For anybody who happens to be interested I did trial on flat lake, no mast, no cruising gear and got around 4 knots (SOG gps) with Seagull forty + with clutch and weedless prop (12:30 gearbox) and also forty + direct drive and hydrofan prop (10:35 gearbox). Both at around half throttle engine not straining – extra revs did not give much extra speed
Tried hydrofan prop and also 5 blade century prop on clutch model and it didn’t have enough power
Also tried seagull century and got around an extra 0.5 knot but it wasn’t running very well (I borrowed the engine and it was longshaft)
So I’m sticking with forty + and clutch. I had a very interesting afternoon on my local pond!
This may be of interest to impecunious cruisers