Fan Belt/Impeller

May 28, 2015
275
Catalina 385 Long Branch, NJ
I've just crossed 5 years and 500 hours on my Yanmar 3JH5E. I'm pretty sure I'm dealing with the original belt and original impeller. I've not had any significant issues with engine performance but I have noted that when running WOT, the temperature does seem to be about 10-20 degrees hotter on the temperature gauge than it was originally.

I will be flushing and replacing the coolant this year (I think its been 3 seasons since I last did that).

I'm trying to determine whether this belt should be replaced. It looks almost brand new but I was just reading that some of the newer belts don't show the wear the way the older belts showed.

Any opinions?
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Jan 11, 2014
11,323
Sabre 362 113 Fair Haven, NY
What's a belt cost? What kind of trouble will you be in if it breaks?

You might want to check the inside fo the heat exchanger to see if there is any build up blocking the tubes and check the seawater pump, that impeller may need replacing.
 

dLj

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Mar 23, 2017
3,374
Belliure 41 Sailing back to the Chesapeake
Is there a stated time period to change this belt for your engine? From the photos I see an alternator on the belt and one other thing I don't recognize - looks like a water pump? I don't know.

It's not a timing belt so I doubt if it breaks you destroy your engine, although loosing power and ??? Coolant??? Might be a real drag depending upon when it happens. In my case, it nevers happens at a time at all convienient ... More like in the middle of a shipping channel with a huge container ship bearing down on me and no wind... YMMV....

dj
 
Jan 11, 2014
11,323
Sabre 362 113 Fair Haven, NY
Is there a stated time period to change this belt for your engine? From the photos I see an alternator on the belt and one other thing I don't recognize - looks like a water pump? I don't know.

It's not a timing belt so I doubt if it breaks you destroy your engine, although loosing power and ??? Coolant??? Might be a real drag depending upon when it happens. In my case, it nevers happens at a time at all convienient ... More like in the middle of a shipping channel with a huge container ship bearing down on me and no wind... YMMV....

dj
The internal freshwater pump is up and to the left of the alternator and is driven by the serpentine belt. The seawater pump is driven off of a PTO on the port side of the engine, it is just to the right of the idler wheel in the photo.
 
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Tom J

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Sep 30, 2008
2,301
Catalina 310 Quincy, MA
You are fortunate to have a serpentine belt, and it looks to be in very good condition. The v-belts, such as the one on my engine, wear fairly quickly, and require occasional replacement.
The impeller, however, on your raw water pump should have been replaced a couple of times by now. The rubber that the impeller is made of deteriorates with age, so it should be replaced periodically, regardless of how many hours are on the engine.
 
May 28, 2015
275
Catalina 385 Long Branch, NJ
The impeller is definitely getting replaced ... I should have never let it go this long and I think I got really lucky on that front. I just spoke to my local shop and they obliquely indicated it should have been 2-3 years on the belt although some will go 5-6 years. I think they were politely telling me "5 years is beyond end-of-life stupid" ... so the belt is going to get replaced .... then I will be carrying 2 spares for everything instead of 1 spare ... I think I'm going to get on the every two year schedule and start removing the impeller during the winter.

I routinely sail across Ambrose Channel as well as the Raritan Bay Channel and NWS Earle channel ... so the concept of a belt going at an inopportune time is not a welcome thought.

We'll see whether the heat exchange is an issue once I have all of the new stuff in but I kinda think the heat exchanger is okay.

K
 
Jan 11, 2014
11,323
Sabre 362 113 Fair Haven, NY
The impeller is definitely getting replaced ... I should have never let it go this long and I think I got really lucky on that front. I just spoke to my local shop and they obliquely indicated it should have been 2-3 years on the belt although some will go 5-6 years. I think they were politely telling me "5 years is beyond end-of-life stupid" ... so the belt is going to get replaced .... then I will be carrying 2 spares for everything instead of 1 spare ... I think I'm going to get on the every two year schedule and start removing the impeller during the winter.

I routinely sail across Ambrose Channel as well as the Raritan Bay Channel and NWS Earle channel ... so the concept of a belt going at an inopportune time is not a welcome thought.

We'll see whether the heat exchange is an issue once I have all of the new stuff in but I kinda think the heat exchanger is okay.

K
Keep the old belt and the old impeller as spares. Rotate them out at the next belt change. Saves of one belt just sitting in the boat forever.
 

higgs

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Aug 24, 2005
3,627
Nassau 34 Olcott, NY
Impellers are not that expensive. Have a new one as a spare. It is a good idea to check the impeller every year or so. Not that hard to do. If you are running hotter than normal it is quite possible a vane on your impeller has broken off. Not only does this reduce the amount of water that it will move, but the vane itself is probably impeding water flow to your heat exchanger.
 
Jan 11, 2014
11,323
Sabre 362 113 Fair Haven, NY
Not that hard to do.
Depends on the boat.

The last required empty the sail locker, removing some panels and diving deep into the locker and contorting yourself to see the pump. Or, reaching through an opening in the counter top, then reaching to the back of the motor to find the pump while trying to remove the cover back handed and blind.

The new boat is a little easier. However, Yanmar wisely put the pump cover facing aft about 1 impeller width in front of the starter. At least by removing 1 small panel and lying on the sole of the head, I can see and touch the pump. It is almost easier to remove the starter to get to the pump assembly.
 
May 28, 2015
275
Catalina 385 Long Branch, NJ
In my case, with the Yanmar 3JH5E I have absolutely no excuse.

The impeller pump cover faces forward completely unobstructed. The fan belt comes off with three bolts loosened. One of the three bolts is a tightening bolt on the top of the alternator.

This is arguably the most wisely engineered engine for maintenance that I have ever owned.

As for my impeller, all vanes were intact but it was past its end of life. I removed it three days ago and the vanes are still in their compressed position.

As for the fan belt, it too has taken on the shape of the pattern of its mount ...

Not sure these are going to be replaced annually but I will be removing them from the engine during the winter moving forward.
 

Tom J

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Sep 30, 2008
2,301
Catalina 310 Quincy, MA
We'll see whether the heat exchange is an issue once I have all of the new stuff in but I kinda think the heat exchanger is okay.
With 500 hours on the engine, the heat exchanger should be fine, unless a piece of impeller, etc., causes a blockage. Plan ahead to some day pull the HX and bring it to a radiator shop to get it flushed and pressure tested. Just another preventive maintenance task not to be overlooked.
 
May 28, 2015
275
Catalina 385 Long Branch, NJ
With 500 hours on the engine, the heat exchanger should be fine, unless a piece of impeller, etc., causes a blockage. Plan ahead to some day pull the HX and bring it to a radiator shop to get it flushed and pressure tested. Just another preventive maintenance task not to be overlooked.
The heat exchanger will likely be a task for a future year ... for the first time through on that one I'm going to want to have a Yanmar mechanic onboard with me walking me through the steps.
 
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higgs

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Aug 24, 2005
3,627
Nassau 34 Olcott, NY
If you have lost one of the vanes on the impeller and it is restricting flow, you will continue to run hot. My Yanmar is a 3QM and clearing the exchanger is not difficult. The entrance end of the exchanger is easily accessible and there is a strainer where the vane would end up.