Beta 14 Alternator belt

[DavidGrieves]

Hi
I've been helping a friend out with his boat. It has a Beta 14 engine, it had been laid up for a while and it took quite a bit of attention to get it going again. There was a new alternator belt onboard (Gates 6216MC 10AV0900) . I fitted it, but after 2 hrs and when I checked the tension it was slack. I re-adjusted it and its at the end of its adjustment on the slot. I checked it again today and its slack again. I don't think its done 3 hours at 1000 to 1200 RMP.
Does any body know if the 900mm x 10mm belt is the right size?

 

[Concerto]

I cannot advise directly as it does depend on exactly when the engine was manufactured. This web page will be able to start a direct comparison and let him buy the correct one.
Which ‘V’ Belt do I need for my Beta 10, 14, 16, 20, 25? | Boat Parts and Spares

Edit: You could also buy one direct from Beta, it will only be slightly more expensive than the link above.

 

[pioneer]

I cannot advise directly as it does depend on exactly when the engine was manufactured. This web page will be able to start a direct comparison and let him buy the correct one.
Which ‘V’ Belt do I need for my Beta 10, 14, 16, 20, 25? | Boat Parts and Spares

Edit: You could also buy one direct from Beta, it will only be slightly more expensive than the link above.

Quite probably worth going to Beta. If you quote the engine number they will be able to advise on the replacement for the originally fitted belt. If the engine has been modified without keeping Beta in the loop then that's another thing altogether.