Re: Improved 24v alternator pulleys and turbo heat shield

Alain Durante

Bonjour Nick,


Thank you very much for the information and I will try to find a good solution.




Alain Durante

Meige / Amel 54-21


De : <> De la part de ngtnewington Newington via
Envoyé : lundi 21 juin 2021 08:27
À :
Objet : Re: [AmelYachtOwners] Improved 24v alternator pulleys and turbo heat shield


Hi Alain,


This is copied from my email to the forum back 2020.


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.


So now that I have it fitted I can report that it works well. The only thing is that small pulley required a small spacer about 5mm for the nut to clamp it to the fan.


I also report that the belt that I am using fits nicely Gates FleetRunner Micro V 8PK1255HD


Kind regards





AML 54-019





On 21 Jun 2021, at 09:02, Alain Durante <info@...> wrote:


Bonjour Nick,

I also want to improve the drive pulley on my 175 A alternator so do you have any technical information and parts number to help me to do the modification?


Alain Durante

Amel 54-021 / Meige

-----Message d'origine-----
De : <> De la part de ngtnewington Newington via
Envoyé : lundi 21 juin 2021 07:39
À :
Objet : [AmelYachtOwners] Improved 24v alternator pulleys and turbo heat shield

Whilst in lockdown I bought a nice new heat shield for the turbo.  See below, the original was messy and shed fibre glass.
More importantly I re-machined the drive pulley to micro v PK8 And bought an off the shelf Reece Neville pulley to match.
They are now fitted and aligned perfectly.
I can report, but only after a couple of hours use, that it runs well at much lower temperature. Previously the belts and pulleys ran 100 degrees C now 52!
Also due to improved ratio, at idle the alternator generates 43A v about 12A before.
I calculate that  max rpm should be limited to 2600 as that will max out the alternator rating of 8000 rpm.
The Volvo WOT is specked at 2750. I plan to make a label at the helm to say max rpm 2600.
Frankly the only time I open the throttle full tilt is to blast away any soot build up but at 2600 it all seams a bit much anyway.
So far no dust but it is early days.
S/Y Amelia
AML54-019 Patmos


Join to automatically receive all group messages.