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Thinking of using a Mercury 5hp Propane Outboard - Any Advice?

May 25, 2019
23
Catalina Capri 18 Bronx, NY
This is for small boat owners, I would be using it on my Catalina 18, but thought I would post here to see if I could get advice from a larger group.
I need a new outboard. Only use it in warmer months in Long Island Sound, and would like to avoid the smell and mess of gasoline.
We use the motor for maybe 20 minutes max each day sail.
I would like to use only 1lb camping cannisters, and I have a plan to store them safely inside of PVC pipe with holes for leaks, hanging from the rails. Not enclosed in anything that would trap the propane.
Some people in other forums have warned me away from trouble with propane motors, but nothing specific.
Any advice here would be appreciated.
 
Oct 22, 2014
15,791
CAL 35 Cruiser moored EVERETT WA
Why not. You might even be able to use an electrical trolling motor doing away with all the smells- gasoline and propane. Charge the battery with solar. Sail the boat using the solar powered wind.

You have options.
 
Jan 11, 2014
7,718
Sabre 362 113 Fair Haven, NY
The technology has been around for long enough to work out the kinks, propane does have some advantages. You might think about buying a small refillable tank, it may be more cost effective over the long haul and keeps those little bottles out of the land fill.

Propane isn't really the issue with your motor choice. The 5 hp motors weigh about 60 lbs, that is a lot of weight to hang on the transom of a 18' boat. Can the the motor mount and transom support the weight? A 2 or 3 hp motor would drive the boat fast enough.

Have you thought about going electric? Torqeedo makes a nice outboard, considerably lighter and no fuel issues.
 
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May 25, 2019
23
Catalina Capri 18 Bronx, NY
Thank you. I am aware of just the Torqueedo motors that are strong enough to push my boat on the sound. And these are about double the price of a standard gas or propane engine, so not an option. Thanks!
 
May 25, 2019
23
Catalina Capri 18 Bronx, NY
Thanks Dave,

As I replied to John, the Torqueedo's are just out of my budget range.

The engine weighs pretty much the same as the Yamaha 4HP that died on us, so I think I am good for weight.

I will consider a smaller, maybe 11lb tank for use, but living in New York City, I will have to research the options for where i could get that refilled, and then i would need to have 1lb tanks for backup. I do have the same concern about the waste factor on the small bottles.

Good to hear that you think the Propane tech is mature enough to count on.

The technology has been around for long enough to work out the kinks, propane does have some advantages. You might think about buying a small refillable tank, it may be more cost effective over the long haul and keeps those little bottles out of the land fill.

Propane isn't really the issue with your motor choice. The 5 hp motors weigh about 60 lbs, that is a lot of weight to hang on the transom of a 18' boat. Can the the motor mount and transom support the weight? A 2 or 3 hp motor would drive the boat fast enough.

Have you thought about going electric? Torqeedo makes a nice outboard, considerably lighter and no fuel issues.

 
May 25, 2019
23
Catalina Capri 18 Bronx, NY
Should have also mentioned that the Cat 18 has a lead keel, making the weight of the motor a non-issue.

Propane isn't really the issue with your motor choice. The 5 hp motors weigh about 60 lbs, that is a lot of weight to hang on the transom of a 18' boat. Can the the motor mount and transom support the weight? A 2 or 3 hp motor would drive the boat fast enough.
 
Mar 20, 2004
1,657
Hunter 356 and 216 Portland, ME
We've got a Lehr 2.5 and a Tohatsu 5p propane, and after years of fighting gasoline and ethanol I'll never go back. I looked at the merc, and thought the tohatsu was better built and engineered. It's made in Japan, I'm pretty sure the merc is built in China.
The tohatsu is on our Hunter 216, 1600 lbs including a 500lb keel so probably similar to your boat; it drives her really well. I use a Coleman dual 1lb bottle manifold/holder (about $35 on amazon) and it works well - 2 bottles in parallel with good valving. I think a 1lb bottle doesn't have enough flow to run a 5hp at higher throttle settings, and if you try as it empties it gets really cold and flows even less. no such problems with the 2.5
 
Jan 11, 2014
7,718
Sabre 362 113 Fair Haven, NY
We've got a Lehr 2.5 and a Tohatsu 5p propane, and after years of fighting gasoline and ethanol I'll never go back. I looked at the merc, and thought the tohatsu was better built and engineered. It's made in Japan, I'm pretty sure the merc is built in China.
The tohatsu is on our Hunter 216, 1600 lbs including a 500lb keel so probably similar to your boat; it drives her really well. I use a Coleman dual 1lb bottle manifold/holder (about $35 on amazon) and it works well - 2 bottles in parallel with good valving. I think a 1lb bottle doesn't have enough flow to run a 5hp at higher throttle settings, and if you try as it empties it gets really cold and flows even less. no such problems with the 2.5
Most, if not all, low HP Mercs are rebranded Tohatsus.
 
Jan 19, 2010
9,950
Hunter 26 Charleston
Why not. You might even be able to use an electrical trolling motor doing away with all the smells- gasoline and propane. Charge the battery with solar. Sail the boat using the solar powered wind.

You have options.
I had a boat rigged like that in the past. Worked very well. Leave the solar plugged in and you are at full charge each time you come back to the boat.
 
May 25, 2019
23
Catalina Capri 18 Bronx, NY
Chuck,

Can you send me a link to the combiner and hose you are using. I have been unable to find a safe way to adapt from the 1lbs to the engine, just brass adapters that look like they will freeze my fingers off when disconnecting and no shut-off mechanism.

Any details you can provide would be welcome.


We've got a Lehr 2.5 and a Tohatsu 5p propane, and after years of fighting gasoline and ethanol I'll never go back. I looked at the merc, and thought the tohatsu was better built and engineered. It's made in Japan, I'm pretty sure the merc is built in China.
The tohatsu is on our Hunter 216, 1600 lbs including a 500lb keel so probably similar to your boat; it drives her really well. I use a Coleman dual 1lb bottle manifold/holder (about $35 on amazon) and it works well - 2 bottles in parallel with good valving. I think a 1lb bottle doesn't have enough flow to run a 5hp at higher throttle settings, and if you try as it empties it gets really cold and flows even less. no such problems with the 2.5
 
Mar 20, 2004
1,657
Hunter 356 and 216 Portland, ME
Most, if not all, low HP Mercs are rebranded Tohatsus.
That's what I thought, too, Dave. I asked a Merc dealer where it came from and he said it wasn't made by Tohatsu. Also was more expensive than the tohatsu!
 
Mar 20, 2004
1,657
Hunter 356 and 216 Portland, ME
Chuck,

Can you send me a link to the combiner and hose you are using. I have been unable to find a safe way to adapt from the 1lbs to the engine, just brass adapters that look like they will freeze my fingers off when disconnecting and no shut-off mechanism.

Any details you can provide would be welcome.
Walmart carries it - $67..
Coleman Gemini Power Pack, Model R9708-A30C
 
Jan 11, 2014
7,718
Sabre 362 113 Fair Haven, NY
That's what I thought, too, Dave. I asked a Merc dealer where it came from and he said it wasn't made by Tohatsu. Also was more expensive than the tohatsu!
He doesn't know what he is talking about. Take a look at the specs and images of the Merc and Tohatsu, everything is the same except for the cover and the color. The weight, bore and stroke, etc are the same.

Larger Merc may not be made by Tohatsu, the smaller ones are. The 5 hp is virtually identical to my 4hp Merc which is most definitely a Tohatsu. One give away is the shift lever


 
May 25, 2019
23
Catalina Capri 18 Bronx, NY
Thank you! I had been searching and would only come up with results for splitting the output of a 20lb tank into 2 appliances.
I think I am going to go with using an 11lb tank, since I found a local hardware store that will refill them, and having 2 onboard at all times will make it easier to not worry about running out of fuel or changing tanks mid sail, etc. Not to mention the environmental benefit of not using the regular 1lb cans that are not refillable.

Walmart carries it - $67..
Coleman Gemini Power Pack, Model R9708-A30C
 
Oct 22, 2014
15,791
CAL 35 Cruiser moored EVERETT WA
having 2 onboard at all times will make it easier to not worry about running out of fuel or changing tanks mid sail, etc. Not to mention the environmental benefit of not using the regular 1lb cans that are not refillable.
Appears to be a plan. Just be sure to have them properly stored in sealed, vented overboard locker or outside off the transom. You do not want that gas to leak inside the boat and pool in your bilge.

 
May 25, 2019
23
Catalina Capri 18 Bronx, NY
For sure, my plan is to keep them in milk crates that have tops, tied off to the side rail, with a safety line through the steel grip of the tank. Nothing stored in any solid enclosure at any time. Thanks for the help!
 
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