Yanmar 2gm20F alternator prevents belt installation

[Brinky63]

I tried installing a Yanmar 2GM20F alternator belt on my engine but ran into an issue. The alternator has a small screw on the bottom that hits the oil filter preventing it from going down enough to place the belt on.

Belt code is YM-25132-003700, came in service kit MK-2GM20F from diesel parts direct, same code as a spare belt i have.

Alternator was service a while back after replacing the belt, suspect they might have added this to it somehow since i never had an issue before with the installation of the belt.

I purchased a car belt one size up but that fits just right in the meantime, will not be able to adjust it anymore.

Anyone else experience this issue before?

What does one recommend to replace the alternator which does not have this impediment?

 

[Tally Ho]

suspect they might have added this to it somehow since i never had an issue before with the installation of the belt.

It sure doesn’t look “new”, but there is a lot of belt dust all over, so hard to tell.

How much play in the alternator from fully tight to fully loose and resting on the oil filter?

Why not remove the oil filter? Maybe a good time to tackle that job too.

Greg

 

[dlochner]

As Greg notes, there is a lot of belt dust, could be an alignment or tension issue. Are you certain the oil filter is the correct filter? A shorter filter would would work.

The wires appear to be several ground wires, could they be relocated?

 

[Ralph Johnstone]

The alternator has a small screw on the bottom that hits the oil filter preventing it from going down enough to place the belt on.

Something not quite right there :

Am I correct in saying that your alt. is now located at the extreme portside of the curved adjustment arm ?

​

Looking at the underside of my alt, I see no protrusion as you have:

Please supply a wild guess as to how old your engine is. Also, please supply several pictures around the alternator at a slightly greater distance. I have trouble seeing how the alt. is mounted. A video around the alt. would be best.

Any guesses as to what that protrusion is on your alt ?

Please supply a photo of the ID plate on your engine :

 

[Brinky63]

Hi All,

Thanks for the feedback. Some info:

Boat is a Hunter 306 build of 2003, Yanmar 2GM20F build of 2003.

Lots of belt dust from the last belt, have not had time to clean up the engine. Wish my engine looked as nice as Ralphs!

Yes the alternator adjustment bolt is as far as it can go (to your white mark), which means that i cannot adjust it any further should it be required.

The oil filter is a Yanmar spec and comes with the maintenance kit. Removing it allows to place the original belt but then the alternator is in the way of installing the Oil Filter.

Not sure what the protrusion is, it's an electrical connection, might be the cable going to the panel in the cockpit . I’ll send some better photos and possibly a video for clarity.

Planning to remove the alternator all together to see if I can move it in another direction.

Any recommendations as to a replacement unit?

 

[Ralph Johnstone]

Thanks for all YOUR info @Brinky63 . Problems like this drive me vicariously nuts.

First off, you have exactly the same engine as mine (which is a 1997) as opposed to your approx. 2002 vintage. So what the hell gives ?

Planning to remove the alternator all together

An excellent move but handle it with kidd gloves as you remove it as you will "likely" be using it again for many years to come ............... UNLESS on the off chance the people who last serviced the alt. either added something (as you've suggested) or installed another alt. altogether.

Alternator was service a while back after replacing the belt,

Once you have the alt. out, could you please go over it with a fine tooth comb to see if you can find the ID sticker for the model number ? It should be :

HITACHI ALTERNATOR, LR155-20B 129772-7720, 12VOLT - 55AMP.

This was the original alt. which was installed in your Yanmar 2GM20F engine and worked well before "something" altered it. That small electrical piece you show looks to be so clean and tidy in its mounting set up, that it looks like an OEM component rather than an "add on" by someone at a later date. Crazy !

I've looked at few ads for this alt. and cannot see any protrusions like you have :

Alternator for Yanmar Marine 129772-77200, 12977277200, LR155-20B AHI0068

miltonautoelectric.ca

........................ unless something's changed over the last 20 years. Got to wonder if the body of the alt. can be rotated when it is re-assembled ? ? ? ?

Lots of pictures, closeups, videos, charcoal sketches, and whatever of the unusual device and the alt. casing please. I've never seen anyone complain about too many pictures being sent on a problem like this.

 

[Brinky63]

Hi All. I was able to move the small screw back more and out of the way which gives me the room to successfully install the Yanmar belt. The attached two photos show the alternator installed and also the position.

The connected cable goes into the harness, I've not had time to figure out what it does. Online photos from the API 20025 alternators (new) don't show this screw protruding either.

The screw is a really close to the oil filter, not sure if that can be a cause for concern down the line. I'm running the engine every other day to get some more stretch into the belt and hope to be able to move it a bit more from the filter.

Still wanting to buy a new one, the unit came with the boat when I bought her 13 years ago. Most info shows that a Yanmar 2GM20F comes with a 55 amp alternator, where this one is a 94 Amp. We just have the starter battery and house battery which are charged by solar, not sure if I need such a large Amp Alternator.

Any thoughts?

 

[mermike]

A longer belt would give you more clearance. I would move it away from the oil filter ASAP.

That alternator has been modified in some way. I wonder if it's a method to control the field voltage. Do you have any knobs or switches of unknown function aboard?

 

[Tally Ho]

I think @mermike is right…you need a longer belt.

https://forums.sailboatowners.com/attachments/alternator-vi-jpg.229360/

That photo show you have room on the adjuster to go with a longer belt and that would get the alternator up off the filter a little. Otherwise you might find yourself with an engine alarm going off and a bilge full of oil when the protrusion wears through or punctures the filter.

Greg

 

[Ralph Johnstone]

​

You are now playing a fool's game.

I can think of just too many ways for this to wear through your oil filter and for once in your life, the buzzer on your low oil pressure alarm just doesn't make as much noise as it should and your engine seizes.

I wish you'd looked a little closer at your alt. before sending us all on this wild goose chase. You simply have the wrong alt. for a 2GM20F. But no harm done so far.

If you ever do perforate your oil filter, major harm may be done.

 

[Maine Sail]

I tried installing a Yanmar 2GM20F alternator belt on my engine but ran into an issue. The alternator has a small screw on the bottom that hits the oil filter preventing it from going down enough to place the belt on.

Belt code is YM-25132-003700, came in service kit MK-2GM20F from diesel parts direct, same code as a spare belt i have.

Alternator was service a while back after replacing the belt, suspect they might have added this to it somehow since i never had an issue before with the installation of the belt.

I purchased a car belt one size up but that fits just right in the meantime, will not be able to adjust it anymore.

Anyone else experience this issue before?

What does one recommend to replace the alternator which does not have this impediment?
Thats not a stock Yanmar alt. Someone put a ground bond under one of the alt case screws. Just pull the case screw & move it..

 

[Brinky63]

Hi All, agree on the longer belt. also going to change the alternator. Thanks for the assistance.

 

[Brinky63]

View attachment 229370
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You are now playing a fool's game.

I can think of just too many ways for this to wear through your oil filter and for once in your life, the buzzer on your low oil pressure alarm just doesn't make as much noise as it should and your engine seizes.

I wish you'd looked a little closer at your alt. before sending us all on this wild goose chase. You simply have the wrong alt. for a 2GM20F. But no harm done so far.

If you ever do perforate your oil filter, major harm may be done.

Agree, I never thought it was something that we could move around.

 

[Brinky63]

A longer belt would give you more clearance. I would move it away from the oil filter ASAP.

That alternator has been modified in some way. I wonder if it's a method to control the field voltage. Do you have any knobs or switches of unknown function aboard?

none

 

[Ralph Johnstone]

Follow Maine Sail's post #11.

If he says it's a ground and hence easily moved, it couldn't come from a higher source, and you get to keep your larger alt. Keep it, it's most likely in A1 condition.

Weird things sometimes have an odd way of working out. This one did so go out and but a lottery ticket, it's bound to pat off.

 

[dlochner]

You will need to do more than just remove those wires and the ground stud. Those wires are part of some circuit, removing them will break the circuit, so they will need to be connected some where.

One of the wires looks to be heat damaged. The insulation is kind of bubbly and lumpy. That begs the question, how it get hot enough to damage the insulation? Tracing the circuits connected to this ground wires is important and replacing the damaged wire is as important. Once you have done this you can find a better place to ground those wires, perhaps to the DC- Bus.

 

[Benny17441]

Hi All. I was able to move the small screw back more and out of the way which gives me the room to successfully install the Yanmar belt. The attached two photos show the alternator installed and also the position.

The connected cable goes into the harness, I've not had time to figure out what it does. Online photos from the API 20025 alternators (new) don't show this screw protruding either.

The screw is a really close to the oil filter, not sure if that can be a cause for concern down the line. I'm running the engine every other day to get some more stretch into the belt and hope to be able to move it a bit more from the filter.

Still wanting to buy a new one, the unit came with the boat when I bought her 13 years ago. Most info shows that a Yanmar 2GM20F comes with a 55 amp alternator, where this one is a 94 Amp. We just have the starter battery and house battery which are charged by solar, not sure if I need such a large Amp Alternator.

Any thoughts?

The 94 amp alternator is not EOM equipment. A high output alternator is usually matched to a large capacity battery bank. They are usually fitted with corresponding wider belts and pulleys as they face stronger loads. That may explain all the belt dust and frequent replacements. The added loads also chew away at engine horsepower ( 1 HP per each 25A) and fuel consumption. If you have solar and single starter and house banks a 55 Amp is recommended.