Many thanks for the information Dave M I am about to put the rubbing strips and the chine strips on. Still a fair bit to do but I suppose after this length of time there is no rush!. I have a few other models to sail,Cervia,Yarra tug Manchester Ship Canal Old Trafford paddle tug (all scratch built) and when the Mercury is finished I will start the 34" RAF fireboat, for which I have the drawing. When I learn how to I will forward some pictures.

HI peteinoz
Welcome to the site. I have a copy of Model Maker from Sept 1963 and the Maycraft Mercury 38" was advertised at A£6.12.6 another model was the Meteor 48" at A£18.18.9. Motors advertised in the advert included the Taycols from the Target to the Double Special, the Super 'Q' Orbits and Kako's and the Micromax Milliperm and Monoperms.
A quick search of the web produced http://www.vintagemodelworks.co.uk/?page_id=9 and I see the Mercury is similar to the Tarpon cabin cruiser. if this is the boat you have then a 550 would suffice, if you do not require fast speed a 555 would be more economic, both run off 12v. I have a fellow club member with a Tarpon and that runs all day on a small 24v motor (run on 12v SLA) from a vending machine.
It would be good to see a picture of your model and even better if you shared any build pictures.
Certainly of Vintage era and the model in the article looks superb. Just like the real thing and all lovely wood and varnish 😀
Hope this helps