Good Info, thanks King;
I have the newer sine wave unit, Golden motor, and Johnson Liu exchanged the older units free except return postage, as I had installed one and it was thought to cause noise. they claim the newer complete outboards do not make noise, but I don't need one of those. I will do some insulation, a very good idea, with my water cooling it would be easier to do. Right on about the comparison between the old gas power, and the new electric. Almost anything short of a jackhammer is quieter than a two stroke 50 hp twin !!! Just that the electric noise is a higher (hair raising) pitch, more a whine – growls are easier on my ears.
I spun both motor and shaft by hand, then running the motor with foot throttle under power but not mounted to shaft was also quiet. Just when the motor gear box (fresh rebuild) is connected is it obvious, but I am beginning to think that is normal sound as an assembly. If I can fix it I will gladly post a cure for my problem. I was going to try a garden hose section, or pipe insulation foam, slipped over the drive shaft, but I got cold feet thinking about possible screw ups, maybe will do after I try everything else. The over propped thing is just what I want to address next, as I have a 12 in. by 12 pitch prop now, and the gear box is a 2 to 1 reduction. Would maybe work better with a 2 to 1 increase in speed, since torque is more than adequate.
I plan on a different prop soon, smaller sounds good. The strange part is that I still do not come close to max. amp draw while running, with floored throttle, so need more data to review as to what prop to try next. Need to tachometer the motor RPM while running on the water. I was thinking that the torque was the big problem, as the electric has way more torque than the gas power head. It does lack in RPM range however, and I would welcome a 2 to 1 gear box idea, what do you have ??
We used a direct drive to fit inside the stock cowling, but I have a complete second outboard lower unit that I would love to get higher rpm from, or maybe look at it for a small car or bike conversion. The 6 hp. donor motor lower unit is ready now for a second conversion, but the prop could not be nearly as big as on a 50 hp., so the pitch might be pretty radical, maybe a four bladed load prop ?? Not much real life data on this that I see, all boats push differently, dealers fit props depending on a lot of factors, not just motor size.
Thanks Again, Cal
Sent: Thursday, August 13, 2015 1:54 AM
Subject: Re: [Electric Boats] Re: 31' Sailboat Conversion
The noise is probably just the normal noise from that motor and controller combination, since the lower unit makes no noise when you spin it with a drill. Square wave controllers tend to make a motor run a bit more noisy than a sine wave controller. It is what it is. But if you line the original outboard cover with rock wool or something you might deaden the sound just a bit. And I bet it is still quieter than the original infernal combustion engine. I have no first hand experience with the Golden motors and controllers but my Motenergy motors with the Kelly controllers make a bit of noise. Sort of like George Jetson's car. But nothing like the old Atomic 4 it replaced!
When you say the motor spins silently, do you mean while powered by the controller, or spun by hand? When you turn the shaft by hand, it should be silent. Under power, it won't be, and under load, it will likely make even more noise, yeah. Also, when you spin the motor by hand, do you feel a definite cogging effect? This is related to some of the noise.
As for the reduction gear, typically when used in an old outboard conversion you need no additional reduction gear at all. You might want to experiment with different props, though. Your motor is probably rated for much lower max RPM than the original ICE was rated at. But a 50HP motor can turn a much bigger prop than a 6.5 hp motor can, so I suspect that you might be overpropped a bit. Just guessing. DISCLAIMER: I have not personally built an electric outboard so I might be missing something here that someone with experience converting outboards can fill in.
My reduction gear is made by Baldor and is fully enclosed, "C" face on both ends so it mounts to a standard faceplate and the motor mounts directly to the reduction gearbox. I am using 2:1 with my current motor/prop combination and of course mine is an inboard installation. My original 5kw motor is a slow wound motor and would probably work with zero reduction, but I needed a thrust bearing anyway so I used the gearbox. Anyhow it was fairly inexpensive and should last practically forever.
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