Switched to Electric

Fah Kiew Tu

Curmudgeon, First Rank
10,081
3,249
Tasmania, Australia
You obviously have never owned a 2hp four stroke Honda outboard.   :D

(which is really strange because we own several other Honda products and they have always been the definition of reliable)
This. My Honda o/b has ALWAYS started in 3 pulls, nearly always on the first pull.

My GF has a Honda lawn mower. It always starts & runs.

FKT

 

DDW

Super Anarchist
6,561
1,124
My British Seagull always started on the 1st pull. After a 20 year layup it took two pulls. Then one pull after that. 

The ePropulsion electric that replaced it always starts in no pulls, which is even better. 

 

thinwater

Super Anarchist
1,041
133
Deale, MD
People can whine about how dirty/nasty two cycle outboard are, but never have I heard many complaints about old fashioned reliability.
I've had four 4-strokes and five 2-strokes.

The four strokes were better in every way except weight, INCLUDING reliability. So no, I don't believe 2-strokes have any obvious advantage, and certainly not enough to overcome their faults in most applications. The problems I've had with 4-strokes (water pump, rust-out) were not related to the issue. Same with the 2-strokes (starter, ignition, failure of non-ethanol parts on a really old motor that was done in anyway).

Either will be equally reliable if you feed them clean, dry gasoline.

There. Log that.

 

thinwater

Super Anarchist
1,041
133
Deale, MD
It took me 4-pulls last time out. Of course, it had been a while and it was 34F. Only one lazy pull on the way back in a few hours later.

 

Kenny Dumas

Super Anarchist
1,221
464
PDX
My 4600 lb 32’ does about a knot with an 80 lb thrust MinKota on 12 volts ~30 amps (360 watts ~0.5 hp).   Just in case someone wants to plot the power - displacement- speed curves and wants a useless zero intercept data point. 

 
Many zealots in the electric boat business simply overstate the power output of their product. Call it lying, marketing puffery, whatever, it is simply not true. Net SAE, JIS, and DIN output includes everything on the engine (but not the transmission). At the same time, many electrics are being advertised on input power, not output, and they are only about 90% efficient. 

 Electric power is a great idea. Sell it and love it for what it is, not what it isn't. 
The weird thing is: When installed and in use, a MUCH smaller electric motor is identically effective as a much larger diesel engine. My 10KW ElectricYacht motor, that I govern to a maximum draw of 4.5KW due to the 1C discharge limit of my battery bank, moves my boat at exactly the same speed -- 6.3 knots -- as did the "3GM30F" I removed. So in actual use, 4.5KW electric motor provides exactly the same propulsion as does a "30hp" diesel running flat out. Same prop, shaft log, shaft, strut, and of course boat. 

 

Santanasailor

Charter Member. Scow Mafia
1,357
707
North Louisiana
This. My Honda o/b has ALWAYS started in 3 pulls, nearly always on the first pull.

My GF has a Honda lawn mower. It always starts & runs.

FKT
Our Honda generator, most reliable gasoline powered piece of equipment I have ever owned, our Honda Lawn mower, runs and runs and runs, you’d think it was related to the Everready bunny.  But that darned outboard, one of the happiest times of my life was seeing it leave the place, sold for 1/8 the price I paid for it, told the new owner every issue I had with it, he said ok and was happy and I was joyous.  

 
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Fah Kiew Tu

Curmudgeon, First Rank
10,081
3,249
Tasmania, Australia
The weird thing is: When installed and in use, a MUCH smaller electric motor is identically effective as a much larger diesel engine. My 10KW ElectricYacht motor, that I govern to a maximum draw of 4.5KW due to the 1C discharge limit of my battery bank, moves my boat at exactly the same speed -- 6.3 knots -- as did the "3GM30F" I removed. So in actual use, 4.5KW electric motor provides exactly the same propulsion as does a "30hp" diesel running flat out. Same prop, shaft log, shaft, strut, and of course boat. 
Conclusion from that - the 30HP engine was far, far more HP than you ever needed or the hull could use.

A 1GM10 would likely have been adequate.

FKT

 

DDW

Super Anarchist
6,561
1,124
The weird thing is: When installed and in use, a MUCH smaller electric motor is identically effective as a much larger diesel engine. My 10KW ElectricYacht motor, that I govern to a maximum draw of 4.5KW due to the 1C discharge limit of my battery bank, moves my boat at exactly the same speed -- 6.3 knots -- as did the "3GM30F" I removed. So in actual use, 4.5KW electric motor provides exactly the same propulsion as does a "30hp" diesel running flat out. Same prop, shaft log, shaft, strut, and of course boat. 
Might have been the problem right there. Power, including horsepower, isn't an alternative fact - it can be tested, verified, and reliably depended upon. 4.5 KW is 6 horsepower. Not "electric equivalent" or "diesel equivalent" horsepower, just horsepower, with a specific definition of energy per unit time.

A boat propeller is an odd load for a diesel engine, because it absorbs only a certain amount of power at a given rpm, which is not a good match for the power output curve of a diesel. They coincide only at one point, max rpm. 

 

Sailabout

Super Anarchist
My understanding is since the 70's SAE and JIS measure net HP at the flywheel with all accessories. So no drivetrain losses, both other parasitic loads are present.  Not sure that changes the answer...
Each industry has its own std even if its an SAE one.
Try to find one for electric motors. Then try to compare with sae std from an engine.

 

MikeJohns

Member
485
133
Hobart
The weird thing is: When installed and in use, a MUCH smaller electric motor is identically effective as a much larger diesel engine. My 10KW ElectricYacht motor, that I govern to a maximum draw of 4.5KW due to the 1C discharge limit of my battery bank, moves my boat at exactly the same speed -- 6.3 knots -- as did the "3GM30F" I removed. So in actual use, 4.5KW electric motor provides exactly the same propulsion as does a "30hp" diesel running flat out. Same prop, shaft log, shaft, strut, and of course boat. 
Then the diesel was oversized for the job.   Nothing equivalent there.

RPM doesn't equate to power or fuel use either, the governor on the diesel provides just enough fuel to match the rpm you set . So it provides the prop power (plus trans. losses) and no more.

 

Panoramix

Super Anarchist
Conclusion from that - the 30HP engine was far, far more HP than you ever needed or the hull could use.

A 1GM10 would likely have been adequate.

FKT
Not sure, power is power, that's a scientific fact but the power curve is not always the same. Typically if you are trying to pull a trailer behind your car, it will be easier with a diesel engine than an equivalent petrol one as you get more torque at low rpm.

IME, often when there is a practical difference between the 3GM and the 1GM tends to be for a very short time while you are in "trouble". For instance the wind is very gusty, you slow down too much and the boat starts to go sidewise in a tight place. Or wind is pushing you hard and you need to actually stop. Also you are trying to go into the wind but the bow doesn't want to do it... Or possibly wind is pushing you against a pontoon you are trying to leave and you want the keel to "grip" ASAP. In all these situations you want to deliver a short burst of energy...

The rated power is taken at a constant rpm, it definitely is  relevant if you are trying to dig a big hole in the water with your hull but in the sensitive times highlighted above, I suspect that it doesn't tell you the whole story. Inertia of the engine or other factors might come at play.

 

johnsonjay17

Member
111
32
Not sure, power is power, that's a scientific fact but the power curve is not always the same. Typically if you are trying to pull a trailer behind your car, it will be easier with a diesel engine than an equivalent petrol one as you get more torque at low rpm.

IME, often when there is a practical difference between the 3GM and the 1GM tends to be for a very short time while you are in "trouble". For instance the wind is very gusty, you slow down too much and the boat starts to go sidewise in a tight place. Or wind is pushing you hard and you need to actually stop. Also you are trying to go into the wind but the bow doesn't want to do it... Or possibly wind is pushing you against a pontoon you are trying to leave and you want the keel to "grip" ASAP. In all these situations you want to deliver a short burst of energy...

The rated power is taken at a constant rpm, it definitely is  relevant if you are trying to dig a big hole in the water with your hull but in the sensitive times highlighted above, I suspect that it doesn't tell you the whole story. Inertia of the engine or other factors might come at play.
Theoretically the power curve can matter but in my experience the torque of a prop is less than the diesel at all low RPM's. It just doesn't seem to matter in all the real world docking I have done.

JJ   

 

Fah Kiew Tu

Curmudgeon, First Rank
10,081
3,249
Tasmania, Australia
Might have been the problem right there. Power, including horsepower, isn't an alternative fact - it can be tested, verified, and reliably depended upon. 4.5 KW is 6 horsepower. Not "electric equivalent" or "diesel equivalent" horsepower, just horsepower, with a specific definition of energy per unit time.

A boat propeller is an odd load for a diesel engine, because it absorbs only a certain amount of power at a given rpm, which is not a good match for the power output curve of a diesel. They coincide only at one point, max rpm. 
Unless of course you have a controllable pitch prop, which few small boats do any more...

FKT

 

johnsonjay17

Member
111
32
iiuc. the main problem is charging locations, not charging times. at least with the latest and greatest cars, and chargers.

LA to Las Vegas. One stop. for 15 minutes. https://www.tesla.com/en_CA/trips#/?v=MS_2020_LongRange&o=Los Angeles, CA, USA_Los Angeles Los Angeles County [email protected],-118.2436849&s=&d=Las Vegas, NV, USA_Las Vegas Clark County [email protected],-115.1398296




And shorten the life of my battery? I don't think I would do that on a regular basis. 

image.png

 

DDW

Super Anarchist
6,561
1,124
Theoretically the power curve can matter but in my experience the torque of a prop is less than the diesel at all low RPM's. It just doesn't seem to matter in all the real world docking I have done.

JJ   
Here is a typical power curve for a boat. This happens to be the engine in my trawler but they all have the same shape. The top curve is power available from the diesel at full throttle. The bottom curve is the power the prop will absorb at that rpm. There is nothing you can do about the bottom curve, except change the prop (or the pitch if variable, or transmission ratio). They meet at only one place, and that is max rpm. Everywhere else, the diesel has far more power than is required to turn the prop at that rpm, and it is prevented from accelerating because boat diesels have an rpm governor (not a throttle like a gas engine and not a torque governor like a car diesel) and the lever sets the rpm. The governor will pull back the fuel rack (or injection timing) to stay at the rpm selected by the lever. For example at 2000 rpm this engine can produce about 350 hp but the prop will only absorb 125 hp.

An electric motor will have a different power curve, but it will still be way above the prop absorption until the two meet at the top. 

A variable pitch prop allows you to move the bottom curve around some, which can result in more efficiency but usually not much. The fuel map for a modern diesel is pretty flat anywhere in the middle of the operating range. It is the prop curve that determines how much fuel (or amp hours) you burn. 

M4fyonh.jpg


 

Kolibri

Member
469
558
Haleiwa, HI
Here is a typical power curve for a boat. This happens to be the engine in my trawler but they all have the same shape. The top curve is power available from the diesel at full throttle. The bottom curve is the power the prop will absorb at that rpm. There is nothing you can do about the bottom curve, except change the prop (or the pitch if variable, or transmission ratio). They meet at only one place, and that is max rpm. Everywhere else, the diesel has far more power than is required to turn the prop at that rpm, and it is prevented from accelerating because boat diesels have an rpm governor (not a throttle like a gas engine and not a torque governor like a car diesel) and the lever sets the rpm. The governor will pull back the fuel rack (or injection timing) to stay at the rpm selected by the lever. For example at 2000 rpm this engine can produce about 350 hp but the prop will only absorb 125 hp.

An electric motor will have a different power curve, but it will still be way above the prop absorption until the two meet at the top. 

A variable pitch prop allows you to move the bottom curve around some, which can result in more efficiency but usually not much. The fuel map for a modern diesel is pretty flat anywhere in the middle of the operating range. It is the prop curve that determines how much fuel (or amp hours) you burn. 

The QT10 has a very similar governor, but it's firmware driven. I talked with the propulsion engineer about this as I was worried about the torque profile of typical electric motors relative to diesel motors. Turns out the QT10 and all of the EY motors are programmed to mimic diesels of similar horsepower when it comes to the torque profile in order to minimize the risk of damaging the shaft and prop.  

 

johnsonjay17

Member
111
32
Here is a typical power curve for a boat. This happens to be the engine in my trawler but they all have the same shape. The top curve is power available from the diesel at full throttle. The bottom curve is the power the prop will absorb at that rpm. There is nothing you can do about the bottom curve, except change the prop (or the pitch if variable, or transmission ratio). They meet at only one place, and that is max rpm. Everywhere else, the diesel has far more power than is required to turn the prop at that rpm, and it is prevented from accelerating because boat diesels have an rpm governor (not a throttle like a gas engine and not a torque governor like a car diesel) and the lever sets the rpm. The governor will pull back the fuel rack (or injection timing) to stay at the rpm selected by the lever. For example at 2000 rpm this engine can produce about 350 hp but the prop will only absorb 125 hp.

An electric motor will have a different power curve, but it will still be way above the prop absorption until the two meet at the top. 

A variable pitch prop allows you to move the bottom curve around some, which can result in more efficiency but usually not much. The fuel map for a modern diesel is pretty flat anywhere in the middle of the operating range. It is the prop curve that determines how much fuel (or amp hours) you burn. 

Thanks, you just supplied graphical proof of what I said that in my experience a diesel does not need more power at lower RPM's the diesel produces more than than the prop needs.

JJ

 

Voiled

Member
440
313
Our Honda generator, most reliable gasoline powered piece of equipment I have ever owned, our Honda Lawn mower, runs and runs and runs, you’d think it was related to the Everready bunny.  But that darned outboard, one of the happiest times of my life was seeing it leave the place, sold for 1/8 the price I paid for it, told the new owner every issue I had with it, he said ok and was happy and I was joyous.
This 1887 electric motor runs as if new, and almost silent:





Also: "you’d think it was related to the Everready bunny"

It's funny how you relate the Honda gas engine reliability to a battery powered bunny.

 
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Santanasailor

Charter Member. Scow Mafia
1,357
707
North Louisiana
2 hours ago, Voiled said:

This 1887 electric motor runs as if new, and almost silent:


Actually no.  This is a relation to our days when we were competitive slalom skiers.  You would keep going until you missed a buoy or fell.  So, we had this one lady, Ann Havard.  She would always holler out to everyone 

“BE THE BUNNY”

As In keep going and going and going. (Don’t fall) 

We lost Ann much too early.  In her early 40’s she took a short break from work, to take her little dog which she used for her clients therapy work for a walk.  

She was found dead a few minutes later.  

I miss her still.  

 
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