Took the boat out for the first time since bottom job and prop change. As expected, the results are mind-blowing. I still had the original folding sailboat prop, 12x? two blade, up until now. Two rather skinny blades. It never loaded my motor properly.
I had installed a 2:1 reduction gear and this tiny prop probably should have been run at 1:1. The highest current I saw with this prop was 65a. The highest speed was about 4kt. Usable but underwhelming. Well, I knew before I started the project that a prop change would be needed which is one reason I installed the reduction gear. First motor I tried was an ME0201014201 which is a 5kw PMAC motor, with a Kelly controller. Dropped some laundry change one day and a quarter lodged between two phase terminals, and fried the finals as well as the quarter the next time I operated the motor. Ordered a bigger controller and had the smaller one fixed as a spare. Found a good deal on a used ME0913 motor, at 12kw. The bigger controller and motor still only pulled 65a out of my 48v bank. Stupid prop. Gotta be that stinkin little prop, right? Of course. I knew that, but I just didnt have the $ for a new prop and a haulout.
So, I finally hauled out and had the bottom done. Wasnt too bad... no barnacles or oysters on the hull this time lol. Lots of slime. A few small barnies on the prop. A neighbor gave me a couple of 14x10 RH props, one chewed up a lot and one chewed up a little. The lightly chewed up one I put on the boat and dressed up with wire wheel in angle grinder, and file. The highly chewed up one went to the prop shop where for $75 I got it made like new, but now it is a 13-3/4"x10" prop. Good spare.
Splashed the boat, and ran full throttle back toward my slip. I actually pulled a wake for the very first time, with the new prop, so had to slow it down. I was definitely doing hull speed. I did not have an ammeter hooked up, as I was just moving the boat back to its home. With the boat tied down in the slip, I hooked up the ammeter and found my full throttle current to be about 130a. I say about, because it is a 100a meter. The motor is rated at 100a continuous so I wont be going there again. Weather turned to crap.. cold, windy. Finally yesterday it was spectacular. Late yesterday afternoon I disconnected my services, threw off the lines, and went for a little spin.
My $6 finest Chinese tachometer didn't feel like working. Darn. So no RPM data which I really need. I got another one on the way! I hooked an ammeter across my shunt, loaded a nav app on my android, found me a spot in the outer harbor where I could go upwind/downwind with no traffic interference, and recorded the following.
1a 1.3kt
5a 1.8kt
10a 2.4kt
15a 2.9kt
20a 3.3kt
25a 3.5kt
30a 3.8kt
60a 4.4kt
100a 5.0kt
Boat: CAL 2-27 7600 lbs 27' LOA
Infernal Combustion Engine: Nah.
Genset: Nope.
Solar: Not yet but fingers crossed.
Motor: ME0201014201 brushless 5kw
Controller: Kelly KBL48501E, 200a continuous rating with stickshift firmware installed
Battery: bank of 8 GC-2 6v golf cart batteries, 220ah, in series for 48v nominal about 10.5 kw/hr
Reduction: Baldor 2:1 enclosed gearbox
Prop: 14x10 RH 3 blade fixed
Throttle: potentiometer stuck on the end of the tiller, one knob for both speed and fwd/rev
Wind: avg about 6kt, variable
Wave action: negligible... occasional wake from passing boats.
Temp: about 65 degrees
speed is the average of upwind and downwind legs
speed is GPS SOG from my Note 3
The meter only reads to 100a so I did not do a full throttle speed run. The most interesting reading was at 1a. Amazing that 50w will move a 7600 lb boat at a usable speed! I wont vouch for the accuracy at 1a because that barely moves the needle but I guess it is reliable to +/- .5a maybe.
I dont have the data at hand for the old prop but it was definitely nowhere near as good as this big 3 blade. When I get around to it, I will stick the 12kw motor on and do a run with it. Looking forward to having a working tach again as the data is kind of lonely looking without any RPM readings.
FUTURE IMPROVEMENTS INDICATED:
Definitely considering a 3:1 gearbox with the big prop. Might look for a 16" prop but I would have to cut it down slightly for clearance. There is only about an inch between hull and blades with the 14" prop. 4 blade? I don't know. If I can get one for the same price I paid for my pair of 14x10 props, which was zero, yeah I will have to try one. Need to start on the hard top, so I can start putting solar panels up. I would love to end up with about 2kw of solar. I want to install another bank of golf cart batteries, too. 21kw/hr of storage will take me far.
FINAL IMPRESSIONS:
Pretty happy with my $2200 repower. I could never have afforded a higher tech turnkey package. Its a good match for my little $2000 boat. And tiny props suck for E-boats.
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