Craig & Katherine Briggs
I hadn't though about the prop shaft alternator, as I removed mine some time ago (have a genset), but it certainly seems reasonable that the heavier SAE90 oil will present more resistance and likely slow the shaft alternator.
I'd say stick with the 10w40.
(PS. I think Bill Rouse's comment was that the C drive oil viscosity wouldn't materially affect the engine speed, with which I agree - but your comment was about the SN shaft alternator, with which Bill isn't familiar.)
---In amelyachtowners@..., <parkianj@...> wrote :
I am waiting in anticipation. Amel Martinique’s replaced mine 2 years ago (but we missed last season’s cruising). However I already had the parts which included a phosphor bronze copy of the wearing out bushing. An engineer friend of my son had looked at the schematic drawings of the whole set up and suggested£ that it would work better with a harder material. The seals were put in the way you stated with two facing the water.
In the meantime I’m keeping an eye on the colour of the oil........
Still don’t know whether changing to SAE 90 would slow down the prop shaft alternator. Anyone got a professional view?
Ocean Hobo SN96 Isles des Saintes