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Old 17-08-2015, 18:23   #1
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How to replace my yanmar 30 raw water belt

My raw water belt shredded. Do i need to remove the crankshaft to get my new belt on? New to sailing and not much of a mechanic. Please advise.
Thanks
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Old 17-08-2015, 19:11   #2
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Re: How to replace my yanmar 30 raw water belt

Yes, by all means remove the crankshaft, a good time replace the pistons too, maybe a valve job?


Sorry could not resist, no. Changing a belt should be very easily done with a minimum of fuss, of course it's a boat so......
Take some good pictures and post them. Someone will recognize your setup and give you step by step instructions


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Old 17-08-2015, 21:57   #3
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Re: How to replace my yanmar 30 raw water belt

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Originally Posted by Rdsykora View Post
My raw water belt shredded. Do i need to remove the crankshaft to get my new belt on?
No, you don't need to remove the crankshaft sheave.

Loosen the mounting bolts on the alternator and take its belt right off.

Loosen the mounting bolts on the water pump">raw water pump. You can then get the old belt off and just barely pop its new belt on. Then lever the water pump sideways so its belt is tight and tighten its mounting bolts.

Replace the alternator belt, lever the alternator so its belt is tight and tighten its mounting bolts.

======

You're going to have to tighten and change those belts regularly. The stock Yanmar Mitsuboshi belts are soft sided belts, to transmit more power. The contact angle on the alternator is small and they must transmit a lot of power, so they slip and wear. That's OK, that's how it is, check them regularly. You'll see.
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Old 18-08-2015, 06:49   #4
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Re: How to replace my yanmar 30 raw water belt

Changing a belt is a basic & routine maintenance procedure. Maybe you can recruit a more mechanically inclined friend to walk you through the process?

What type of engine do you have?

On almost all makes/models it is just a matter of loosening the bolts that hold alternator in position and swinging it toward the engine so it applies (or would apply) the least amount of tension to the belt. The belt typically passes over three pulleys, but may vary by motor: alternator, fresh water pump, main pulley (on crank shaft). Some raw water pumps are belt driven, some are not. With the alternator loose: put the new belt over two of the three and then walk it onto the third as you rotate the engine manually.

Its a good saftey practice to shut off the start battery switch before working on an engine...you wouldn't want an acciddental start to happen with your hands on belt & pulleys.

I bet there is a You Tube video out there that shows this process.
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Old 18-08-2015, 09:35   #5
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Re: How to replace my yanmar 30 raw water belt

If it is a 3ym30, then I have just done this on both mine. You don't need to loosen the alternator as the water pump is on a separate carrier. This has two bolts which you loosen and then the carrier can be moved to loosen the belt. It can then be removed and replaced.
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Old 18-08-2015, 09:54   #6
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Re: How to replace my yanmar 30 raw water belt

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Originally Posted by Rdsykora View Post
My raw water belt shredded. Do i need to remove the crankshaft to get my new belt on? New to sailing and not much of a mechanic. Please advise.
Thanks
I think it's the same as my 2GM 20. As the pump belt is behind the alternator belt, you need to loosen off the alternators 3 adjusting bolts until it's belt is loose enough to remove. Then loosen off the water pump belt adjustment.
Remove the belt and replace and adjust them both. I've never had a belt shred. I think you should somehow find out what caused that to happen.


Are the pulleys in alignment? Hard to imagine they are not. Was the belt too tight or loose or was something rubbing on it?? Or possibly an inferior or incorrect belt. Belts can have different V angles even though they might be the same length. They are type A or B or some such identification. The V angle should match the V angle inside the pulley which is why you could initially get a genuine replacement Yanmar belt. Or if you know the type and length (I have forgotten) any good belt shop will do. Or take along the pump you can easily remove along with the old belt for length. I hope all that helps.
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Old 18-08-2015, 11:14   #7
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Re: How to replace my yanmar 30 raw water belt

Hi
Its relatively easy, my only advice is be careful not to overtighten the belt otherwise you ruin the bearing. In which case you will need to replace the pump.
It might be a good time to replace the impeller.
Yanmar belts are relatively expensive and are odd sizes so I suggest getting a spare at the same time. Not necessarily that easy to find especially cheap alternatives.

Good luck.
Berty
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Old 18-08-2015, 14:42   #8
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Re: How to replace my yanmar 30 raw water belt

Oh I forgot to say if you remove the pump make sure the water intake is closed!
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