re-using an AC generator as a motor

strantor

Joined Oct 3, 2010
6,778
prop on the boat was for a sub 3k rpm diesel reduced by about 1/2 so 1500 rpm at 10 hp shaft 1''
prop can be swapped or bent by a shop to change rpm needed some [bronze]
only old fashion shaft props will work not outboard as most are far high rpm 4 to 8k with odd hubs

problem with new tec bushless is very few used or surplus units
very small from power tools or too big from el car forklift ect
but few and no cheap ones in my 10 hp range

thought of and rejected ganged power tools like saws or a bunch of car starters
or golfcart starter/gens at 1 hp each from gas carts but need too many

have a golf cart el motor rated 3 hp 48v but endbell bit is part of a carts gear train and bearing
and size style shaft fails to match other el a/c motors so like my gen unit is useless lacking an endbell and bearing
So I'm on the same page, this will be outboard (motor under water) but using an inboard style prop for convenience, right? Or is it an inboard application where you just need to couple some kind (any kind) of motor to an existing shaft?
 

MisterBill2

Joined Jan 23, 2018
17,875
Moving a 25 foot sailboat at any speed is going to require a fair amount of power no matter what. And it seems like the intent is more than just using the motor to exit the marina. And a 100% efficient 10 HP electric motor of any kind will need 7600 watts in to deliver 10HP to the prop.And for an hour cruise tat is 7600 watt-hours. So now a study of watt-hour capacity versus battery size, weight, and cost, is in order. And I used 100% efficiency to make the numbers easy, "your results will vary."

So now my next suggestion is a smaller brushless motor, perhaps one HP, with a few different speed settings, and the AC generator system with a very quiet exhaust system. Probably it will need a different prop as well.
 

LowQCab

Joined Nov 6, 2012
3,956
Also,
most Sail-Boats have a "Displacement-Hull" design.

Displacement-Hulls have a definite speed limitation where
the Power requirements for any additional speed instantly go though the roof,
and therefore, a careful balance of Prop-selection, Prop-RPM, and Engine-Horsepower is
required for anything even resembling "efficient operation".

Generally speaking, moving more water with the Prop only results in
greater "Acceleration" up to the Displacement-Hull's designed speed.

Some Tug-Boats have Engines making over ~3000-Horsepower,
but they won't go any faster than maybe ~15-MPH,
because the Hull is designed to go around ~5-MPH.
.
.
.
 

Thread Starter

nota33

Joined Jul 9, 2023
25
So I'm on the same page, this will be outboard (motor under water) but using an inboard style prop for convenience, right? Or is it an inboard application where you just need to couple some kind (any kind) of motor to an existing shaft?
motor sits in board drives a shaft stuffing box prop set up in place of the removed junked diesel

only the trollers and the 2 hp o/b el are sealed underwater motors

yes sail boats are heavy and limited in speed
other problem is motor power in bad weather wind and waves and or current
while the 2 hp will move the boat in no wind wave or current states it fails with much of any resistance
and in no case with any speed above SLOW
 

strantor

Joined Oct 3, 2010
6,778
motor sits in board drives a shaft stuffing box prop set up in place of the removed junked diesel

only the trollers and the 2 hp o/b el are sealed underwater motors
In that case disregard what I said about oil filled motors.

This is the most power in the smallest, lightest package for the most reasonable price you're likely to find.

https://www.ebay.com/itm/1656908049...k_7xsxWR-K&var=&widget_ver=artemis&media=COPY

But it requires a hefty BLDC controller that will almost certainly cost more than the motor and you'll need to budget for that too.


This one costs a little more but the controller for it is much simpler and costs less than the motor.

https://www.ebay.com/itm/2942735177...k_7xsxWR-K&var=&widget_ver=artemis&media=COPY
 

MisterBill2

Joined Jan 23, 2018
17,875
In post #42 I described the power and energy requirements for an equivalent electric drive arrangement. The battery capabilities are probably the limiting detail, aside from the cost, which also is a limiting factor. The brushless DC motor described in the attachment of post#45 could work, although there may be an issue between the motor speed/torque ability and the inboard drive prop speed torque requirements. But there is still the battery requirement, unless you go fuel cell or external generator.
It might be that adequate batteries could displace the keel weight used to resist wind tipping, but I am not at all familiar with your boat or the whole science of sail boat architecture. Others will need to comment on the practicality and the cost.
 

strantor

Joined Oct 3, 2010
6,778
Others will need to comment on the practicality and the cost.
I should state also that there are certain considerations for boats that I am aware of but don't know the specifics of. I know that marine engines cost more than car engines because they are designed to not generate any sparks, due to the confined space they run in. Sparks in the boat in the presence of fuel vapors can explode.

I assume the same restriction applies to any electric drive components in the same confined space. But does it still apply if the boat is fully electric and there are no fuel vapors, and/or the generator is mounted topside? I don't know. I leave it up to TS, as the owner/operator of this boat, to know what is safe and what isn't. My suggestions should be understood to not include consideration or complete understanding of these restrictions.

Any brushed motor (like the 2nd link in post #45) will generate sparks. Also, lead-acid batteries generate hydrogen gas when charging and should be (i think) considered just as dangerous as a vented fuel tank with regard to explosive gasses/vapors.
 

BobTPH

Joined Jun 5, 2013
8,684
I would not think that would be an issue on an electric / sail boat.

I agree that the RPM and torque might be a problem, fixable by a new prop or a gearbox.
 

Thread Starter

nota33

Joined Jul 9, 2023
25
hydrogen gas goes up quickly from battery charging so if vented not real bad
gasoline sinks as does propane so requires a vent fan to remove as it is heavy

at power of 10hp or less belts or chain drives ''work'' cheap
el reverse is a plus also if simple

most marine used motors are from small gen or tractors a few from pumps in very small unit diesels
many are low volume high priced and high parts priced 2x the tractor identical part or more
I know of none as boat ONLY designs

small gas units nonexistant in inboards all out boards now

there are a few high priced boat marketed el motors all very resent
a few older docking aids like bow thrusters
 

MisterBill2

Joined Jan 23, 2018
17,875
I should state also that there are certain considerations for boats that I am aware of but don't know the specifics of. I know that marine engines cost more than car engines because they are designed to not generate any sparks, due to the confined space they run in. Sparks in the boat in the presence of fuel vapors can explode.

I assume the same restriction applies to any electric drive components in the same confined space. But does it still apply if the boat is fully electric and there are no fuel vapors, and/or the generator is mounted topside? I don't know. I leave it up to TS, as the owner/operator of this boat, to know what is safe and what isn't. My suggestions should be understood to not include consideration or complete understanding of these restrictions.

Any brushed motor (like the 2nd link in post #45) will generate sparks. Also, lead-acid batteries generate hydrogen gas when charging and should be (i think) considered just as dangerous as a vented fuel tank with regard to explosive gasses/vapors.
Most brushless DC motors do not contain sparking brushes. And most electrical drives do not use gasoline. So fumes are much less of a hazard
 

strantor

Joined Oct 3, 2010
6,778
Most brushless DC motors do not contain sparking brushes. And most electrical drives do not use gasoline.
Is that sarcasm? If so, it's a swing and a miss.
Actually it is either way.
I will quote myself, the parts you missed:
Any brushed motor (like the 2nd link in post #45) will generate sparks. Also, lead-acid batteries generate hydrogen gas when charging
 

MisterBill2

Joined Jan 23, 2018
17,875
Not intended as sarcasm, but rather as a comment that I had suggested that the BLDC motor suggested would not present that sort of issue..
One interesting thing is that some larger US Navy ships claim to have gone to electric motor drives, of the brushless variety. Certainly using an electric motor allows more flexibility in the arrangement of a drive system.
and certainly an electric drive can be run at much less than full power, reducing battery drain quite a lot.
 

shortbus

Joined Sep 30, 2009
10,044
One interesting thing is that some larger US Navy ships claim to have gone to electric motor drives, of the brushless variety.
Better get your facts in order. Those ships are like a diesel electric train, big diesel engines driving an alternator the powering an induction motor. No BLDC motor or batteries involved.


"The US Navy has taken delivery of the USS Zumwalt, its first full-electric power and propulsion ship. GE’s Power Conversion business (NYSE:GE) was the designer and provider for the high-voltage system (HV), propulsion drive trains consisting of multiphase converters and Advanced Induction Motors (AIM) for the DDG 1000 class of futuristic destroyers."
From - https://www.gepowerconversion.com/n...s-1st-full-electric-power-and-propulsion-ship
 

strantor

Joined Oct 3, 2010
6,778
One interesting thing is that some larger US Navy ships claim to have gone to electric motor drives
Like a series hybrid? That is a bold move. Seems on the surface to preclude redundant drive methods, and the Navy loves redundancy. I'm sure they worked redundancy into it some other way

I know first hand that Navy submarines have redundant drive methods and one of them is a (huge) electric motor ultimately powered from a (huge) bank of lead acid batteries (still to this day lead acid) and entering the battery well requires a ritual involving obtaining the blessing of signature from multiple tribal leaders and shamans, checking of multiple atmospheric fortune telling devices, forced ventilation if required, and then entry only after removal of all metallic ornaments except insulated tools and one must carry the explosion proof flashlight talisman to ward off evil spirits. This is why I mention hydrogen gas. Most folks probably don't give it any thought because under a car hood there is nowhere for explosive gasses to accumulate. But a boat is meant to be water tight so it's a different situation and I continue to encourage caution.
 

Thread Starter

nota33

Joined Jul 9, 2023
25
have seen ads for the ''NO NAME '' CHINA aircooled diesels before
I even asked around other boat sites if anyone has used or seen a real one in the USA
no body has yet reported any result
I am still thinking about being a guinea pig for 500 on that bet
no idea who makes them is part of the mystery or if they are a copy of ?
 

Thread Starter

nota33

Joined Jul 9, 2023
25
Have you even Googled for a 10 HP diesel motor? https://www.google.com/search?client=firefox-b-1-d&q=10+HP+diesel+motor Far cheaper than I expected. I'd stay away from Aliexpress but have had really good luck with motors from Northern Tools over the years.
Northern tool sells GAS motors those are some of the better honda style CLONES LISTED in your link

OR I would go buy one if diesel as they are about a mile away
no idea why google lists gas motors with diesels

I am not a never china guy somestuff is ok
but spend on stuff known to be good or at least fair for the job
and fear unknown sourced units
 

Thread Starter

nota33

Joined Jul 9, 2023
25
problem on the china diesels
price is each for 5
1 is more then double the x5 price ads said 800 but 1 unit is 1650 plus 8xx shipping
and shipping is huge so the 800 per unit is over 3k for 1 shipped here
 

BobTPH

Joined Jun 5, 2013
8,684
problem on the china diesels
price is each for 5
1 is more then double the x5 price ads said 800 but 1 unit is 1650 plus 8xx shipping
and shipping is huge so the 800 per unit is over 3k for 1 shipped here
:(

Edited: I find it on Ebay for $457 quantity 1 with free shipping. :)
 
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