donm
Active member
Late to this thread sorry.Nor me. Gadget should fit whatever engine he is comfortable with but you can reach a point of diminishing returns, 16hp is plenty, 20hp will have some reserve, that will probably never be used, 25 even more.
Gadget, As you probably well know, all boats with props labouring in an aperture tend to have two problems (at least!) 1 Prop cavitation and related noise transmitted through the hull, which is made worse as you increase the diameter/size of the prop and 2 Pressure pulses acting directly on the rudder which can become extreme even unmanageable at high revs, particularly with two blades. Before committing I would seek out people who have actual experience of motoring the Halmatic at top theoretical hull speed and see what they say. A second and third opinion is always good.
It's tempting to imagine motoring at 6.5 kts into a full gale but most people will cut the revs right down and vector off under mainsail; much easier motion, helm and noise levels.
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I have a Halmatic with a Beta 20 / 3 bladed prop. We’re in the Bristol Channel - top end with plenty of tide - and the boat has never been underpowered nor had to run on full revs. The boats are not good going astern as is well known, but I can turn her on the spot in her own length using reasonable power and prop wash so avoid going astern unless forced to do so. If the engine broke I would simply replace it with another Beta 20 in a heartbeat.
On some of the other points, I have two batteries under the cockpit sole and another in the stbd locker and have used the area below the chart table for a calorifier and a tool shelf.