This is a peach of an engine. We bought it with a boat a guy from littlehampton yacht club, who bought the engine off another member who said he got it from the RNLI.
It starts on the button and has some service history. Here’s some of the spec:
I also have it listed here: http://www.outboards4sale.co.uk/detail/fatherID/35/TypeID/50/ListingID/16/furl/mariner-40hp-ex-rnli-outboard-1000