Propane Outboards

Size matters.

With propane in a tank that is not an easy fill the smaller OB will be the best conversion

10hp costs a Gal of gas , even with a modern propane setup that might come close that is a bunch of fuel for a large engine.

A yachtty's 4 or 6 hp run at modest rpm will go thru a 20lb (4.2 gal) cylinder nice and slowly.

A 50 might empty it in a single hour.

One huge advantage of propane is the fuel is so clean that the gas engines (at least in noisemakers) get diesel service hours before needing replacement/rebuild.

Due to the lubrication issue , I would think a 4 stroke would be required.

FF,
Why would oil injection not get the job done? And how would propane adversely effect the 2stroke engine?
Seems to me ther'e must be a reason they don't do it. Must have todo w emission problems.

two strokes have only 105 to 125 LBS of compression, may that why they wont burn it??????? its somthing to think about,4 strke has a lot more compression

Oil injection would be fine , but on a 4 hp engine?

In theory it would be possible to use the high octaine rating of propane , with a higher compression ratio , but then it would ONLY be a propane engine.

Propane emissions are fine , that's why fork lifts and floor buffers work so well in occupied buildings.

Good thoughts all. I've seen oil injection on very small motorcycles. Hadn't thought of the lower compression though. Rick B should be able to clear the air on that one.
I think all the little propane OBs will run on the camp stove canisters. So running out w a small engine should'nt be a problem.
Perhaps we'll see propane 2 stroke OBs soon?

Over the weekend I got to play with one of the Lehr 5hp Propane Outboards. I took it out of the box, put a pint of oil in it, screwed a canister of gas in and two pulls later it was running. One pull starts the rest of the day. They should have a 9.5 out by the end of the year.
I'm going to get one of the 2.5HP motors for my canoe and Avon.

I should tell you that I have a financial interest in these motors as I am now a stocking dealer.

That said I'll now tell you the bad things.

The owners manual wasn't in the box but I was able to down load it off Lehr's website. The motor did come with a set of tools and a spare spark plug.

The cover latches were a little fiddly to get back on. The cover has to be aligned just right.

The steering tension screw was a little stiff.

One big advantage to propane is when the engine is not in use the gas will evaporate from the carb.

No deposits of varnish to clear after sitting a year.

This , and diesel life , is probably why it is used for so many RV's and in dirt house emergency systems that may not be run for a year or more.

Its a great fuel, tho more costly per hour than gas or diesel.

The TOTAL cost over the years in hassle and money may be far lower than gas or diesel.

IF you need 24/7 go diesel, otherwise propane might make sense.

When my 27 year old two-stroke 2.5 HP Mariner finally goes to that marina in the sky, I'll think about Lehr. The propane part is alright but the increase in weight could be an issue.

I worked in the Lehr Outboard booth at the Ft. Lauderdale Boat Show today. I must have started one twenty five or thirty times. It started on the first pull every time but three. Two of those times I forgot to crack the throttle and the third was just a weak pull.

They were showing the 9.9 hp motor for the first time but I didn't get to run it. The people there who had run it said it was very quiet.

I got to talk to the owner of the company about the efficency of the motors. He said that because propane mixes so well with the air and the fact that propane has a higher octtane than gasoline you get a much more complete burn of the fuel compared to small carburator gasoline motors.

HopCar said:

........... I got to talk to the owner of the company about the efficency of the motors. He said that because propane mixes so well with the air and the fact that propane has a higher octtane than gasoline you get a much more complete burn of the fuel compared to small carburator gasoline motors.

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You expected him to say something bad about his product?

Propane may turn out to be a great fuel for boats. I just worry about being on the leading (bleeding) edge. Since I bought a new 2 HP outboard this year, I am probably good for many years before I have to buy another one.

HopCar said:

He said that because propane mixes so well with the air and the fact that propane has a higher octtane than gasoline you get a much more complete burn of the fuel compared to small carburator gasoline motors.

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It burns cleanly but octane has nothing has nothing to do with that. Octane is a measure of knock resistance, nothing more, nothing less.

Rick, you're correct, the higher octane of propane doesn't get you any more power unless you increase the compression ratio to take advantage of it. These engines have compression ratios calculated to take advantage of the higher octane of propane.

Any idea how they start in c-c-c-cold weather? I might be interested in the 9.9 as an emergency kicker...which brings up another question, will there be a high thrust model?

A propane engine will burn a bit more fuel than a gas engine.

You will not notice a difference in sound.

There will probably be a slight propane smell.

Most propane engines run perfect all the time and no choke will be necessary.

Propane is very cheap right now compared to gasoline and I'm considering converting my old Buick but the cost of fuel for a small OB is fly stuff.

The safety issue in a boat is dependent mostly on the chances of it leaking into the boat and how much of it would be a real hazard. The probability of fuel line connectors leaking should be investigated.

Right now the availability of the two fuels is the probably the only significant difference between the propane OB and the gas OB. And for that reason I'd choose gas at this time.

My preliminary mind's eye picture is of a fibreglass tank (or two?) mounted on the corner(s) of the swim grid. Zero leakage hazard.

Our area is sparsely populated and marinas are about 50 miles apart so a dependable kicker is something to seriously consider, especially if you want to go poking around in the more remote nooks and crannies.

Dependable cold weather starts are a must.

Murray, I don't know about cold weather starting, the ones I've played with were all in Florida. I started a 2.5 hp Lehr about thirty times yesterday. It started on the first pull all but once. The weather was clear and cool in the low seventies. (note to Chamber of Commerce, don't forget to send the check).

Low temperature starts is certainly a concern. I'll see what I can find out.

I haven't heard any talk of a high thrust version, but I'll ask. I think that's a great idea. Some kicker motors don't get used often and the carbs can gum up between uses. Not a problem with propane. What horse power would you be interested in?

HopCar: How do the outboards run on a propane/butane blend? Outside the US, so called "propane" can have more butane than propane percentage wise in the blend. The warmer the country the higher the butane concentration. I know the higher blends don't burn as hot when grilling or using the stove/oven so I'm curious about the blends and their effect on the propane outboards performance.

MurrayM said:

Dependable cold weather starts are a must.

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Starts probably won't be much of a problem. Keeping it running and producing useful power might be.

http://www.documentation.emersonprocess.com/groups/public/documents/bulletins/d4500147t012.pdf

Re the cold start concern I worked where we had 5 or 6 small trucks running on propane in western Washington State and never experienced any starting problems. I also had my family car running on propane and no troubles either. In Minnesota in January ther'e could be issues but who'd be boating then and there.

But I wouldn't buy a small propane OB. Just not enough advantages. But a 75hp two stroke OB I'd consider w it's much lower weight.

MurrayM said:

My preliminary mind's eye picture is of a fibreglass tank (or two?) mounted on the corner(s) of the swim grid. Zero leakage hazard.

Our area is sparsely populated and marinas are about 50 miles apart so a dependable kicker is something to seriously consider, especially if you want to go poking around in the more remote nooks and crannies.

Dependable cold weather starts are a must.

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If you're thinking of storing propane on a boat, you might want to consider a ready made propane locker or at the very least, copy the construction and safety features of a commercial propane locker.

Manyboats, if they made a small 2 cycle engine sized for your dinghy would you be interested in propane?

What would you use a 75 HP 2 cycle for?

HopCar,
75hpOB? ... I'd replace my 60hp ridiculously heavy 4 stroke for a much lighter engine that burns $2 a gallon fuel. The propane OB would be stone age simple compared to the very advanced fuel injected 4 stroke. It's so complicated it scares me but it runs extremely well ... no perfect .. and that counts for a lot but if I was shopping and a 2 stroke propane 3 or 4 cyl OB was available I 'd probably would buy one. I should admit here that no such thing exists and ther'e is probably a very good reason for that. I think we talked about 2 stroke propane OBs before.

Small 2 stroke propane OBs? What advantage would they have? The only thing I don't like about small (2 to 6hp) OBs is that they shake too much and would like to see multi-cylinder 2 stroke engines. I had a 3hp Evinrude. It was perfect except it had seen too much sea water and had cooling system issues. Would sure love to have a new one. The Evinrude weighed 34 lbs and had two cylinders. Four times as many power strokes per revolution as the 4 stroke singles.

HopCar said:

What horse power would you be interested in?

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I hear there is a 9.9 coming soon...that's the one I'd be interested in taking a look at.

"Small 2 stroke propane OBs? What advantage would they have?"
Same advantage big two strokes have over four strokes, weight.
I'm buying a 37 pound four stroke to replace a 22 pound 2 stroke.
That 15 pounds will make a difference to my back and my canoe.
I will get 1/2 horse power more and a neutral for the additional weight.
It will also start when I pull the string after sitting a few weeks.

I agree with you about multi cylinder vs single cylinder.

Murray, I saw the 9.9 Lehr at the show. They should be available in a month or two.

Wha? My 1981, five-horsepower, two-cycle, one-cylinder Seagull was smooooth.

RickB said:

Starts probably won't be much of a problem. Keeping it running and producing useful power might be.

http://www.documentation.emersonprocess.com/groups/public/documents/bulletins/d4500147t012.pdf

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Thanks for that,

Temperatures do go down to -20 Celsius, or -4 fahrenheit around here a couple times a winter, but at that point the channels are thick with fog and the anchorages begin to freeze due to the large amounts of fresh water flowing into them. Think I'll be staying home during the coldest cold snaps.

The lowest temperatures I'd be heading out in would be around minus 10 Celsius, or 14 degrees fahrenheit. The propane should still be "perky" at that temperature, shouldn't it, as long as the tank was full?

markpierce said:

Wha? My 1981, five-horsepower, two-cycle, one-cylinder Seagull was smooooth.

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Yeah, but that was just because it wouldn't start.

MurrayM said:

The lowest temperatures I'd be heading out in would be around minus 10 Celsius, or 14 degrees fahrenheit. The propane should still be "perky" at that temperature, shouldn't it, as long as the tank was full?

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Probably but who knows. The draw off rate is going to be small for a tiny outboard but with a cold and frosted tank the amount you can boil off goes down rapidly with temperature, just drawing it off lowers the temperature until no matter how full the tank is the pressure becomes too low to supply the engine.

Larger engines use a "vaporizer" to ensure a supply of gas at all flow rates. Again though, these things are so small it might not matter.

It wouldn't be too dificult to put the outboard and the propane tank into a home freezer for a few hours and then try to start it.

That is, if one really wanted to know. It would be a good question to ask of the manufacturer. I would think they would have already tested the motor at low temperatures.

A two cycle outboard is great in the case of a dinghy where you may have to lift the motor on and off the dinghy. The decrease in weight is significant.

Unfortunately, the USA's EPA doesn't care much about our silly little problems and has pretty much made them unavailable in the USA.