Hi everyone. I am still trying to get a correct size motor for my Seaport tug. The problem is that my two young boys run it and as you might guess they have it ' flat out ' all the time. I am using a 6v 5amp gel cel type battery and have got the motor selection down to a Graupner Speed 400. This is a direct replacement for the original ( now burnt out ) 380 size motor. There are 2 400's to choose from. 7.2v (1794) which revs to 16,400 and the 6v one (3321) which revs to 18,000. The obvious choice ( because of my battery ) would be the 6v one but i was wondering for the sake of a more relaxed engine and lower revs if i put the 7.2v version in that it would reduce the revs and the motor would not be running at it's full speed because i am only giving it 6v. I am more after long run time and good ( not fast ) speed and i do realise it is not a planing type hull. What i don't understand with this ' don't fit a prop bigger than the diameter of the motor' rule is that the tug originally came with a plastic 40mm 3 blade one, how could the original cheapo 380 motor run it? I have fitted a 3 blade brass 30mm scale type prop, new 4mm prop shaft and am open to any suggestions other than the Graupner you may have to fit a suitable 380 type motor and allso what would be the biggest size prop ( brass, 3 blade ) i could fit? You may see on the Seaport part of the forum that this will be my 4th motor in this boat, is this a record??? As i am new to this hobby the Dickie tug has taught me a lot about model boats and i am happy to learn more! Any suggestions more than welcome ,this forum has taught me a lot!! Regards, Dave.