Yanmar 3gmf 20 water pump belt

Engines, Drive trains, Propellers, Steering, Ground Tackle and other mechanical system
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msheehan1
Posts: 15
Joined: Thu Dec 11, 2008 11:40 am

Yanmar 3gmf 20 water pump belt

Post by msheehan1 »

I tried searching but I cannot find it can anybody explain how to swap out the water pump belt mine goes every couple years and I'm tired of paying someone to do it. I have loosened the alternator housing and tension bolts still cannot get the alternator belt off to get to the other belt. Thanks for your help
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RadioZephyr
Posts: 259
Joined: Mon Jun 27, 2016 10:04 am
Location: Boston, MA

Re: Yanmar 3gmf 20 water pump belt

Post by RadioZephyr »

Have you tried sticking a large screwdriver underneath the belt and turning the pulley so that the screwdriver rotates around it, and lifts the belt off? That always worked for me. If that doesn't work, maybe just remove the alternator entirely.

Another thing that I wish someone had told me years ago: the belt for the water pump should NOT be kept tight like the v-belt. It is supposed to be nice and loose, with only enough tension so that it keeps the pump consistently turning and won't fall off. If you tension it like the v-belt, you are putting too much pressure on the spindle, and will prematurely burn up the seal where it goes through the pump body. Looks like yours is loose enough, but I figured I'd put it out there for others.
Josh
Sunset Spy
F38, Hull #152
Boston, MA

Pearce
Posts: 65
Joined: Sat Feb 22, 2020 10:28 am

Re: Yanmar 3gmf 20 water pump belt

Post by Pearce »

Maybe you already are aware but one other trick is to flip the decompression levers on the top of the engine. This will make it easier to turn. Then rotate the engine with a screwdriver under the belt to slide it off as Josh describes.

Just have to remember to flip them back before starting the engine after putting the belt back on.

Thanks to Josh for the water pump belt tension advice.
Pat
Schoodic - F36
Beverly MA

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