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Old 09-02-2020, 07:24   #1
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Small Marine Diesel Belt Alignment

My twin Volvo MD2020s are chewing thru belts at an impractical rate (like requiring adjustment every 3 hours of run time). I suspect belt alignment issues. I recenty resolved an automobile belt alignment issue by pressing the power steering pump pulley further on to the shaft...a common problem/solution in automotive environments. However, Ive never made such an adjustment on a small marine diesel. The means of doing so are not obvious, are there any?
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Old 09-02-2020, 07:41   #2
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Re: Small Marine Diesel Belt Alignment

Take a straight edge and find which pulley is most forward, hopefully it will be the crankshaft one, then by using washers under the pulleys that need to move forward shim them up.
The alternator you can of course often move in its mounts depending on how it’s mounted, the water pump isn’t usually moveable except by shimming.

Depending on your resources it may be that you can remove a pulley and have the backside of the mounting surface machined to remove material to move it backwards.

I had to put a couple of washers under my water pump and of course the alternator was easy to move.
I have a serpentine set up, and their alignment is likely even more critical than a V belt, the belt being flat.
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Old 09-02-2020, 07:48   #3
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Re: Small Marine Diesel Belt Alignment

What is different about your 2020 Volvos over a standard engine? are you using Volvo belts?

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Old 09-02-2020, 18:27   #4
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Re: Small Marine Diesel Belt Alignment

On my older Volvo (2003T) the alternator would shift out of position just enough to reduce belt tension. As most installations, it relied on clamping pressure on a long slotted arm. I finally put a jack screw on the arm leading to the adjustment on the alternator. Makes it really easy to adjust belt tension and secures the adjustment against future slippage.

Here is a (too expensive) model, I made mine up from miscellaneous parts.

https://www.westmarine.com/buy/balma...tors--15747918
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Old 09-02-2020, 20:17   #5
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Re: Small Marine Diesel Belt Alignment

Quote:
Originally Posted by Pete7 View Post
What is different about your 2020 Volvos over a standard engine? are you using Volvo belts?



Pete
Nothing unusual about MD2020s. Volvo branded parts are just a massive rip off...they do not manufacture a single part for their marine diesels...just spray them green and mark them up by 300%.

I use mostly Gates belts.
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Old 09-02-2020, 20:19   #6
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Re: Small Marine Diesel Belt Alignment

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Originally Posted by jamhass View Post
On my older Volvo (2003T) the alternator would shift out of position just enough to reduce belt tension. As most installations, it relied on clamping pressure on a long slotted arm. I finally put a jack screw on the arm leading to the adjustment on the alternator. Makes it really easy to adjust belt tension and secures the adjustment against future slippage.

Here is a (too expensive) model, I made mine up from miscellaneous parts.

https://www.westmarine.com/buy/balma...tors--15747918
Different issue, tension vs alignment. I do loath those damn clamping swing arms though...same thing on the MD2020s.
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Old 09-02-2020, 20:30   #7
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Re: Small Marine Diesel Belt Alignment

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Originally Posted by a64pilot View Post
Take a straight edge and find which pulley is most forward, hopefully it will be the crankshaft one, then by using washers under the pulleys that need to move forward shim them up.
The alternator you can of course often move in its mounts depending on how it’s mounted, the water pump isn’t usually moveable except by shimming.

Depending on your resources it may be that you can remove a pulley and have the backside of the mounting surface machined to remove material to move it backwards.

I had to put a couple of washers under my water pump and of course the alternator was easy to move.
I have a serpentine set up, and their alignment is likely even more critical than a V belt, the belt being flat.
I checked the alignment as best I could today. The PTO castings on the front of the main pulley make it inconvenient and less than accurate, but nothing dramatically off...one alternator maybe slightly angularly off, very slightly.

The inside grooves of the pulleys were a little rough with surface corrossion, gunk, and some old paint on the main pulley (what a d'ass idea to spray that Volvo green paint on the inside groove of a pulley!). Faired them as best I could w Dremel tool and sandpaper, then tensioned. Heading out w friends aboard tomorrow...will know soon if that helped.
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Old 09-02-2020, 21:08   #8
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Re: Small Marine Diesel Belt Alignment

Hi all,
The factory belt on my new Beta 30 lasted about 500 hours then broke.
Correct sized belts from auto stores stretched and powdered like there was no tomorrow.
I contacted Gates Aust; they suggested their XL 7395 as a heavier duty belt; they have been very good.

I think the single v-belt driving (in my case) a 65 amp alternator and coolant pump are just not up to the job in yachts where the batteries are often not fully charged; they just work too hard too long.

A year or so after I bought my engine Beta changed to a poly-vee wide flat belt as standard, but wanted $500 or so for pulleys to convert my engine.
I've stuck with the heavy duty Gates belt.

Rgds
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Old 09-02-2020, 21:23   #9
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Re: Small Marine Diesel Belt Alignment

It might be that the demands on the alternator outputs have increased leading to a longer charge cycle. How healthy are the house batteries? I also endorse the advice by “draughty” re Gates belts.
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Old 10-02-2020, 09:28   #10
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Re: Small Marine Diesel Belt Alignment

V belts come in a variety of different widths and profiles. Some autopart stores measure the length but ignore the width or profile.

On our westerbeke I eventually ordered the belt from a industrial supplier to get the correct one (3VX belt, 3/8 wide clogged)
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Old 10-02-2020, 09:43   #11
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Re: Small Marine Diesel Belt Alignment

If ( lack of ) pulley alignment proves to be an issue then another useful method of checking is to remove the belt(s) then place a straight tube or rod of suitable diameter and length into one set of pulley grooves and, holding the rod or tube firmly against one pulley, see how it "sits into" the other pulleys. This method automatically compensates for differing 'belt centre line to edge of pulley' dimensions and is very accurate.
Sometimes a long 3/8" ratchet set extension may be used very easily.

Many ordinary belts are running at close to or above their design capability in marine applications these days therefore the little extra money for high quality Gates or similar belts is usually very well worth it.

Best regards,

Niall.
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Old 10-02-2020, 10:13   #12
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Re: Small Marine Diesel Belt Alignment

There might be problem of differing profile standards between V-belt and pulleys (e.g. US vs. European standard). The problem is minor in case the V-belt profile differs from the groove profiles of the pulleys. The belt will simply adapt its profile once at the beginning within the first few hours of operation. However in case the involved pulleys present differing groove profiles, the belt needs to adapt to differing pulley profiles at each rotation, which provokes rapid deterioration of the V-belt. If this is the case, You need to uniform the groove profiles of the involved pulleys by replacing the pulley presenting the groove-profile different from the others.
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Old 10-02-2020, 10:27   #13
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Re: Small Marine Diesel Belt Alignment

Try Gates Green Stripe belts. Alignment is hard to check for sure. Also, watch out for proper belt size, thickness , angle etc.
I had one Yanmar I never could get right no matter what I did.
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Old 10-02-2020, 10:37   #14
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Wink Re: Small Marine Diesel Belt Alignment

Sulivar made a good comment and the issue could well be one of profile since not only are world metric and SAE profiles different but there are also 2 common SAE 'V' profile standards - A mainly for automotive and B mainly for industrial use.

If aftermarket alternators etc. are installed their pulleys are not always matched to the applicable engine specifications. That can create problems and the poor belt gets the blame!

Best regards,

Niall.

PS - Things such as this are far too complicated these days and the lack of true worldwide standards creates issues in many areas.
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Old 10-02-2020, 11:03   #15
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Re: Small Marine Diesel Belt Alignment

Quote:
Originally Posted by belizesailor View Post
My twin Volvo MD2020s are chewing thru belts at an impractical rate (like requiring adjustment every 3 hours of run time). I suspect belt alignment issues. I recenty resolved an automobile belt alignment issue by pressing the power steering pump pulley further on to the shaft...a common problem/solution in automotive environments. However, Ive never made such an adjustment on a small marine diesel. The means of doing so are not obvious, are there any?

A good straight edge preferably steel. It wouldn't hurt to check across the pulley faces at several parts of a rotation just in case you have a warped pulley;
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