Worn Belts on R21-EC with 3YM30 Engine

B

Blue Healer

Member
Joined
May 17, 2010
Messages
22
Fluid Motion Model
C-24 C SE
Hull Identification Number
USFMLT2116H8
Vessel Name
Blue Healer
My 3YM30 engine has only logged 100 hours but the front of the engine is covered in fine black rubber drive belt dust and the raw water pump belt in particular is frayed.

My learned friends; What's goin' on? ......and yes, the belts are kept at the recommended tension.
 
Check for nicks or damage to drive pulleys. Check to see if belt is rubbing on something, especially the hoses. Andrew put out a notice and a fix about the hoses on the front of that engine, quite some time ago.

Gene
 
I have the same problem with my 3YM20. If you read any of Nigel Calder's books on marine diesel repair and maintenance he speaks to this issue. Apparently the pulley on the crank shaft of the engine and the pulleys on the raw water pump and the alternator are of differing degrees of pitch. If I remember the crank pulleys are usually 35 degree pulleys and most accessory pulleys are 37 degree pulleys. This difference accounts for the unusual wear. The ultimate solution for this is to replace the accessory pulleys with pulleys that match the pitch of the crank pulley. I have not done this yet but I do occasionally tighten the belts as this situation does cause the belts to wear on the edges which then causes them to slip which then causes them to wear more and so on and so on. I also make sure I keep an eye on them and change them out at regular intervals and I always have spares on the boat.

Eric
 
I think the factory should weight in on this. Andrew, can you shed any light on this issue? If the pulleys are different, how do we get it fixed?
 
Rick,

This really is not a Ranger Tug factory issue. This is a marine diesel engine manufacturer issue. Referencing Nigel Calder again, the engine manufacturers, in this case Yanmar, usually manufacture only the engine. They then purchase the accessory components from other vendors. In my case my raw water pump is made by Johnson and my alternator is made by Hitachi. Yanamar and most of the other marine diesel manufacturers don't overly concern themselves with the inherent discrepancy between the pitch of their crank pulley and the pitch of the accessory pulleys that they purchase from outside vendors.

As I mentioned in my earlier post the ultimate solution is to replace the pulleys as required to create harmony among all of the components that run off of the crank. To me, maintaining the proper belt tension, changing the belts at regular intervals and occasionally cleaning up the dust generated by the belt wear is much easier than changing out the pulleys.

Eric
 
Eric,
I don't know about you, but my 3YM30 motor is still under warranty. My raw water pump appears to be added by Ranger. All the other accessories on the engine appear to be original with the engine, which Yanmar should be responsible for. I suggested the Ranger factory should chime in on this because this may be a warranty issue and/or something that needs to be addressed for future production. Ranger has a direct line to Yanmar and can get a better/faster response from Yanmar than we can. If we do need to get replacement pulleys, I figure Ranger is better able to tell us what kind and where we can obtain the parts. I have tried to find pulleys before for other applications, and let me tell you, it is not any fun.

I do not (yet) have any of the symptoms you and Blue Healer are experiencing. I just looked directly down on the belt/pulley for the raw water pump on my engine and it appears the pulley is not exactly aligned with the belt. The inboard side of the pulley (the side closest to the crankshaft) is tilted a bit aft. I need to inspect this further to see if there is any wear, etc.

The pulleys for my alternator and fresh water pump are under a safety shield which will have to be removed for inspection. I won't be able to get to that today because I have other things to do this afternoon and evening, like take the grand kids to the circus.
 
I've noticed "black dust" as well. I've seen it on many boats I've owned (or helped service) with a small diesel engine (usually sailboats, usually Yanmar). Over the years I've found that I can cure the dust build up with a damp rag. A belt inspection when putting the boat to bed catches most belt condition worries and gives you time to replace them before the next outing if need be.
I've noticed that new belts seem to throw more dust until they "seat" then they will need a slight re-adjustment to take up any slack. The dusting process slows after that until It becomes worn out, glazed and brittle (mine last at least a season).
The last water pump belt I changed wasn't due to it "wearing out" but due to it's advanced age causing it to become so stiff it wouldn't turn on the pulleys ...just sat and squeeled (audable wear indicator?)...it was on the boat for at least 2 seasons.
As usual..always carry a new spare for each belt. I wouldn't recommend using an old belt as a spare..they were shot when replaced and won't get better with age(they will petrify tho').
The water pump is installed by Yanmar, not Ranger.
 
I would start by checking the belt pulleys to confirm that they are not damaged. The water pump pulley is especially vulnerable being as low as it is on the engine. The next thing to check for would be the alignment of the pulleys. The engines do come completely assembled from Yanmar including the water pump.

Ranger Jeff
 
Jeff
Yo' the Man!
Traces of rust in the pulley's V groove and misalignment of the raw water pulley bracket.

Yanmar support were wonderful enough to send out a Product Support Engineer. More about the outstanding support by Ranger Tugs and their suppliers later.

We removed the belts and discovered traces of rust in the pulley grooves next to the belts, where they sit in the pulleys, while the engine is at rest. The engine always comes to rest at the bottom of the stroke. The rust was hard to see and was only revealed when the belts were removed. This was dutifully smoothed back with emery cloth.

The Raw water pump pulley was also slightly out of wack. The pump and bracket were removed and the bracket tweaked back into alignment. The bracket looks gnarley but was soft enough to tweak in a vice using a large adjustable spanner.

For those of us who still believed in Santa Clause: Alas Virginia, there really is no international standard way of measuring V belt lengths (anymore). I was abruptly shown by the counter staff at my local transmission supplier, V belts from three different manufacturers, all marked as the same length, but each being significantly different from the other. We even found, of the two standard belts, for my engine, supplied by Yanmar, the alternator belt was so tight we could not press it over the pulley but had to remove a pulley to get it over into the groove and then remount the pulley. The adjusting bolt was of course loosened off at the time. The new raw water belt was so long that there is only just enough tension with the adjusting bolt at its maximum travel (it wont be long before I have to replace it again but with a slightly shorter belt).


LEARNINGS:
1. Look for rust in the pulley V groves when belts are removed.
2. Take old belts to your transmission supplier to get the right length belts and ignore the marked belt lengths.
3. The support, in all matters, that I have received from Ranger Tugs and their suppliers has been outstanding and I will write more about this in a new thread.

Cheers and thanks also to forum members
Graham
 
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