericson 32-3

 

[907Juice]

I think he means as a way to pry and not hit. Find something long and strong and squeeze it between the alternator and something on the engine block. Use leverage to push/pull the alternator out and tight. Then tighten the bolt. It is tight enough when you can push on the belt in a Perpendicular manor and it deflects an inch or so.

Christian when you say you use a “2x4 or crowbar” where do you apply the pressure?

I’m new to this job and trying to figure out how to tighten. I Assume u loosen the alternator arm to move the alternator out a bit. Do u “gently” hammer down on the arm? That seems wrong and probably is.

Also, I noticed when the engine is running there is some play from forward to back in the top pulley in the alternator 3 pulley system. Is this normal or should that be solid with no play?

i think the intermittent screeching of belt is from either the loose belt, loose pulley, or a combination of both.

Dave
1985 Ericson 32-3

 

[tenders]

On some of the alternators I’ve worked on, including the one on my Atomic Four, there is a small notch on the casing, opposite the side of the adjustable hold-down bolt, right next to the ventilating fins on the moving pulley.

It doesn’t look like it’s supposed to do anything, but that notch is there to accommodate a small crowbar, like a “Wonder Bar.” I think I’ve also substituted a large flat-bladed screwdriver.

To set the tension of the belt, you loosen the nut on the hold-down bolt, insert the blade of the crowbar into the notch, and with one hand you lever up the tension on the belt using the engine as the fulcrum for the crowbar, and with the other hand you tighten the nut on the hold-down bolt to maintain the belt tension.

It’s so simple to do this given the access to the alternator I have on my boat that I’ve never been interested in the jack-like belt adjustment gadgets.

If you have more convenient access from other directions, as 907Juice mentions you can do similar lever work using a 2x4 from underneath the alternator, etc. But that notch is really handy if you can use it.

 

[toddster]

I bought this and it works great:

https://www.mscdirect.com/product/details/35438209

I think I might need one of those... does it fit between the pulleys and you turn it to force them apart?
Now that I've had a few vehicles with tensioner screws designed in, it drives me nuts to work on something that cost thousands of dollars and doesn't have one. Just a couple of weeks ago, the belt on the scuba compressor seemed fine, per backyard mechanic standards, but tanks were taking 10 minutes extra to fill. To get it to actual (very tight) manual specifications, I had to use a weird combination of pipe clamps to pull the motor away from the frame. Most of the time, I can pry a motor with one hand and work the screws with the other, but this thing required four hands.

 

[Captain C]

I was able to figure out how to tension the belt...thank you.

The pulley circled in red still has some play to it. I can see it wobble on its axis ever so slightly. And when it does I can hear the screeching sound similar to a loose belt. It's not terrible, but also doesn't seem right either.

This is not normal, correct?

I have a feeling I'm going to have to get the yard involved in this one.

 

[toddster]

Umm... water pump bearings? Darn - there goes a few boat bucks that could have filled the cooler with frosty cold ones this summer...

 

[bgary]

View attachment 24841

The pulley circled in red still has some play to it. ...when it does I can hear the screeching sound similar to a loose belt.
I have a feeling I'm going to have to get the yard involved in this one.

Of all things to repair on a motor, that coolant-pump is one of the easiest. So simple even I could do it (and did, last summer)

http://www.ericsonyachts.org/infoex...-coolant-pump-source-and-ID&highlight=coolant

Bruce

 

[Captain C]

Thanks for the confidence boost Bruce. After lots of reading and googling today I'm going to attempt the job. My boat is a 1985 32-3, #627. I assume the parts are the same as yours, Universal 25M, Kubota D850. Will confirm tomorrow after a trip to the boat.

This is a new boat for me (first summer with it) and although I've sailed for 20 plus years, I've always had the yard fix every problem I encountered, no matter how big or how small. And I'm sick of it! I want to learn to fix things on my boat. I don't want to rely on someone else.

Hopefully this is not a misguided adventure that will cost me more in the long run...we'll see!

 

[GrandpaSteve]

Thanks for the confidence boost Bruce. After lots of reading and googling today I'm going to attempt the job. My boat is a 1985 32-3, #627. I assume the parts are the same as yours, Universal 25M, Kubota D850. Will confirm tomorrow after a trip to the boat.

This is a new boat for me (first summer with it) and although I've sailed for 20 plus years, I've always had the yard fix every problem I encountered, no matter how big or how small. And I'm sick of it! I want to learn to fix things on my boat. I don't want to rely on someone else.

Hopefully this is not a misguided adventure that will cost me more in the long run...we'll see!

You are doing the right thing. Explore how much you can do yourself and then, after you see tools or expertise is needed, buy the tools when they are less than the yard cost, but pay for the real experts when necessary. Often tools for a one time repair cost less that an hour of boat yard service.

 

[L-G Harvey]

5416 belt replacement

...Does anyone have any recommendations on a preferred make and size for a 16 hp 5416 universal diesel?
Frank

Not sure if this is still relevant, but I have very recently been looking for the same thing since I had some trouble with the alternator mounting bolt which came loose after the nut somehow vibrated off. Anyway, all that is replaced, tensioned and adjusted using manual and visual method, but I think the belt could be changed (or that at least I should have a spare). Found this replacement online for $21:
<style type="text/css">p { margin-bottom: 0.25cm; line-height: 120%; }a:link { }</style> http://discountmarinesource.com/sto...uct/product&path=11758_11764&product_id=34465

Seems like a fair price. Could not find any similar belt from auto replacement shops.

Cheers,

Louis

 

[Christian Williams]

Regarding the bolt that holds the alternator--the long one through the ears:

It should fit snugly. Often replacements were the wrong size--including those shipped with the M25 upgraded bracket. That causes all sorts of annoyances, and the cure is a slightly thicker bolt.

These alternator threads also hear from folks who can't budge the alternator. Both the long bolt and the arm bolt need to be loosened before tensioning the belt.

 

[L-G Harvey]

Alternator bolts...

Christian: that may be what happened, since the bolt that loosened was not snug at all. I did replace it with a slightly larger one that fit more snugly, and I used a proper locknut to secure it.

By the way, I 'm a fan of your videos!

Louis

 

[vanilladuck]

Had a friend on my E32-3 this weekend and he noticed my belt was a little loose (the reason we were looking in the engine bay is probably a story for another thread). Before we started adjusting he ran to his boat and grabbed the belt tensioner jack that @GrandpaSteve linked above. Talk about the right tool for the job. I ordered one immediately