It's probably Ron Warring's 'Project 66', in the Jan/Feb/Mar copies of the 1966 Meccano Magazine. If so, we are talking about a 22.5" balsa hull – slap in my 'EeZeBilt' range. The magazines, with plans, are available for free on the net here:
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I have found that a small cheap brushless – typically an EMax CF2822 (get one off ebay for around £5) driving a 35mm prop with 7.6v of NiMH gives a sparkling performance for these light boats. I think that a 1.5cc diesel would be rather over-egging the power – a 0.5cc diesel would make one go pretty fast…
Edited By Dodgy Geezer on 30/12/2015 16:42:46
Edited By Dodgy Geezer on 30/12/2015 16:46:07