Marine means expensive

I bought the Prop, ‘Solas Amita 3’


It is 9 10R  which means 9 inch diameter, is for a larger HP range ~15HP to 25HP, and may be too large, but there is a smaller model available that will fit the same shaft.

How do I know if it is too big ?. I will run the motor at an ideal RPM, something that it ‘likes’ and runs efficiently at (1500 RPM). At this rpm, the boat should be going an efficient hull speed (5 knots) and not pushing too much of a bow wave. If the boat is going too fast at this RPM.. the prop is too big. I think.

The guy at the shop was helpful after he realized I wasn’t in the market for a $600 prop (what a rip off) and from what I can gather there is no standard inboard installation, and marine means expensive. I intend to use parts from the mass market : Automotive. Same quality, lower cost.  Trailer bearings and seals are looking promising for the thrust bearing. Aluminum Alloy tube for the shaft. No worries…




Motor arrived, Quicker than expected




A 10kG parcel arrived unexpectedly, and inside was this beautiful piece of machinery.
That was quick.

I notice the bearings are NSK made in Japan. I’m glad, I think the quality is good. Time will tell.

It’ll be a while before I can fire this up.




Motor is ordered, batteries to follow

I have ordered the motor from GoldenMotor com..

It’s a HPM5000B 5kWatt, 48V with liquid cooling, a modest $600 including shipping.

I bought some electric bike wheels from these guys 10 years ago and had no problems, they were quite good. These motors really are quite simple,, as long as it has decent bearings I expect to get reliable life and ‘Monstrous’ power’ ! from it.


I have the Boat hull already,..and I took it for a drive with the original Outboard motor.. The trip reminded me why electric motors are great.. The petrol motor died a few times, (It is an 80s model Evinrude) and I had to battle wind and sand banks while trying to start it.. giving it choke, too much choke flooded a little bit..not enough choke. I swore at it more than once.


These will be Lithium Ion (Life) batteries, the latest and greatest.

A bank of 12, with a custom battery management system.


Also custom: A BLDC sensorless driver designed by me, specially for electric boats;

– Gradual speed ramp up,

– quick cut-out on over current (when prop jams on a sand bank or log)

– Sensorless (extra reliable)

– simple control: one switch for direction,  One Button speed control and stop.


that’s all for now, I’ll see how this new blog looks..