Interesting...
I had something kinda' similar this weekend - went out to the boat to check on things... I have my Torqeedo 4R mounted on a C-22 now, and turned it on just to verify that the batteries were all good. The boat is not in the water, so the prop is just spinning in the air (the manual specifically states that one should NOT run the motor out of the water - so I only did it for a few seconds). The interesting part was that it hit full throttle, and the display was only showing about 250 watts - no where near the 4kw that the motor is capable of drawing.
Since there was no resistance on the prop, I guess the motor hit max rpms and just quit drawing any more power.
From: NIcholas Luker <nickluker@gmail.com>
To: electricboats@yahoogroups.com
Sent: Monday, June 3, 2013 6:09 AM
Subject: Re: [Electric Boats] Dirty prop
Being a small fantail launch thats still diesel :(
I can see the wake from the prop easily
When the props dirty the engine revs much higher and there is a tube of aerated water behind the boat at the height of the prop
As the barnacles spin off the revs drop
The engine works harder and boat speed increases
The tube of aerated water also starts to disappear
Nick
On 03/06/2013, at 11:37 AM, Dennis Wolfe <wolfeboats@gmail.com> wrote:
The critters must be affecting the blade profile and reducing its "bite" on the water. More turbulence, less thrust, less power needed to reach whatever rpm corresponds to 48v.
On 6/2/2013 9:07 PM, R&M Mair wrote:
My prop is currently got some critters attached. I notice that instead of 20 amps giving me 3.6 knots I now need 25 amps to get 3 knots. This makes sence to me. The thing I do not understand is why full throttle now tops out at 45 amps. I get a about 4.8 knots at 65 amps with a clean prop. Should I not be able to hit max draw of 100 amps with the prop like this or at least get the 65 I got before. All at 48 volts. Electric Yacht 100ibl system.
Richard
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