Ma-Sea Solar boat

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Joined: 08/11/2016
Location: Australia
Posts: 814
Posted: 02:17am 22 Feb 2018      

Not too shabby, I get about 35 by the gps with 25hp on a 4.2m glass hull flat out- but it empties the (little) tank in about an hour doing that, cutting it back to 1/2 power I get about 20kmh but over 2 hrs -nearly 3...

Its a heavy boat tho, right at the limit for a unbraked trailer when it had the big inbuilt tank filled right up, dont use that tank atm as it has a leak and puddles fuel at the back next to the motor, not good

So you're getting pretty good speed out of it, have you weighed it yet?



Joined: 15/07/2006
Location: Australia
Posts: 497
Posted: 08:03am 22 Feb 2018      

Thanks for your input Boppa. I was wondering, how do I compare to a petrol outboard. I want to run a 20HP petrol on this boat to compare but I don't want to own a 20HP petrol motor.

Yes we did weigh it.
As originally made, 114kg .
With the second pontoon width added, 130kg.
Golden Motor weight is 50kg.
Lithium batteries, 48v (16 cells) x 100Ah-B, plus box, 72kg

The Golden Motor is 10kW. At 52v x 189A = 9828W. My conversion makes 10kW to be 13.4HP. But they say it has the performance of a 20HP petrol.
Trev @


Joined: 08/11/2016
Location: Australia
Posts: 814
Posted: 08:20am 22 Feb 2018      

Comparing outboards in hp is always misleading as so much depends on things like prop pitch, revs etc that its hard to directly match HP to speed.

A mate of mine had a 50(I think) hp motor that had been fitted by the previous owner with a racing/ skiing prop, he replaced it with a 75 stock, and actually went slower. Many manufacturers fit a prop that will peak below redline, so much so that many can never actually get to their redline. This is a good idea in one sense as many outboards dont have instruments on them, and many boat owners simply run 'flatout', so setting up the motors in this way stops people blowing their motors up

I have a little 78lb electric trolling motor that came with two props- one is a hard plastic jobby that gets about 5kmh, the other is a floppy 'jelly' prop, meant for mangroves etc, same size, same pitch, but only makes 2kmh (due to its bending I suspect)- it really is 'floppy' and you can bend the tips back to the hub!



Joined: 15/07/2006
Location: Australia
Posts: 497
Posted: 10:49am 06 Mar 2019      

We received some new design outboards from Golden Motor.

Kerme has been sitting under the tree since we had it in the water back in February last year. It has faded a lot and was very dirty. Had to put the gernie over it and scrub it with brooms. It really looked neglected for a long time.

Fitted up a new motor.

The new motors are adjustable in leg height. Absolutely a brilliant idea. They also have heat exchanger, no sea water through the motor or controller. It takes the normal car coolant for corrosion resistance, another brilliant idea. I do like the coolant pump too, much quieter than the older design. Also for corrosion resistance, it is fitted with a zinc anode. No air through the propeller centre. The old design still had an air line where a petrol exhaust would have been, which let air through the centre. This new motor stopped the water spray up the front of the leg much better than the old design. 10kg lighter than the old design, this new outboard measured to be 40kg. The motor shaft is horizontal and runs a tooth belt to the prop shaft, much quieter running, and very smooth. Well done to Golden Motor for developing a brilliant outboard.

Some performance data
Amps Km/hr
30 9
40 10
45 11
54 12
70 13
72 15
88 17
100 18
110 19
125 20
142 21
182 23 182A was full throttle.

We lowered the leg a little bit, and achieved 24km/hr at 175A.

Trev @



Joined: 15/07/2006
Location: Australia
Posts: 497
Posted: 12:51am 03 Dec 2019      

Some more changes to Kerme.
Cut out the second width pontoons. Added a V-Bottom. More planing surface and more tunnel space. A little less buoyancy though, so draft is more. Fitted 2 Golden motors.

Off to the water for testing.
It feels to skip a lot better at high speed, but the numbers don't indicate anything better. With the 2 motors, it never achieved any better speed than with one motor, but used more electricity. Pulling power is ok. Knee board was easy, and I got up on 2 ski's, but single ski could not get up.

Pack voltage at rest measured at 52.6v
6.3A      2.4 km/hr
8.3A      2.4 km/hr
13A        3.2 km/hr
28A        6.8 km/hr
35A        7.5 km/hr
48A        8.2 km/hr
56A        8.8 km/hr
78A        9.7 km/hr
120A       13.2 km/hr
128A       15.2 km/hr
148A       18.6 km/hr
185A       17.8 km/hr strange result
259A       21.3 km/hr
275A       24.0 km/hr
but later, another strange result
250A       26.8 km/hr

Trev @


Joined: 08/11/2016
Location: Australia
Posts: 814
Posted: 05:40am 03 Dec 2019      

I suspect you are running out of revs rather than power...
Certainly sounds like it- if the revs is the limiting factor, then it really doesn't matter how many motors you had, you would still have the same top speed, just faster acceleration and more 'towing ability' (you could put a dozen motors on there and still have the same top speed if this is the case)

In a normal IC outboard motor you often have the same issue, which is why 'racing props' are available- they trade acceleration for top speed with a different pitch angle (they do have drawbacks, both acceleration and slow speed suffers, and taken to their extremes, can allow an ICE motor to over-rev, making for an expensive 'bang' moment lol)



Joined: 15/07/2006
Location: Australia
Posts: 497
Posted: 09:55pm 11 Dec 2019      

Got 2 new propellers. 9.25 x 10. Original propellers 9.25 x 7.

Headed out to the water for another test
At rest, battery voltage measured at 53.1v. This test was heading into the wind

15.6A     6km/hr
23.3A     6km/hr
40A       7km/hr
52A       9km/hr
69A       10km/hr
88A          water sprayed up in the wind, over the bow so give more throttle quickly
170A      17km/hr
176A      19km/hr
180A      21km/hr
210A      25km/hr
225A      27km/hr
273A      29km/hr
277A      30km/hr

Screen shot the speedo after we stopped. Max at 33, but mostly could only achieve 30km/hr

I wanted to see what one motor could do on its own so lifted the other motor and disconnected the power cable. Flat out at 13km/hr. Bear in mind though this was with one motor on the side of the boat so not a direct push. steering turned to get boat to track straight.

Trev @



Joined: 15/07/2006
Location: Australia
Posts: 497
Posted: 12:41am 15 Jan 2020      

Another set of propellers. 9.5 x 13. Stainless steel. There is not a lot of visual difference between the 9.25 x 10 and the 9.5 x 13.

Made some changes to the steering setup. We now have a temporary forward control.

Numbers for the stainless steel props. Probably not what they should be. The cav plate was borderline with the smaller props. With the slightly bigger diameter stainless steel props, they cavitated a little. Achieved similar speed with less amps.

15A    6km/hr     Planing at this speed
31A    7km/hr
45A    9km/hr
50A    10km/hr
70A    11km/hr
100A   16km/hr
120A   18km/hr
160A   20km/hr
170A   25km/hr
200A   28km/hr
250A   30km/hr
256A   31km/hr     Max throttle could only get 256A

The highest speed we saw was 31km/hr, but mostly could only get 30km/hr max.

Here is a comparison of the 3 propellers

Edited 2020-01-15 10:47 by Trev
Trev @



Joined: 31/12/2016
Location: Australia
Posts: 658
Posted: 02:40pm 15 Jan 2020      

Hi Trev,

Have been watching your progress.
I used to build Aluminium boats, never really got the chance to try one on the water, however the boss was interested in trying a new prop on the boat he had as tho old prop was worn.
Now with the good new prop at full RPM (old 2 Stroke motor) it managed 53kmh, then after that we tried a larger prop and then found the motor could not reach full RPM I think it was a little slower too, can't remember it was long ago, Extra friction may also have been a factor.

If you are getting speed with the new prop and lower amps I think you are on the right track.
Also do you know what rev's the motor is doing? I suspect it has reached its maximum rpm with that SS prop, hence the lower current at that speed, If I read this correctly.

Nice work BTW.
Cheers Aaron
Off The Grid



Joined: 15/07/2006
Location: Australia
Posts: 497
Posted: 02:38am 05 Apr 2020      

Several weeks ago we changed back to 1 motor. And went out to the dam for testing.
Had to cut the transom / motor mount down so the cavitation plate would be below the bottom of the V-Bottom. There is less boat draft at rest, but with the extra 100mm cut out of the motor mount to get is low enough, bring the motor about the same height to the water level as the 2 motors, mounted higher, but weighing down deeper draft.

I need more buoyancy, to reduce the draft.

We tested all 3 props on this single motor and boat configuration.No significant difference with the 3 different props.
The first column is speed,km/hr, then under each prop size is the current (amps) at that given speed. Of course my measurement reading is probably not all that accurate, but gives an idea of what is happening.

Edited 2020-04-05 12:45 by Trev
Trev @

Old Seagull Man
Regular Member

Joined: 21/12/2019
Location: Australia
Posts: 47
Posted: 03:51am 05 Apr 2020      

Hi Trev.

Excellent project, did you get the motor from an Australian seller, or directly from Golden Motor?
I'm interested in buying one of there L05

 motors and the is a paypal option, on their wed site. It would be perfect for my old  20foot banks dory..



Joined: 15/07/2006
Location: Australia
Posts: 497
Posted: 07:47am 17 Aug 2020      

Sorry Old Seagull Man. I didn't see your message until now.
I am an Australian seller. I buy direct from Golden motor.
Email me direct if you are interested in sourcing something.



Joined: 15/07/2006
Location: Australia
Posts: 497
Posted: 02:50am 12 Nov 2021      

It is around a year and a half since testing.

Kerme has been cut up.

And re-modeled. I won't go into all the details of the fibreglass work, but we have cut a lot of weight out, and used much lighter foam for buoyancy. The floor is above waterline and no space for water to catch in the boat. No need for pump. Any water runs out for itself. Basically it is a floating cork. Around 70kg for the hull.

The battery pack is 48v 100Ah. Around 50kg.
The first test is with the pod motor L10, 22kg. And 2 people, add another 120kg. Total weight on test around 262kg.

Here is Kerme with the L10 pod motor in action.

The data numbers
km/hr     Amps
 4         3
 5         8
 6        11
 7        15
 8        23
 9        32
10        40
11        53
12        66
13        68
14        77
15        90
16       104
17       107
18       108

Also measured distance traveled during testing, 2.02km and used 24Ah. Of course this is not all that relevant as the speeds were all varied.

Then was the test on the 20hp motor, 40kg. Total including 2 people 280kg.

There is a few gaps in the data numbers. The water was very rough with strong wind that day. We did the testing cross wind to avoid the wind hindering or helping. The choppy water didn't help either. Don't know why but could only get 158A on that day.
km/hr     Amps
 5         6
 6        13
 7        23
 8        35
 9        37
11        66
12        73
14        76
17       100
24       158

In comparison

1) Original shape. 114kg plus .. Total 346kg. No performance numbers. This is like a bath tub. But still can't sink. Floor is above waterline with self drain holes.

2) With the second pontoon width added, 130kg plus .. Total 362 or 372kg depending which motor. Max speed 24km/hr with 191A. With motor height adjusted a little, got 25 km/hr 189A.

3) With v-bottom tunnel and single width pontoon. Probably still 130kg plus .. Total 362kg or 372kg But I don't think I tested the heavier motor on this configuration. Achieved 24km/hr at 175A.

4) No comparison drawn with the twin motors.

5) New Kerme shape and weight has resulted in some better efficiency, 24km/hr with 158A. Top speed should be higher but don't know why it didn't give more amps.
Edited 2021-11-12 12:52 by Trev



Joined: 15/07/2006
Location: Australia
Posts: 497
Posted: 02:52am 17 Mar 2022      

Kerme gets the solar panels.

I bought Sungold flex solar panels (whole pallet) quite some time ago (years) with this idea in mind (and also as a business proposition). However, a high number of these panels sold to customers have returned. They don't last and Sungold factory won't honour their original warranty terms. They told me 5 year warranty, but many panels are not lasting even 1 year. My brother is one of those customers. I decided to keep him as a test pilot of these panels. He is up to 5 or 6 replacements now. I needed to put up some panels for charging an electric quad, so decided to mount some Sungold on alloy (better cooling) because most returned panels were sikaflexed on surfaces without cooling.

They have 5 year warranty on their old and new website

Then several emails stating 25 year warranty. They can't be trusted.

Here is a picture when installed for charging the electric quad, 9 April 2021. They are fixed with screws, no glue.

Here is a picture I have taken just now, 17 March 2022. One is obviously failing, not quite 12 months.

They are still charging, but not as much as they should, or did when first put up. I have seen as high as 3.2A, but should be 6A or just over 6A.

Anyhow, just needed to give a little history on these panels. Kerme gets 8 of these Sungold panels (140W each) as another test run. Sure have to keep a good eye on them before each trip out to sea. It will be a real bugger not being able to get back to land.

Kerme also gets 4 of the Symmetry panels (110W each). We will see which panels last the longest.

Edited 2022-03-17 13:53 by Trev

Senior Member

Joined: 26/09/2020
Location: Australia
Posts: 183
Posted: 09:26pm 17 Mar 2022      

Next step may be to fit it with hydrofoils. The Manly ferries used to do well with them when they were running on Sydney harbour.
It would reduce drag a lot and you should be able to get a fair bit more range.
Maybe look at those surfboards that are being used with winged keels under them to lift them out of the water.
Anyway looks like you are having fun, that is the best thing to do in life.



Joined: 15/07/2006
Location: Australia
Posts: 497
Posted: 03:11am 30 Mar 2022      

Yes occasionally we used to ride the hydrofoil (or slow ferry) from Circular Quay to Manly on a Saturday night and eat ice cream and wait for the last ferry back. That's when we were young and silly. Once they cancelled the last ferry!

First day for charging.

The battery pack was empty, most cells were discharged down to 3.0v, or something like 48v for the pack. After being parked in the sun all morning, the pack voltage now in midday sun is 54.2v.  

Back set of panels. Sungold 140W x 4 series. Midday sun 5.6A

Middle set of panels. Sungold 140W x 4 series. Midday sun 5.5A

Front set of panels. Symmetry 110W x 4 series. Midday sun 5.4A.

Sungold are not really any better than the smaller wattage Symmetry. Symmetry are also smaller size, so with this roof area, I could have 4 sets of Symmetry, but only 3 sets of Sungold will fit.

Total charge in midday sun is 16.8A

So far have put in 58Ah. I will update on anew post how many Ah I get for the day.

Temperature is generally around 38 -42 degreec C. But one point I did measure 48 degrees C.



Joined: 15/07/2006
Location: Australia
Posts: 497
Posted: 07:04am 30 Mar 2022      

The internal clock started yesterday after noon when I connected the battery. 102Ah in over the 24 hour period. Another 6Ah in after the clock changed to the new day, to get the battery full again. The battery size is 100Ah. Still have sun available, but the shadows are getting longer.



Joined: 15/07/2006
Location: Australia
Posts: 497
Posted: 03:00am 01 May 2022      

An update on the Sungold flex panels on my roof for charging the quad bike.
That failing panel, has failed.
I noticed last week sometime when I plugged in the quad bike for charging that it didn't charge. I didn't have time to investigate until today.

Battery voltage 53.2v. Solar voltage 52.0v. So zero charge.

Check the panel

Replaced the failed panel, and we get charge again.

So If I take today as the fail date 1 May 2022 and the install date was 9 April 2021, then we are just over 1 year. That is extremely poor performance.
Edited 2022-05-01 13:04 by Trev



Joined: 31/12/2016
Location: Australia
Posts: 658
Posted: 07:39am 05 May 2022      

Thats not very long lasting at all.
I had a friend that wanted to use flexible solar panels to cover the entire roof of a Bus, this was about 8 years  ago, at the time the solar panels available were low wattage and after some research most were not Supposed to be connected in series or parallel, for those reasons we decided it was a no go.
They were intended use was for 12v battery charging, I wonder if the 1000v series rating in these panels is some what exaggerated.