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Old 17-07-2019, 11:52   #1
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LPG outboard on small 30 ft sailboat

Hi all

What is your opinion about mounting an EFI LPG outboard (or old style carburateur) on a medium size sailboat?
What would be the range compared to gas given the same volume? (space available for gas tank vs a couple of LPG bottle)

Should they be more "cleaner" meaning less oily (especially i guess carburateur less dirty), less problem in general?

Thanks
Ste
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Old 17-07-2019, 12:00   #2
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Re: LPG outboard on small 30 ft sailboat

From a BTU perspective a gallon of LPG has roughly the same energy content as 1.35 gallons of gasoline. LPG is about 84,000 BTUs and gasoline is 114,000 BTUs.

Propane burns with less byproducts than gasoline.

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Old 17-07-2019, 14:56   #3
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Re: LPG outboard on small 30 ft sailboat

Yes much cleaner, longer service life, eliminate fuel going bad, ethanol issues.
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Old 17-07-2019, 15:26   #4
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Re: LPG outboard on small 30 ft sailboat

Quote:
Originally Posted by Shawn67 View Post
From a BTU perspective a gallon of LPG has roughly the same energy content as 1.35 gallons of gasoline.

That's backwards: it's actually 1.35 gallons propane = 1 gallon gasoline. In terms of locker space required it's about 2x because propane tanks are bulkier and can't be filled more than 80% full.



Any gasoline engine can be converted to propane, and I've been around many that have been, from small generators to old farm tractors to 200 horsepower Chevvy Suburbans.


Here's the tradeoff.


Propane engines are easier to start. The fuel lasts "forever" regardless of temperature. The exhaust typically has lower hydrocarbons but somewhat higher NOx: https://www.tandfonline.com/doi/pdf/....1972.10469661


The main problem with propane is fuel handling and cost. It is not practical to pour propane from one container to another, and there are fewer dealers who will fill your cylinder on the spot than was once the case since so many have switched to cylinder exchange programs. These programs usually use short-filled steel cylinders -- you get 15# of propane (sometimes less) in a cylinder designed to hold 20# -- which are unsuitable for marine use.


Usually people use the composite (plastic) or aluminum cylinders, of around 14-20# capacity (3-4 gallons). Gasoline 4-stroke motors typically burn 0.1 gallon per HP per hour at full throttle, so a 9.9 hp propane is going to burn around 1.3 gallons per hour. If you're motoring you'll have to change propane cylinders every 4 hours or so depending on the size of the cylinders and how much you open the throttle.


As with electric alternatives, this works out just fine for motoring in and out of the harbor but tends to fall down when you decide to motor up the river all day since there's no wind.
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Old 17-07-2019, 16:43   #5
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Re: LPG outboard on small 30 ft sailboat

Quote:
Originally Posted by Jammer View Post
That's backwards: it's actually 1.35 gallons propane = 1 gallon gasoline. In terms of locker space required it's about 2x because propane tanks are bulkier and can't be filled more than 80% full.
Yup, I stated that poorly. Thanks for the catch.

Shawn
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Old 18-07-2019, 11:00   #6
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Re: LPG outboard on small 30 ft sailboat

Boats that I volunteer on are equipped with Lehr LPG outboards. The consensus of all the volunteers is that these are the biggest downside of working with the organization. They are really hard to start, may not start at all. The comparison with our Yamaha 2-stroke is really striking.
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Old 18-07-2019, 12:08   #7
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Re: LPG outboard on small 30 ft sailboat

In 1985 my gas/propane motorhome had 2 gigantic cylindrical propane tanks mounted under it to go any distance. Perhaps 6 feet long each.
Ploy at the time to not pay DOT sales tax. Some USA vendors would refuse to fill them. The dual-fuel conversion was way less than sales tax.
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Old 18-07-2019, 12:15   #8
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Re: LPG outboard on small 30 ft sailboat

The couple of propane outboards I've seen seem really hard to start
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Old 18-07-2019, 12:24   #9
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Re: LPG outboard on small 30 ft sailboat

The LPG outboard (Lehr 2.5 HP) I use on my dinghy is incredibly reliable, much more so than any gasoline outboard I have ever owned. For a larger motor to propel a 30’ sailboat, I would recommend an aluminum propane tank that can be stored upright on deck. From this you can either run a gas hose directly to the motor (they came free with Lehr outboards, or you can buy one for $60), or buy a few refillable 1 Lb. cans ($15) from Flame King and their refill kit ($25). I do the latter, as I also use the cans for a Buddy Heater and the grill.
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Old 18-07-2019, 12:55   #10
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Re: LPG outboard on small 30 ft sailboat

I have been through three of them for use on a Precision 18.5.

Here are my pros and cons:

Pro's....they normally start very easily, even when used irregularly.

Cons's...

1. When they don't start it is usually because of a build-up of gas pressure in the cylinders...and if you whale on it long enough you can wreck the motor.

2. The so-called Lehr dealers in my area (Sarasota/Bradenton) will not touch a Lehr with a ten-foot pole.

3. West Marine does not want to touch with a faulty motor, even under the extended warrantee they sell.

4. Returning a motor directly to Lehr is a painful task. Took me a year to get them to take the first one back....then they send me one that did not work...then they send me one that I have not as yet used because I found an old 5 HP two stroke.

5. If you use the small camping tanks you will end up in a bouncy seaway with no skin on your knuckles when you try and change the tank as the hose it so recessed.

6. If you use a BBQ tank you practically sink you boat.
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Old 18-07-2019, 13:05   #11
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Re: LPG outboard on small 30 ft sailboat

Getting support from Lehr has gotten harder than the last post described, because they went out of business.
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Old 18-07-2019, 13:15   #12
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Re: LPG outboard on small 30 ft sailboat

I chartered a boat once that came with a dinghy with a 2.5 Lehr propane outboard. I thought it was great. It started on the first or second pull and ran clean without any odor. I can't speak to maintenance or long term reliability.
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Old 18-07-2019, 17:27   #13
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Re: LPG outboard on small 30 ft sailboat

I used a 5 hp Lehr outboard and found it incredibly unreliable.
After only a few hours of use, I discovered a propane leak in the maze of tubes under the cowl. I was fortunate to not have a fire. Since I was in a foreign country, there was no hope of warrantee work. A local marine mechanic finally fixed the outboard a month after I bought a new, gasoline outboard to replace it. I have not used the Lehr since it was repaired. Someone said Lehr KNEW the system was faulty but Lehr never offered a repair or buy-back.
I don't like gasoline on my boat. But gasoline is better than leaky propane.
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Old 18-07-2019, 19:25   #14
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Re: LPG outboard on small 30 ft sailboat

I can't wait for my Lehr 2.5 to die so that I can replace it with a Torqueedo electric for my 16' row/sailer.
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Old 20-07-2019, 13:00   #15
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Re: LPG outboard on small 30 ft sailboat

Quote:

As with electric alternatives, this works out just fine for motoring in and out of the harbor but tends to fall down when you decide to motor up the river all day since there's no wind.

I think that my point...

So maybe a still old style 1 cyl diesel (outboard cinese?) so recharging batteery and maybe hot water also....

With electric unless coupled with a 5kw genset for longer motoring ( heavy, bulky, low efficient conversions, ecc) and battery just to in and out from the mooring and short motoring...
The electric solution couple with many solar panels/windgen, ecc...

Am i correct?

thanks all for the answer
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