Sabre 28 Yanmar 2gm20f

[jlcarreiro]

New boat owner here. Twice now this season I have had to tighten the impeller belt. It seems the belt has stretched, when I try to tighten it the pully is all the way over to the stop, it won't move any more.

Is this normal? And is this the correct belt
Yanmar OEM V Belt 104511-78780 2GM(20)(F) 3GM(30)(F)

TIA, I've learned so much here.

[Compass790]

That is not normal.
Is the water pump">raw water pump working ok?, i.e. no leaks or noises & turns alright. It could be stretching because of load on it or bad alignment. They should last years.

You can get belts by the numbers if yammers belt has numbers on it.. Any auto chain store should have a range of belts, no need to buy yammers gold plated ones. If you find a knowledgeable sales assistant ( ok mission very difficult) they may find you a replacement. Sorry don't know part no.

[djousset]

I have the same engine and that is the V pulley part number that I have.
(104511-78780)

[tkeithlu]

Compass790 speaks wisdom. In greater detail: There is a reason the belt is stretching. That needs to be determined. Alignment: Check for rubber dust around the belt, and sight down it to be sure that it is not bent to the side as it goes from one pulley to the next. Then bearings: remove the belt and wobble each pulley in your hand, turning them as well. There should not be any wobble or bumping, just smooth rotation. Pay particular attention to the alternator and anything else adjustable: a worn bolt or weak tension arm can destroy alignment. It's your most likely source of trouble.

An auto parts store can measure your belt's length if it does not have the manufacturer's numbers. New belts are classified by "A" and "B" cross sections, nominal length in inches, and an "X" if it goes around a small pulley and needs to be knobbed to make it more flexible. Don't even think of paying Yanmar for a standard industrial item.

[zstine]

The OP didn't say it was a new belt, just a new (used) boat. the belt could be several seasons old and then I wouldn't be surprised that it's at end of life. In addition to stretching, the sides of the belt wears and it moves lower in the V, so it is going around a smaller diameter in the pulleys. In the North East, where boats sit for the winter, I would get a surface rust on the pulleys which, if not cleaned smooth, would cause excessive wear on my belts. I generally have to replace them every other season (~200hours), but for $20 it is no big deal. Maybe he should put a new belt on and see how long a new one lasts... note that this experience is based on an alternator belt on my Nanni engine, not Yanmar impeller belt.


Its a $12 belt from yanmar, so just replace and worry less:
https://www.bayshoremarineengines.com/yanmarbelt.aspx

[Compass790]

Originally Posted by zstine

The OP didn't say it was a new belt, just a new (used) boat. the belt could be several seasons old and then I wouldn't be surprised that it's at end of life. In addition to stretching, the sides of the belt wears and it moves lower in the V, so it is going around a smaller diameter in the pulleys. In the North East, where boats sit for the winter, I would get a surface rust on the pulleys which, if not cleaned smooth, would cause excessive wear on my belts. I generally have to replace them every other season (~200hours), but for $20 it is no big deal. Maybe he should put a new belt on and see how long a new one lasts... note that this experience is based on an alternator belt on my Nanni engine, not Yanmar impeller belt.


Its a $12 belt from yanmar, so just replace and worry less:
https://www.bayshoremarineengines.com/yanmarbelt.aspx

I need to shift to USA, yammer belts a lot cheaper there! 2.5x that here.

Your nanni experience is not transferable to his yanmar because his belt only drives the raw water pump. Much lower loading than driving an alternator=much longer life . Eg our ysm8 one is at least 600hrs old & probably a lot more. However we dont suffer from a severe pulley rusting in a temperate climate

[zstine]

Originally Posted by Compass790

I need to shift to USA, yammer belts a lot cheaper there! 2.5x that here.

Your nanni experience is not transferable to his yanmar because his belt only drives the raw water pump. Much lower loading than driving an alternator=much longer life . Eg our ysm8 one is at least 600hrs old & probably a lot more. However we dont suffer from a severe pulley rusting in a temperate climate

Yes, much lower loading. But he will only get much lower wear if he does not run high pre-load tension. Perhaps the OP is over tensioning the belt leading to excess wear and stretching? It only needs a little more tension than what is needed not to slip.
So a question for the OP. Why have you tightened it? Was it slipping or did it feel loose or something else? If not slipping, maybe it should feel loose as not much tension is needed to drive the impeller.

[lockie]

Originally Posted by Compass790

I need to shift to USA, yammer belts a lot cheaper there! 2.5x that here.

Tsk tsk! Don't you understand that the incredible difficulty of printing "Yanmar" on the box costs more than making the part?

Generic stuff like belts, filters, impellers, bearings, lip seals etc etc can almost always be bought at a fraction of the Yanmar price. Just take the old part in with you.

Cheers, Graeme

[Compass790]

Originally Posted by lockie

Tsk tsk! Don't you understand that the incredible difficulty of printing "Yanmar" on the box costs more than making the part?

Generic stuff like belts, filters, impellers, bearings, lip seals etc etc can almost always be bought at a fraction of the Yanmar price. Just take the old part in with you.

Cheers, Graeme

Oh maate I'm onto the local yanmar mafia, can proudly say I've never bought a part off them & never will, well unless a rich owner demands genuine & wont wait for USA parts.

Hurt me enough buying genuine from the USA & hurt even more when I found an alternative later.

Hate to reward them & love to supply other old yanmar owners with aftermarket parts knowing I'm shafting the mafia.

[lockie]

Yep, goodonya. I've compiled a short list of generic bits for my 2GM over the years. I'll post it here when I find it.

[CAR54]

My Yanmar 2GM20F alternator belt won’t retain its belt tension. After troubleshooting it turned out, it was missing a lock washer on the bolt used to adjust the tension.

Yes, I know it’s a different belt but could be the same problem missing lock washers.

[lockie]

Might help someone.


Generic parts for Yanmar 2GM with Kanzaki KM2A Transmission

Filters:
Lube Oil Filter LF3462 Fleetguard
Fuel Filter FF5260 Fleetguard


KM2A Transmission:
Input bearing NSK 32005XJ OD ~ 49mm
Output bearing NACHI 07087Y OD ~ 53mm
Input seal NOK AC1314A ID 25mm OD 39mm
Output seal KOYO-OR Mh5A 30445 ID 35mm OD 55mm

CW Pump:
Bearings: NSK 6200ZZCM NS7S 605
Seal: NOK AEO279A
Impeller: Johnson 09-806B-1
Belt: Mitsubishi 10x445 M17.5

[TrentePieds]

If the adjuster bolt moves all the way to the end of the slot in the adjuster stay, it may be because the belt that came with the new-to-you boat was the WRONG one when you took over the boat!

Remove it, read the number that determines the length of the belt, buy a new belt coming down one size. If you do not see a number, take the belt to NAPA Auto Parts or similar retailer. The clerk will measure it with his magic gizmo he keeps for the purpose. Then get the next size down to what he measures. Be careful to get a belt with the same cross section!

There is something called a "star washer". Put a strar washer under the head of the bolt, then put the bolt through the lug on the alternator, then through the adjuster stay, put a flat washer on the bolt, then a star washer, and then the nut. Tighten the nut appropriately.

When the belt is on, you should, midway on the longest free length twixt pulleys, be able to twist the belt 1/4 turn between your fumb and index. Any less of a twist, and the belt is too tight, any more of a twist and it's too slack. You can get gauges to do the job, but this will do. Inspect your belt before each start-up and modify your tension as required. If any very, very fine black dust is accumulating in the vicinity of the belt it is an indication either that the belt is too slack and is slipping, or that one of the DRIVEN pulleys is generating more resistance to turning than it should and that the belt is slipping for that reason. Both these conditions will abrade the belt. Thence the dust. If the tension is right but a pulley hard to turn, then THAT is a problem that needs rectifying.

Bonne chance

TrentePieds