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Loosening Alternator Belt

shank

.
Apr 20, 2016
83
Catalina 27 Lake Champlain
Hello,

I have an 82 Catalina 27 with a Universal 5411 and the drive belt (there's only one) keeps coming loose after a few hours of operation. I've really cranked down on the bolt circled in this photo but it still loosens up. I was thinking of trying a lock washer and maybe some of that non-permanent Loctite to keep it from shaking loose. Good idea?

As I was reading stuff about this issue, I came across the problem that the early versions of this motor have bad alternator mounting brackets and should be replaced right away. Can anyone tell if I have the bad version?

Thanks for any help
 

Attachments

NYSail

.
Jan 6, 2006
2,742
Beneteau 423 Mt. Sinai, NY
Do you tighten the other bolt as well? And yes a lock washers would help.

Greg
 

shank

.
Apr 20, 2016
83
Catalina 27 Lake Champlain
I haven't been able to tighten or loosen the little screw on the adjustment bracket at all. It's just frozen on there.
 
Sep 25, 2008
6,315
Alden 50 Sarasota, Florida
I haven't been able to tighten or loosen the little screw on the adjustment bracket at all. It's just frozen on there.
Don’t worry about the screw. It’s typically the bolt on the lower bracket attached at the block which loosens the most In my experience with that engine.

alternatively, if the alt is at its max travel, use a slightly smaller diameter belt
 

shank

.
Apr 20, 2016
83
Catalina 27 Lake Champlain
Don’t worry about the screw. It’s typically the bolt on the lower bracket attached at the block which loosens the most In my experience with that engine.

alternatively, if the alt is at its max travel, use a slightly smaller diameter belt
Ok, that's good to know. The small belt is also a good idea. I think I'll replace the whole bolt with a lock washer today because the edges on the head are starting to get worn off.

Do you know if I have the flawed alternator bracket? Old Bracket
 
Sep 25, 2008
6,315
Alden 50 Sarasota, Florida
Do you know if I have the flawed alternator bracket? Old Bracket
Not sure how a hunk of metal can be flawed. If it isn’t bent, cracked or rusted through, it’s not flawed.
I’d replace that screw with a proper bolt and lock washer. No doubt some prior owner (read - incompetent) broke the original one and replaced it with that quick fix.
 
Oct 22, 2014
16,115
CAL 35 Cruiser moored EVERETT WA
I would suggest reviewing the information on bolt issues and design issues with various alternators and their adjustments.

Here is a copy of a much longer article found here: Marine Alternator Installation - Tips & Tricks - Marine How To


Dual Foot / Saddle Mount Alternators Can be Quite Flexible
In this image we have a Westerbeke engine that used a teeny-tiny 1″ foot Mitsubishi alternator that really conformed to no “small-frame” standards other than its own. Westerbeke offers a bracket to convert to a Balmar or other 1″ or 2″ foot Delco/Motorola/Bosch frame type alternator but the pricing for this bracket is literally insane.

When a 1″ or 2″ foot alternator can’t work the 3.15″ Yanmar style dual-foot alternators can often be used in place of a 1″ or 2″ foot mount as seen below. This image shows a Balmar 6-Series dual-foot alternator mounted to the factory Westerbeke engine mount (red part). Alignment has been set and mocked up using shims and washers. Once the shim & spacer dimensions are known you can then hit a machine shop and have them make you the correct spacers in a one-piece design. In this case the multiple pieces behind the red engine mount and in front of the alternators rear foot, would be combined into one nicely machined spacer. You can always leave it as pictured too. I just prefer less shim-parts as opposed to more. I have noted what I refer to as the drift bushing in the rear foot more on this soon.



Here’s an example of what it looks like to have the spacer and shim pieces machined to minimize excess part count..










Dual-Foot Alternator Rear Foot Bushing
The Yanmar style 3.15″ dual-foot alternators (also called “saddle mount” or “Hitachi mount”) as well as the 4″ dual-foot J180 large frame alternators both use what I refer to as a rear foot “drift bushing“. It is really just a split bushing that is machine pressed into the rear foot but other than “drift bushing” it really has no identifiable name. It does however deserves some brief discussion.
This bushings sole purpose is to compress the front foot of the alternator between the pivot bolts head and the alternator mount. It also serves to “support” the aft end of the alternator. Under no circumstances should the drift bushing ever be removed and the two feet of the alternator “clamped” by the pivot bolt..
This owner of a brand new alternator did not know what this bushing was for, so he removed it.. Oh jeez…….


This is a saddle mount / dual foot drift bushing:

This image illustrates where the clamping pressure is applied with a “dual-foot” alternator. Only the front foot is under clamping force pressure. The rear foot is merely providing support. You can see pretty easily with this Yanmar alternator bracket why removing the drift bushing can result in breaking of the alternators mounting feet.


When installing a dual-foot alternator following the guidance below will result in a worry free installation:








Alternator Pivot-Bolts
An alternators pivot bolt would appear a rather mundane item to discuss but, using the wrong bolt can get quite expensive. In the image below the engine blocks aluminum alternator mount has been damaged by the use of the wrong size pivot-bolt. Using the wrong size bolt, one that is undersized, can allow the alternator to twist, under belt-load and can potentially cause damage.

If you let the above continue and ignore checking your belt tension and alternator when you check the oil. This damage destroyed the entire front timing gear cover of the engine.

Alternators are also susceptible to pivot bolt damage:






Adjuster Arm Issues & Solutions
Issue #1
An alternator adjuster arm is normally just a piece of plate steel that connects to the engine on one end and the alternator on the other end. Its sole purpose is to keep tension on the alternator belt. The steel arm is normally slotted, as can be seen below, and the bolt clamps the alternators adjustment ear to the adjusting arm. One problem with this is that the alternator ear is soft aluminum and the aluminum gets pretty hot. Through repeated expansion & contraction cycles, and on high vibration diesels, the bolt can often become loose as happened in the left side image below. In this case the bolt actually fell out completely.


Issue #2
The second issue I see, with fairly high regularity in regards to adjustment arms, is a relatively thin washer trying to apply pressure to the slotted arm. Due to the slotthere’s limited surface area to actually grab onto. What often winds up happening is the washer begins to “dish” or “cup”. Once it does this the original torque/tension is lost and the alternator ear looses its grip on the arm can slip and allow the belt to become loose. The grip on the adjusting arm below was lost when this washer “dished” under load.
Solution’s for Issues #1 & #2
In order to alleviate the issues associated with the images above I recommend using a bolt that will extend all the way through the alternator adjustment ear far enough to accept a washer, lock washer and a nut. A Nyloc or other locking nut is an added benefit here as nylon has a much higher melting point than your alternator should ever see. On top of the longer bolt the use of *an extra thick washer, such as the CMI Grip-It Washer will eliminate washer dishing & arm slippage.
*The Balmar AT-165 uses an extra thick washer on both sides because the adjuster ear has a vertical slot in it. For threaded ears an extra thick washer on the adjusting arm side is all that is usually necessary.







Setting Belt Tension
Just like belt alignment, belt tension is critical for optimal alternator performance. Too much tension is not going to necessarily be better than too having little tension. Both extremes are bad. Guessing at belt tension, using the Binford Mark I Thumb Press Tool, unless your really experienced with this, is not likely to result in a good outcome. New belts also need to be “run in” and then re-adjusted. In other words don’t just install a new belt adjust it and walk away. You’ll want to run the belt under load for a period of time then make a second adjustment.
The first step in setting belt tension is to identify the longest pulley span as show below.


Once you’ve identified the longest belt span you can click on over to the Gates web site and used their V-
Belt Tension Calculator. Simply input the type of belt you have, the belt width and whether the belt is new or used and it will give you a belt tension number to start from.
Now that you know what belt tension you need, use of the Gates KRIKIT tools can be used to measure the actual belt tension. A pencil styl tool can also be used but they are more difficult. The Gates KRIKIT tools are inexpensive and pretty easy to use.
Just place the tool in the middle of the longest span, align it in parallel with the belt and press until you hear/feel it “CLICK”. Now carefully remove the tool and read where the plastic arm is flush with the aluminum gauge. There are two Gates KRIKIT tools one goes to 160 pounds and the other to 320 pounds. The most useful for our applications is the KRIKIT II PN 91132 (bottom tool in image below).
 
Apr 11, 2010
859
Hunter 38 Whitehall MI
Hello,

I have an 82 Catalina 27 with a Universal 5411 and the drive belt (there's only one) keeps coming loose after a few hours of operation. I've really cranked down on the bolt circled in this photo but it still loosens up. I was thinking of trying a lock washer and maybe some of that non-permanent Loctite to keep it from shaking loose. Good idea?

As I was reading stuff about this issue, I came across the problem that the early versions of this motor have bad alternator mounting brackets and should be replaced right away. Can anyone tell if I have the bad version?

Thanks for any help
when I owned a Catalina 34 I was an avid reader / user of their Tech notes. If I recall correctly there was a very good write up by Stu Jackson on the alternator bracket and a design flaw that could lead to catastrophic failure of the bracket. The write up detailed how to determine if you had the problematic bracket, where to get the improved parts and how to do the replacement. As I recall it didn’t take me long to make the change. I’d suggest getting into the Catalina 34 Tech notes site or contact Stu (he’s an active participant on the forum) and ask him.
During my 34 ownership years (17) I relied heavily on his postings and on his advice. He really was my go to source.
 
Last edited:
  • Like
Likes: jssailem
Nov 6, 2006
9,225
Hunter 34 Mandeville Louisiana
The belt looks too narrow (or the pulley too wide). It should be sitting higher in the alternator pulley .. Scroll down to the page in the attachment that is titled "Wrong Belt" and look at how low the belt is sitting in the pulley.. The picture in the first post looks like that.
 
  • Helpful
Likes: jssailem
Oct 26, 2008
5,019
Catalina 320 Barnegat, NJ
That circled bolt looks like the pivot bolt to me. Even if it is loose, it shouldn't affect the belt tension. That screw with the phillips head looks pretty skimpy to me, but you say it is frozen and besides that, I don't see adjustment on that end anyway. It seems to me that your problem lies somewhere behind that hose in the picture at the other end of the bottom bracket. There has to be adjustment somewhere on that bracket that is loosening and causing loss of belt tension. I'd look for an adjustable end on that bottom bracket, and not seeing an adjustable slot at that scimpy screw, I'd guess it is at the other end where we can't see it in the picture. I'm not familiar with that engine or bracket BTW. :huh:
 
Jun 11, 2004
1,220
Oday 31 Redondo Beach
Don’t worry about the screw. It’s typically the bolt on the lower bracket attached at the block which loosens the most In my experience with that engine.

alternatively, if the alt is at its max travel, use a slightly smaller diameter belt
I agree. You haven't mentioned the lower adjustment bolt which is hidden behind the hose in your picture. That's the one that really holds the arm out there. Have you tightened that?

Also agree with Kloudie that the belt looks too narrow. Maybe this could be from excessive wear?
Either way, you should probably replace the belt while you are in there.

Also agree that you should swap out the screw at the end of your bracket to a more robust bolt. That existing screw looks a bit small.

I don't think you have the mounting system that needs to be upgraded but someone else might know better. I have an M18 that needed the upgrade and it did not look like the one on the 5411.
 
  • Like
Likes: Scott T-Bird
Oct 26, 2008
5,019
Catalina 320 Barnegat, NJ
@Richard19068 , I think you nailed on all 3 points:

1. The adjustment bolt is not in the picture. That is the bolt that needs to be secured when the belt is tensioned.
2. Swap out the belt.
3. Swap out that screw with the phillips head if it isn't the right bolt size.
 

shank

.
Apr 20, 2016
83
Catalina 27 Lake Champlain
Thank you for all of the replies. I've certainly learned a lot about belts and belt tensioning. The Gates site is really helpful. I replaced the belt in the spring and was never happy with it because it looked narrow and dried out like it had been sitting on a shelf for years so I'll replace that and look for the adjustment bolt again.

I want to say that I don't have one of the old alternator brackets (I hope) because there are a lot of scary stories about these things failing causing major damage. I found this on the C34 Tech Notes @quadrille38 suggested:

"Someone asked how you can tell if you have the old or the new improved bracket?​
The answer is simple and easy to spot - the old bracket that's prone to failure has the adjusting arm over the top of the alternator.​
The new bracket assembly has the adjusting arm under the alternator."​