Small inboard gas engine

[dskira]

Good day
It is sad we don't find small inboard engine anymore. they are smooth, easy to repair, do not need to run a long time to have the right temps like the diesel, they are light, and the risk of explosion almost inexistant if properly installed. (diesel get sometime in fire and that not fun eather)
We put gaz bottle in boat and its far more dangerous than gasoline.
I liked these gasoline engine for sail boat. I had one in the seventees a one cylinder Fita, realy smooth. They are less expensive to built than diesel, and the consumption as an auxiliary engine is not a real concern.
Well it is what I think. is sombody else agree? Just curious :)
Or perhaps somebody knows where to find a proper inboard gas engine in the 8 to 15 hp range :?:

[alan white]

I agree. I've seen people switch to diesels and then of course they have a propane stove inside the cabin.
Gas engines are smooth and I wonder why nobody ever designed a bilge blower whose flow prevented the engine from cutting out---- a simple switch activated by a flap. Then no gases could accumulate.
I had a Vire from Denmark---- reliable and smooth and it would run on kerosene. Only moving parts were piston, crank, and rod. Period.

Alan

[kengrome]

I think no one builds them anymore because they don't see a huge market for them, not with outboards being so easy to install, use, and remove in comparison. A resurgence in small inboard powered boats will have to occur before there's enough demand for a company to start making some good ones again.

I have always wondered if I should be making such engines instead of boats. My dream would be a small horizontally opposed or v-twin with a dry exhaust stack, a built-in infinitely variable planetary gearbox, and some kind of mechanism that allows the prop shaft to be installed at any angle without changing the engine's position -- perhaps a CV joint or something similar. Then installation would be super-simple with all of the difficult alignment issues virtually eliminated.

I think it is realistic to believe that such a design is possible, but it might take a lot of time and money before prototypes are built and tested then a factory setup and ready for production. Environmental regulations make designing simple engines 'more difficult' these days too, so they will never again be as simple as the old ones were. That's really too bad too, because the simpler they are the more reliable they are.

[alan white]

Gas engines are very light in comparison with diesels. For this reason (and the current acceptance of outboards), it would be nice to see an electric motor like a Briggs and Stratton Etek as the driving motor and a small compact gas genset as the provider of electricity. The electric motor requires no gearbox, being reversing and high torque (the Etek R or RT model is a high torque version).
The motor weighs 22 lbs or so.
The genset could be a suitcase unit on deck, inside of a fiberglass or plastic case mounted in the rear of the cockpit. Its throttle could directly increase/decrease wattage and hence speed so batteries could be taken out of the loop if desired.
The genset would be easily serviced or replaced while the electric motor would need little if any attention ever.
88% efficiency, ultra reliable, constant 8 hp with 15-19 hp on tap for short spurts (using a battery), short trips without the genset running (using a few batteries), opportunity for solar and wind assist.

Alan

[TollyWally]

Ken,
I would think that the gearbox is the challenge. . Our asian friends have filled the world with small well built motors, not so many gears. Built in has advantages but so has an independant installation when it comes to service and repair.

[TollyWally]

Alan,
The original premise of diesel electric was, I believe, just as you pointed out all about solving the gear problem. But, correct me if I'm wrong, won't you get less propulsion thrust per gallon of fuel consumed by running it through a genset and then an electric motor than burning it directly in an engine/gearbox setup ?

[alan white]

Alan,
The original premise of diesel electric was, I believe, just as you pointed out all about solving the gear problem. But, correct me if I'm wrong, won't you get less propulsion thrust per gallon of fuel consumed by running it through a genset and then an electric motor than burning it directly in an engine/gearbox setup ?

No, as a matter of fact, the high efficiency of the electric motor, and in eliminating gears (running a straight shaft with a low RPM per volt motor) coupled with an efficient genset (which allows the gas engine to run at an optimum speed if using batteries) means a distinct advantage for the hybrid set-up.
The hybrid would probably use less gas, in other words. Not only would solar and wind become options, but if there were a number of batteries, most maneuvering could be done in silence and if the gas engine broke down, there would still be ample stored power to get somewhere.
The maintenence would be easier as well, as the electric motor needs none and the genset could be taken ashore. No water exhaust or cooling issues, no crawling into tiny spaces to fix things, no fire hazard.
The electric motor would be about 8 inches around and maybe 4 inches thick--- therefore further back and allowing the engine area to become valuable storage space for example.
Vibration would be lessened too, since the vibrating item (engine) isn't any longer transferring power through the hull.
The "suitcase" genset could be of less hp than the electric if batteries were used. A 2500 watt unit putting out 72 volts would be ideal, allowing 92% efficiency from the motor. That would require only a small (3 1/2 hp) engine. The genset weight would be low, maybe 75 lbs. Being so light, it could be mounted off the stern as an outboard would be. It's generator could double as a starter. Retrofitting would be easy. Replacing the engine would be under $300.00. Overall costs would be no more than a diesel replacement and probably cheaper.

Alan

[TollyWally]

Discounting additional input from solar and wind generation, if I am understanding you correctly the suitcase genset and electric motor would be more efficient in providing propulsion?

[kengrome]

The electric motor would be about 8 inches around and maybe 4 inches thick--- therefore further back and allowing the engine area to become valuable storage space for example. Vibration would be lessened too, since the vibrating item (engine) isn't any longer transferring power through the hull.Ideally the electric motor would be engineered with a hollow tube type shaft instead of a solid shaft, with clamps on each end that tighten onto the prop shaft. Simply slide the motor onto the propeller shaft then clamp it on tightly (a spline would work too of course although at additional cost and probably not necessary). The motor's outer casing can then be secured to the hull via flexible mounts to cushion the starting and stopping torque and isolate vibration from the hull.

[Rick Willoughby]

Gas engines are very light in comparison with diesels. For this reason (and the current acceptance of outboards), it would be nice to see an electric motor like a Briggs and Stratton Etek as the driving motor and a small compact gas genset as the provider of electricity. The electric motor requires no gearbox, being reversing and high torque (the Etek R or RT model is a high torque version).
The motor weighs 22 lbs or so.
The genset could be a suitcase unit on deck, inside of a fiberglass or plastic case mounted in the rear of the cockpit. Its throttle could directly increase/decrease wattage and hence speed so batteries could be taken out of the loop if desired.
The genset would be easily serviced or replaced while the electric motor would need little if any attention ever.
88% efficiency, ultra reliable, constant 8 hp with 15-19 hp on tap for short spurts (using a battery), short trips without the genset running (using a few batteries), opportunity for solar and wind assist.

Alan

Alan
These motors spin too fast for best result with direct drive - something like 70rpm/V. The numbers for typical displacement speed favour at least 3:1 reduction to get good prop efficiency. The Perm PM132 might get away with 2:1 as it has higher rated torque.

If you use a PMDC motor then the brushes will require maintenance. Typical brush life I can find is around 1000hrs based on automotive applications. You could expect better in a boat but I would not regard as maintenance free. The PMAC motors eliminate the brushes.


Rick W.

[FAST FRED]

For the smaller boat GAS is ideal.

Honda and others make Rototiller replacement engines (8 to 12hp) that hace a fine usually 6-1 reduction gear built right in.

This will allow a tiny engine to replace a much larger engine.

Nicest I have seen was an old atomic 4 replaced with the tiller unit , and it still did better than 5K!.

At idle speeds the boat goes very slow , so the lack of neutral or reverse is OK.

Cruise is at Full bore! , but these little Hondas don't seem to mind.

A 4 inch duct with an inline fan did the cooling.

Only downside is with an alternator mounted on the boat must be underway to charge the batset.

FF

[alan white]

Alan
These motors spin too fast for best result with direct drive - something like 70rpm/V. The numbers for typical displacement speed favour at least 3:1 reduction to get good prop efficiency. The Perm PM132 might get away with 2:1 as it has higher rated torque.

If you use a PMDC motor then the brushes will require maintenance. Typical brush life I can find is around 1000hrs based on automotive applications. You could expect better in a boat but I would not regard as maintenance free. The PMAC motors eliminate the brushes.


Rick W.

Could be the Perm motor is higher torque (they claim 40% higher), Rick. B&S has the new high torque model as well, but I haven't researched it. I'm building an ultralight three-wheeled car right now so I'll very soon be choosing and buying a motor. Of course, I'd have a chain drive, so ratios are going to be easy to get.
The B&S have brushes, yes, but 1000 hrs is practically a lifetime aboard a small cruiser and then when it's time, how long could the job take? I suppose it all depends on the architecture of the boat.

Alan

[alan white]

Discounting additional input from solar and wind generation, if I am understanding you correctly the suitcase genset and electric motor would be more efficient in providing propulsion?

If you research state of the art technology in motors and generators, high voltage (72v) permanant magnet motors and generators are around 9o% efficient (90% x 90% = 81%, batteries account for a small variable depending on many factors).
The real savings is in the engine controls. Every engine has an RPM range where it produces the most power relative to fuel consumed. The engine is run only at this specific RPM, and is not tuned to accellerate (soft start instead). No momentary loads need effect it.
I can get amazing mileage out of a car by maintaining a steady 30 mph for hundreds of miles on level pavement. If I could lean out the fuel mixture while doing this, I could probably get over 50 mpg (or better) with my Toyota truck.
The suitcase genset would have that dead level "road" and special tuning each time I turned it on.
My guess is the efficiency of a well conceived hybrid is a bit better for those reasons. Costwise, I'd say economies of scale prevent the hybridization of small boats from competing fairly against the likes of Yanmar, for example, so while you could build your own system for about the same cost today, a manufactured system would be a lot cheaper down the road. Installation is knocked down to a fraction and parts and pieces such as controls and plumbing that would normally be required as part of a normal engine installation would be nonexistent (water intake, discharge, muffler, engine beds, cables, rods, fan, sensor for gas, through-hulls, etc.).
Long term costs involve on-site work only with straight diesel/gas, but the suitcase would have a multi-pin connector and a fuel line (with fixed onboard tank).
It could be delivered to a shop having guaranteed qualified personel. Or you could take it home, like a small outboard, and work on it there, running it at the bench.

Alan

[alan white]

For the smaller boat GAS is ideal.

Honda and others make Rototiller replacement engines (8 to 12hp) that hace a fine usually 6-1 reduction gear built right in.

This will allow a tiny engine to replace a much larger engine.

Nicest I have seen was an old atomic 4 replaced with the tiller unit , and it still did better than 5K!.

At idle speeds the boat goes very slow , so the lack of neutral or reverse is OK.

Cruise is at Full bore! , but these little Hondas don't seem to mind.

A 4 inch duct with an inline fan did the cooling.

Only downside is with an alternator mounted on the boat must be underway to charge the batset.

FF

That brings up another point. Since an electric motor drive can function as a generator while sailing, those who sail a lot more than motor need no genset at all. Just batteries and a controller. But imagine the flexibility using wind, solar, genset. and sail power (not to mention shore charging).
Shore charging is underrated, but grid power is CHEAP. Electric cars, for example, cost a fraction to run (though lacking range).

Alan


Alan

[TollyWally]

When I think of suitcase gensets I usually picture one of the Honda units, very quiet nice little units.

Is this similar to what you are thinking about?

I don't know the rating but I have twin 4D batteries, how much more capacity is needed for manuevering and in harbor work?

[alan white]

When I think of suitcase gensets I usually picture one of the Honda units, very quiet nice little units.

Is this similar to what you are thinking about?

I don't know the rating but I have twin 4D batteries, how much more capacity is needed for manuevering and in harbor work?

Imagine one of those units putting out 48 or 72 volts, with insulation to reduce noise, hung off the stern in a neat box.
Any calculation would include variables such as hp or kw required (a thirty foot boat could require an average of anywhere from 3 to 15 for harbor work depending on displacement. If, say, your average is 5 hp, that's about 3.7 kw.
With two batteries, you can get 24 volts, and so dividing 3700 watts by 24, Your amperage requirement is 154 AH. At that rate, the average set of 80 AH batteries will be depleted in an hour.
Better to istall six batteries and run 72 volts, which is higher efficiency (maybe 92% for the motor) and can use smaller cables as well.
That will give you three hours at a decent speed of say 5-6 kts.
Recharging would take maybe 5 hours if the genset puts out about 3.5 hp.
Or, the genset can run the motor direct and you'll see about 3 hp output at the prop for a speed of maybe 4-4.5 kts continuous.
The bigger the battery bank, the more voltage options, the longer the run time at higher rates, the greater the weight, the longer charge time.
I think four batteries is a good start for a small (3000#) cruiser that just needs to motor for steerageway or harbor work up to the mooring. A 6 hp continuous rated (15 hp max) motor would be fine, and a 2500 watt 48 volt genset. The controller could be a 300 amp max unit, which would allow 30 second spurts at up to 15 hp in emergency use.

Alan

[dskira]

Hi Fast Fred,
The rorotiller engine is quite a good idea.
By the way thank you all for your very enlighted comment. You gave a lot of ideas to work with.
The small genset and electric motor is quite also a great solution.
Diesel is so overprice and not as efficient we can think, there life is around 5000 hours against 2000 hours for the gas, but the price is almost five time. A rototiller engine 12 hp is around $800, a diesel is $7000, for marine use, $5000 bobtail configuration.
Perhaps sombody has better infos about pricing, it is what I see around, and I admit without going in to deep in details. But I like gas, so silent, light, smooth, and it's like sailing without sail.
Kengrome, perhaps you can take apart an outboard and reconfigure all the element in a different position making them an inboard. It will be a cheaper start. I just tossed an idea without real knoveldge.
Daniel

[Rick Willoughby]

Could be the Perm motor is higher torque (they claim 40% higher), Rick. B&S has the new high torque model as well, but I haven't researched it. I'm building an ultralight three-wheeled car right now so I'll very soon be choosing and buying a motor. Of course, I'd have a chain drive, so ratios are going to be easy to get.
The B&S have brushes, yes, but 1000 hrs is practically a lifetime aboard a small cruiser and then when it's time, how long could the job take? I suppose it all depends on the architecture of the boat.

Alan

Alan
I bought two Mars PMAC motors and 100A continuous, 48V controllers from Kelly controls. Apart from an error in their connection diagram for the hall sensors the motor works brilliantly. I have not yet tried in regeneration mode but it should not be any problem.

http://www.kellycontroller.com/

Kelly offered the best overall price including delivery cost. Both motor and controller were also best price I could find.

The combined motor controller efficiency is 88%. The controller takes 60mA at rest so I just make a mechanical connection when I start up. I have not even bothered with a fuse because I am only using small batteries for testing and they give out around 15A. The main wiring is good for 200A and I believe the controller has a fuse on the input circuit.

The wiring is more complex than a PMDC set up and quite fiddly but you need a 4 quadrant drive to give contactorless reversal using the PMDC. You also have to contend with brush life.

I found Kelly gave excellent service and support but may not have your selected controller on the shelf and this could delay by a week or so. I got one controller in a week and the motors and second controller came two weeks after.

Rick W.

[alan white]

Alan
I bought two Mars PMAC motors and 100A continuous, 48V controllers from Kelly controls. Apart from an error in their connection diagram for the hall sensors the motor works brilliantly. I have not yet tried in regeneration mode but it should not be any problem.

http://www.kellycontroller.com/

Kelly offered the best overall price including delivery cost. Both motor and controller were also best price I could find.

The combined motor controller efficiency is 88%. The controller takes 60mA at rest so I just make a mechanical connection when I start up. I have not even bothered with a fuse because I am only using small batteries for testing and they give out around 15A. The main wiring is good for 200A and I believe the controller has a fuse on the input circuit.

The wiring is more complex than a PMDC set up and quite fiddly but you need a 4 quadrant drive to give contactorless reversal using the PMDC. You also have to contend with brush life.

I found Kelly gave excellent service and support but may not have your selected controller on the shelf and this could delay by a week or so. I got one controller in a week and the motors and second controller came two weeks after.

Rick W.

Thanks much, Rick. I'm welding up the aft end of the vehicle now and so the bracket for the motor needs a motor to fit everything in correctly.
Then I'll be broke for a while but I'm going to bookmark and research Kelly.
I'm a bit slow when it comes to wiring and electronics in general.
I may bug you for some support when the time comes.

Alan

[Rick Willoughby]

Thanks much, Rick. I'm welding up the aft end of the vehicle now and so the bracket for the motor needs a motor to fit everything in correctly.
Then I'll be broke for a while but I'm going to bookmark and research Kelly.
I'm a bit slow when it comes to wiring and electronics in general.
I may bug you for some support when the time comes.

Alan

Alan
The plug used to connect the control wiring requires a small soldering iron with a fine tip. I soldered the wire and then placed heatshrink tubing over the individual cores. It was finer work than I have done in quite a while. It tests my aging eyes and unsteady hands.

I have not found a supplier of the ideal multicore cable either. In years past I used Dekron cable but have not been able to find a local supplier of this. It is these things that cause a bit of frustration. The heavy conductors and lugs were easy to get. I also purchased a new heavy duty crimper as I expect I will be doing a reasonable amount of heavy duty wiring.

Rick W

[alan white]

Incidentally, Rick, I think I am going to be adding another motor (so I'll have two) and a total hp for accelleration of about 38 hp.
I would therefore need an oversized controller to begin with in anticipation of the load of maybe 600A or more. The machine should weigh, all up, about 700 lbs, so it ought to accellerate briskly with the two motors.
I see that the controllers shown are priced in dollars, but I couldn't see if those were American or Australian dollars. Where's the company based?

[alan white]

Alan
The plug used to connect the control wiring requires a small soldering iron with a fine tip. I soldered the wire and then placed heatshrink tubing over the individual cores. It was finer work than I have done in quite a while. It tests my aging eyes and unsteady hands.

I have not found a supplier of the ideal multicore cable either. In years past I used Dekron cable but have not been able to find a local supplier of this. It is these things that cause a bit of frustration. The heavy conductors and lugs were easy to get. I also purchased a new heavy duty crimper as I expect I will be doing a reasonable amount of heavy duty wiring.

Rick W

I guess a lot of connecting and switching devices are similar if not the same part number as common industrial controls, which are always comparatvely cheap. I can solder okay. That Kelly site is a real find for me. i'm on it right now.

[Rick Willoughby]

Alan
When you deal on the web it is hard to know where the company is based. I believe I was dealing with Chinese who had perfect written english. The Mars motors are US designed but manufactured in China. The controller does not show place of manufacture. All prices are USD. AUD, CAD and USD are very nearly the same value right now so it does not make much difference.

I think all this stuff is manufactured in China and the mailing cost is lower for me if it comes direct from China. There is huge growth in electric scooters in China and I think they will soon lead with this technology. A friend working there said it is all very low cost and good value. I visited last year but did not have time to shop for such items. You can find it direct on the web but most of it requires quantity purchase.

I think Kelly are working hard to beat Sevcon and other popular controller makers.

If you use two motors then I think you would have difficulty synchronising two PMAC motors. You may be better off using the PMDC with a single controller.

Rick W

[alan white]

Alan
When you deal on the web it is hard to know where the company is based. I believe I was dealing with Chinese who had perfect written english. The Mars motors are US designed but manufactured in China. The controller does not show place of manufacture. All prices are USD. AUD, CAD and USD are very nearly the same value right now so it does not make much difference.

I think all this stuff is manufactured in China and the mailing cost is lower for me if it comes direct from China. There is huge growth in electric scooters in China and I think they will soon lead with this technology. A friend working there said it is all very low cost and good value. I visited last year but did not have time to shop for such items. You can find it direct on the web but most of it requires quantity purchase.

I think Kelly are working hard to beat Sevcon and other popular controller makers.

If you use two motors then I think you would have difficulty synchronising two PMAC motors. You may be better off using the PMDC with a single controller.

Rick W

I don't know much about the synchronization aspect. I also am considering the generating options of two motors, where the gas engine spins one motor as a generator, which allows for the omission of a 48 volt generator seperate from the motors. On accelleration, the role of generating motor would simply be reversed and I'd have both motors pulling. So maybe two controllers is an absolute requirement for that reason too. That setup also allows direct gas power at top speed.

A.

[FAST FRED]

Since an electric motor drive can function as a generator while sailing, those who sail a lot more than motor need no genset at all.

Yes BUT , (always that BUT!) to generate electric the prop will be rotating slowly under load, exactaly the formula for MAXIMUM drag from the prop.

So if you are willing to loose a K while charging at top speed and an even higher speed loss (as percentage of speed thru water) its fine.

The ocean folks I have known have all trailed small OB props hooked to very small alternators, after trying the speed brake of using the vessels prop.

IF one can put up with the unique operation of the rotor tiller engine , there is no equal in terms of costs over the boats lifetime , even with gas at $20 a gal.

FF

[alan white]

Since an electric motor drive can function as a generator while sailing, those who sail a lot more than motor need no genset at all.

Yes BUT , (always that BUT!) to generate electric the prop will be rotating slowly under load, exactaly the formula for MAXIMUM drag from the prop.

So if you are willing to loose a K while charging at top speed and an even higher speed loss (as percentage of speed thru water) its fine.

The ocean folks I have known have all trailed small OB props hooked to very small alternators, after trying the speed brake of using the vessels prop.

IF one can put up with the unique operation of the rotor tiller engine , there is no equal in terms of costs over the boats lifetime , even with gas at $20 a gal.

FF

Thanks for the thoughts. I wonder if a variable pitch prop would be an improvment.
Your point regarding the small utility engine is well taken and I appreciate the philosophy behind it. Yachting has gotten so expensive that it's bordering on the ridiculous in my opinion. With modern sniffers and fire systems, there's no reason that a gas engine couldn't be a best choice for a lot of sailors.
Air cooled machines do have to have air supplied, however. They should also have fuel pumps built in and possibly diaphragm carburators to deal with motion and heeling.

Alan

[kirtley]

I wonder what you think of this small Chinese-British joint venture gas engine:

http://www.cqwolei.com/ProductShow.asp?ArticleID=134

Do you think it would work as an inboard?

[Frosty]

But -but --its air cooled, if you really want to challenge your mechanical ability that would do it.

Sorry that should read,if you really really want to waste your time and money.

[kirtley]

Oh! Thanks for saving me the time & money!

[PAR]

I'm seeing $450 and up per KW once you count up everything (4.5 KW 72V motor, 72V/8A charger, 0-5K throttle, meter, converter, control box, cable, etc.) Priced through Kelly about $2,500. Seems fairly steep for 5.6 HP and no battery bank yet. Would this be typical currently as far as KW pricing?

In other words, lets assume a reasonably designed system, brushless motor, good charger, controller, batteries, etc. an average per KW or converted to HP would be possible. At least a range to work with. A 6 HP (4.4 KW) gas outboard is about $220 per HP ($165 per KW).

[tahia]

We are currently in the process of parting out our 1966 Ted Hood designed hand layed fiberglass mast head sloop which was powered by this fine gas inboard which still has only a little over 750 hrs. it should still offer good service for the lucky sailor who finds our sound hulll and restores this little yacht to fit condition. more info contact:thebarrys@camphost.us

[Manie B]

jeez tahia - talk about off topic - jeez this is a bit more than a language barrier