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This is my first post to this site. I've been lurking for awhile soaking up all the great info on here!

I see its been about 6 months since the last post regarding propane outboards. I'm looking to buy a 5 to 6hp motor for a 15ft Williwaw, 20" shaft I think. I'm curious if the propane powered motors are still working out well for those who have them. Are there any starting issues with them in cooler weather, say 60 F or so?
 

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This is my first post to this site. I've been lurking for awhile soaking up all the great info on here!

I see its been about 6 months since the last post regarding propane outboards. I'm looking to buy a 5 to 6hp motor for a 15ft Williwaw, 20" shaft I think. I'm curious if the propane powered motors are still working out well for those who have them. Are there any starting issues with them in cooler weather, say 60 F or so?

I have a Tohatsu 25 inch shaft propane outboard that I've used on my Avon Pro, a 16 foot Hyside cat, and my 18 foot Briggs Dory, all in all it's got about 20 hours on it and I have nothing but praise. No gas smell, quieter than a 2 stroke, and a little quieter than a Honda 5 HP, couple of pulls to fire it initially, then starts on the first pull after that. Did have an issue firing it on it's first run, took about 3 minutes of pulling to start it, but since then it fires right up. They aren't cheap like the Lehr, so you DO get what you pay for. Highly recommend the Tohatsu !!
 

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Yep, that they are, and while I haven't seen one up close and personal, it looks a LOT like a Tohatsu painted black with Mercury decals. Interesting that they only come in 15 or 20 inch shafts, the Tohatsu 25 inch shaft was a big selling point for me, cause you can always get the prop out of the water if it's too deep, but with a short shaft motor on a raft, I've had to move people to the rear of the boat to keep the prop in the water far enough so it doesn't cavitate..
 

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The Tohatsus look nice. I'm also aware that Mercury is coming out with some propane models.
The Mercury is a Tohatsu with different paint. Tohatsu makes all Mercury outboards less than 25 or 40 Hp.
 

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These look like really nice options - especially if you have $1800 lying around. There is a cheaper option if you have an old gasoline engine. There are kits available for around $200 to retrofit either two stroke or four stroke engines to run on propane. I did this for a client in the Philippines who owned a pearl farm - a crew of four did 90 outboard in three weeks so not that hard. The 2 stroke engines use a small oil injection pump. The four stroke burn pure propane. If I remember the kits came from India but sure you can find them on-line.
 

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Discussion Starter #13
Great replies everyone; I appreciate the info very much. I really like the idea of avoiding gasoline and fumes on a raft. My only remaining concern with propane is difficulty starting in cooler weather, but gas can have starting issues too. Like 2-years ago with a friends brand new Yamaha on the lower end of HC. Was 2-hours before we gave up and started rowing; just in time for the upstream winds to get started, of course:mad: It was about 75 degrees then so temperature wasn't a factor.
 

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I've never used a propane outboard...but its a very popular upgrade for Toyota rock crawlers and is dead simple and very reliable for that application. As long as propane flows into the engine and there is spark...it will run...even if the rig is tipped over on its side nearly upside down or even under water. It also runs super clean...oil lasts WAY longer with propane. They use LPG though...so maybe its different with a BBQ tank.

I think it would be great if someone made an upgrade kit just for the 4-6hp range of outboards. So far...I haven't really seen anything and I've definitely spent time searching. Maybe I'm not using the right words or something.
 

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Great replies everyone; I appreciate the info very much. I really like the idea of avoiding gasoline and fumes on a raft. My only remaining concern with propane is difficulty starting in cooler weather, but gas can have starting issues too. Like 2-years ago with a friends brand new Yamaha on the lower end of HC. Was 2-hours before we gave up and started rowing; just in time for the upstream winds to get started, of course:mad: It was about 75 degrees then so temperature wasn't a factor.

Well, it's been my life experience that motors, any internal combustion motor, is going to give you trouble at some point. I loaned a 2 stroke to some friends doing an Oct Deso, they came back cursing it, said they pulled on it for hours and it didn't start. I asked them to show me how they tried to start it, and they demonstrated. The only thing they neglected to do was to throw the ignition switch to on, 2 pulls and it fired. Something I have kept in the back of my mind ever since when faced with a situation like that.

The Tohatsu has never given me that grief, but then it is relatively new, that being said, judging on the overall construction and obvious engineering, it doesn't look like it would be prone to breaking down in normal use on a river.
 

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They use LPG though...so maybe its different with a BBQ tank.

Let’s take a look at LPG and what it is. Liquefied petroleum gas (LPG) is a term widely used to describe a family of light hydrocarbon gases. The two most well known gases in this family are propane and butane.
Both of these gases have similar qualities, this means people often get confused between the two. The gases can both be used as a fuel in heating, cooking, hot water, vehicles, refrigerants and much more.
Propane, which comes from natural gas processing and oil refining, is a flammable hydrocarbon gas that is liquefied through pressurization. It is commonly used for heating and cooking, but can be used for a wide range of residential and commercial uses


Meanwhile, butane is also a flammable hydrocarbon gas that comes from natural gas processing and oil refining. Butane on the other hand, is more commonly used as a propellant and refrigerant.

When comparing propane and butane, the most important differences come down to the boiling point of the gases. Propane has a boiling temperature of -42°C, whilst butane has a higher boiling point at -2°C.
This means that propane will continue to vaporize and turn to gas in colder climates, which is perfect for the cold winters we get here in Colorado and for outdoor use. When stored as a liquid in a tank, propane also exerts a greater pressure than butane at the same temperature. This makes it more suitable for exterior storage and use.
So, at the end of the day, LPG is Propane, the same stuff in the BBQ tank runs forklifts, rock crawler conversions and LPG powered motors and cars.


And yes, for those that find the need to point this out, I plagiarized and edited much of the above from the internet.
 

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Let’s take a look at LPG and what it is. Liquefied petroleum gas (LPG) is a term widely used to describe a family of light hydrocarbon gases. The two most well known gases in this family are propane and butane.
Both of these gases have similar qualities, this means people often get confused between the two. The gases can both be used as a fuel in heating, cooking, hot water, vehicles, refrigerants and much more.
Propane, which comes from natural gas processing and oil refining, is a flammable hydrocarbon gas that is liquefied through pressurization. It is commonly used for heating and cooking, but can be used for a wide range of residential and commercial uses


Meanwhile, butane is also a flammable hydrocarbon gas that comes from natural gas processing and oil refining. Butane on the other hand, is more commonly used as a propellant and refrigerant.

When comparing propane and butane, the most important differences come down to the boiling point of the gases. Propane has a boiling temperature of -42°C, whilst butane has a higher boiling point at -2°C.
This means that propane will continue to vaporize and turn to gas in colder climates, which is perfect for the cold winters we get here in Colorado and for outdoor use. When stored as a liquid in a tank, propane also exerts a greater pressure than butane at the same temperature. This makes it more suitable for exterior storage and use.
So, at the end of the day, LPG is Propane, the same stuff in the BBQ tank runs forklifts, rock crawler conversions and LPG powered motors and cars.


And yes, for those that find the need to point this out, I plagiarized and edited much of the above from the internet.
Yes...but the main difference between a Forklift tank and a BBQ tank is that the forklift draws liquid propane into an injector which then expands into a gas as it enters the engine manifold and BBQ use the vapors above the liquid in the tank... so not sure how much a difference that would make as far as how these run.

They are both propane...but used differently.
 

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Yes...but the main difference between a Forklift tank and a BBQ tank is that the forklift draws liquid propane into an injector which then expands into a gas as it enters the engine manifold and BBQ use the vapors above the liquid in the tank... so not sure how much a difference that would make as far as how these run.

They are both propane...but used differently.

Correct, and LPG is propane :) Which was my point. Larger engines need more propane to function and generate Horsepower, hence the liquid feed, whereas a smaller engine such as the Tohatsu doesn't need that much propane, and can and does run off a BBQ bottle with vapor. Not trying to be a smart ass here, but I thought the initial thing I was addressing was, is LPG different from Propane.
 

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Regarding running the propane outboard in cold weather. I ran Cat last December during a cold snap. We had two mornings below 20 degrees and it started and ran with no issues. The lower half of the tank would ice up after a few hours of running. I had painted the tank exterior dark blue and tried to keep some sun on it to prevent any internal vaporization issues. It worked.
 

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Correct, and LPG is propane :) Which was my point. Larger engines need more propane to function and generate Horsepower, hence the liquid feed, whereas a smaller engine such as the Tohatsu doesn't need that much propane, and can and does run off a BBQ bottle with vapor. Not trying to be a smart ass here, but I thought the initial thing I was addressing was, is LPG different from Propane.
I could see how you could read it that way... but my intention was only to say that my experience has been with automotive liquid propane injection systems and that they are very reliable, run super clean and will run in extreme conditions and that, not having experience with a system that uses a BBQ tank vapor based system, might be different. Sorry for the confusion.
 
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