Re: converting 24v alternator to ribbed micro v (serpentine)

Barry Connor

Thank you Nick,
This is excellent information.
Early 2019 I had my engine serviced at Marina de Ragusa in Sicily, the technicians told me the pulleys were wrong. I didn’t want to try and replace the pulleys with no engineering knowledge.
You have just solved the problem for all early 54 owners. Thank you again.
Very Best

Barry and Penny
“SV Lady Penelope II”
Amel 54. #17
Sainte Anne anchorage Martinique 

On Sep 24, 2020, at 08:00, ngtnewington Newington via <ngtnewington@...> wrote:

Hi fellow Amel owners.

 I have never been happy with the Leece-Neville 24v 175A alternator set up on Amelia presumably as supplied by Amel. 

Namely a double V belt pulley of 230mm diameter driving a 85mm diameter pulley on the alternator. These pulleys were supplied for B section belts, i.e. 17mm across the top. There was endless belt dust and short belt life. I checked the specs on B section belts and the minimum pulley diameter should be 112mm although it is possible to buy a cogged belt that can run on a minimum 91mm diameter pulley, however in general 112mm diameter is the smallest for B section belts. So this 85mm diameter pulley was wrong for such big belts.

I found on eBay Leece-Neville part number K176101466, priced $30. This is a K section 8 groove pulley with 63mm diameter.  The bore is 7/8 inch with keyway to fit the alternator. The pulley was new and unused.

Micro v belts can go round much smaller pulleys. I think for the K section it is a minimum of 45mm. So no problem going round a 63mm pulley.

I then took the original 230mm double groove pulley, that bolts to the Volvo crankshaft to my local machine shop in the UK who milled it down to match the Leece-Neville one I bought. He did a superb job for £60. 

Please see the photos of the big pulley that has been machined down from 230mm to 200mm.

So I calculate that I now have a pulley ratio of 3.14 whilst before it was 2.7. Thus at idle (725 rpm on the engine) the alternator now runs at 2300 rpm and will be charging nicely. Where as before in idle it was running at 1957 rpm. The alternator only kicks in at 2000 rpm. So in the boat manoeuvring situation we will now have proper charge, and we all know how much power the Bowthruster uses.

The alternator is rated for a maximum RPM of 8000. The Volvo D3 has maximum rpm of about 2700 so I calculate that the maximum engine rpm will have to be 2547.

Seeing as that is really thrashing the engine and I never run it it that level apart from the once a year blast out. I will put a small sticker at the helm saying Max RPM 2500.

Total cost in US$ including new Gates Fleetrunner belt about $125.

Obviously when I get back to the boat I will have to align the alternator, but note how now both pulley are exactly the same width. It will be much easier than before where one pulley was 47mm and the other 52mm. The machine shop supplied me with a few spacers, washers of different thickness, to help but I may well have to have a washer made  for the final alignment.

Nick (in the UK)

S/Y Amelia AML 54-019 in Leros Gr


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