Saving Old Seagulls

Hi everybody, first post so pleae excuse me if not in the right place, etc.

I have a 1973 40+ which will be used as a "get me home" motor on a 13 foot Dory and as a "pottering about" motor on a small inflatable, presumably both uses will be mainly at full throttle.

So, should I keep it as a 10:1 ...