Gas to Electric Outboard for dinghy

[rwidman]

It seems a lot of people misunderstood the question. The OP was asking about replacing his outboard motor, not his dinghy.

I replaced a Honda 2HP 4 stroke with an ePropulsion Spirit 1 plus. It is much more reliable and I have never been sorry I did it.

[wingssail]

Originally Posted by Messing About

How often do you all hear about dinghy’s and or outboards being stolen from dinghy docks? As a future solo cruiser, I worry about this. Any prevention tips, would be appreciated.

Most dingy thefts occur while the dingy is tied astern of the mother ship at night. I've rarely heard of theft from dingy docks. We used to have a long bicycle lock and wire from the motor clamps, through the gas tank handle, through the dingy bow eye and chained to the dock. But we observed that none of the other dingys were locked. We stopped doing that.

However we see and hear of dingys being stolen every year, mostly from new cruisers who leave them tied astern of their yachts every night.

We lift the dingy and motor on a spin halyard every night (and often during the day). There have been cases where a thief will drive his Panga under someone's hanging dingy and simply cut the halyard with a machete, dropping the dingy right into his boat, and he drives away. My lifting bridle is plastic coated lifeline wire, not easy to cut with a whack of the machete. If I am worried about theft I also put a chain from the motor to a stanchion on the big boat. Final option is to lift the dinghy and motor right onto our foredeck which is also good if big winds are expected. A big primary winch that can be reached by the halyard tail makes this job very easy for us.

[Adelie]

Originally Posted by NPCampbell

Small dinghy electric outboards + battery are almost always heavier than a comparable gas outboard + gas.

31 lbs - Suzuki 2.5 HP with full tank
31 lbs - Honda 2.3 HP with full tank
38 lbs - Torqeedo 1103 (only 1.5 HP)

59 lbs - Tohatsu MFS6D 6HP with full tank
99 lbs - Torqeedo Cruise 3.0 (only 4HP) with Power 24-3500 battery
115 lbs - Navy 3.0 6HP (only 4HP) + smallest E40 batt

.....

The only one of the above outboards that can get a dinghy on a plane is the 6hp Tohatsu. And then only if the dinghy is an ultralight RIB or a Porta-Bote and with only one person aboard.

That means that all the others will have a top speed within a 1/2kt range, maybe 3/4kt.

So most of the above electric motors are overkill for a dinghy.

The trolling motor system I proposed in post #62 would be about as fast as all of the gas motors above except the 6hp.
https://www.cruisersforum.com/forums...ml#post3666841
Weight would be
The motor is about 20lb and a 50Ahr LFP battery is 12lb. 32lb total but in 2 packages that would be easier to load and unload than the lightest ICE outboard.
If you mount a 100W solar panel on the dinghy add another 15lb for the panel plus lets say 5lb for struts.

[Shaneesprit]

The batteries on Torqeedo and E-Propulsion are removable- I would just take them with you in a bag, although they are no so light.
A lot less likely to go missing if you have the battery

[Adelie]

Originally Posted by sailingharry

Indeed, you can have both an electric outboard and a gasoline outboard. That's over double the cost of just the gasoline, plus additional storage issues. And a gas outboard that isn't run often leads to carburetor problems.

On the mothership, a diesel generator sufficiently large to give you the propulsion you need is likely to cost even more than the diesel engine you could have put in. Plus the cost of the electric motor, batteries, controls, etc.

EP has tremendous appeal if it is a standalone system. Much less if you still need all the dino systems as well.

That depends on what you define as sufficient, your definition is not universal, nobody's is. Also you are mixing in questions about propelling the mothership as well as dinghy and they are very different uses, different needs and expectations.

Currently if I was outfitting a vessel (Cal 34 or 36 for preferrence) (with a dead inboard) I would:

Install a 10kW electric motor ($5k) and a 200Ahr/48v bank. ($1160) on the mothership
Buy a10hp high thrust outboard. ($3600)
Mount a bunch of solar on the mothership ($1k or so)
Install bracket on the mothership for the above. ($150)
Total so far about $12k or so.

Buy Riptide & 50Ahr LFP battery for dinghy as detailed previously ($750).
Mount 100W solar panel on dinghy as detailed previously. ($150)

What's a replacement inboard cost? $10k or so.

For day to day use on the mothership, EP getting in and out of harbor/marina/anchoring. If I was in a position to take my time, I could proceed at 2.3-2.5kt under solar alone for long distances.

If I had need to make 5.0-6.0kt for extended distances then I would fire up the 10hp.

I am a diehard sailor. If the wind is blowing I sail; or motorsail if I'm trying to meet a schedule which is a bad idea to begin with when cruising.

For day to day dinghy use I would use the trolling motor.
If I have need to go a significant distance without staying overnight or don't want to take the mothership, the 10hp goes on the dinghy and off I go.

A 10hp high thrust will get most dinghies on a plane with 2 folks and at least a moderate amount of load. Using a 10hp high trust will result in a top speed of 12-14kt instead of 16-18kt you would get using a 15hp outboard. And it will use less fuel per mile. I'm willing to sacrifice time for decreased fuel use. You may not, your choice.

I would also consider getting a Honda EU2200 generator, same fuel as the outboard. There's no need to get a diesel generator, no reason to store an extra type of fuel.


OK issues with carburators clogging after sitting a while can often be traced ethanol in the gas, at least in the US. Most or all stabilizers really don't do anything for this. How do you get ethanol out a gas?

By ADDING WATER. Preferably with food coloring in it at the rate of about 1/2gal water to 5gal fuel. Shake up the container, let it sit for a while then drain off the colored water which should now be about 1gal leaving you with about 4.5gal fuel. Ethanol is hydroscopic and would rather glom onto water molecules rather than hang out with gas molecules. Food coloring is to make it easy to tell when you've drained off all the water/ethanol mixture. Ethanol is a octane booster (2 points or so) so it's best to start with a higher octane gas or to add an octane booster. Make sure the octane booster is not just ethanol, some are.

[Adelie]

Originally Posted by Messing About

How often do you all hear about dinghy’s and or outboards being stolen from dinghy docks? As a future solo cruiser, I worry about this. Any prevention tips, would be appreciated.

My sense from a lot a cruisers' anecdotes is that most thefts are after the motor. If you use an electric motor to get ashore, you are at less risk of theft.
A smaller ICE outboard is also a low probability target, my sense is that thieves get interested at about 15hp but may go as low as 9.9hp.

Cable and padlock to secure the motor to the dinghy and to the mothership when at anchor and maybe to a dock when ashore. On the beach, probably nothing good to lock up to.

I heard that defacing the motor cover to make it unique and easy to identify also helps.

[wingssail]

Originally Posted by Adelie

The only one of the above outboards that can get a dinghy on a plane is the 6hp Tohatsu. And then only if the dinghy is an ultralight RIB or a Porta-Bote and with only one person aboard.

That means that all the others will have a top speed within a 1/2kt range, maybe 3/4kt.

So most of the above electric motors are overkill for a dinghy.

The trolling motor system I proposed in post #62 would be about as fast as all of the gas motors above except the 6hp.
https://www.cruisersforum.com/forums...ml#post3666841
Weight would be
The motor is about 20lb and a 50Ahr LFP battery is 12lb. 32lb total but in 2 packages that would be easier to load and unload than the lightest ICE outboard.
If you mount a 100W solar panel on the dinghy add another 15lb for the panel plus lets say 5lb for struts.

Well, Adelie, You're going to have a motor, battery, and solar panel (and struts) on the dingy? Sort of makes me think of a mini-African Queen.

Where do you put that dingy? Do you unload it every day, put it up on Davits? or leave it floating in the water waiting for the next wind gust to catch the solar panel and sail it off like Ben Franklin's kite?

But I think you are wrong about the capability of the outboards. I used to have a 11ft Avon (inflatable floor) and we had a 4hp Mercury which would easily plane with one person and go very nicely with two persons, but not planing, of course. The gas tank was on top but I had an external tank for longer voyages. That motor could be held up in one hand. Easy.

We also had a 25hp Merc which made that boat fly (his' and her's motors). We sold them both to buy our current 67lb 15 hp Mercury. It lifts off in an instant with a spin Halyard. On our newer Big Zodiac it is light, fast, easy to handle, safe and capable of long distances.

And I think you are being optimistic about the performance you will get from either your electric outboard's ability to speed any dingy at anything over about a knot and a half, (it is only .84 HP) and the solar panel.

Finally the 100 watt solar panel will need a full day's direct sunlight to give you one hour's worth of electric motoring, assuming zero loses in the battery.

So this may work for you if you are determined to go electric, but you will give up a heap of capability and flexibility when you kiss off the ICE.

[rslifkin]

I've got the above mentioned 6hp Tohatsu on our dinghy (12 foot aluminum skiff). Adelie's thought that it'll only plane the lightest of dinghies and only with 1 person is a bit off in my opinion. It's not a rocketship, but with just me (plus an anchor, oars, and full 3 gallon tank of gas) on board it'll do almost 14 kts. With 2 of us the best I've seen so far was a little over 9 kts (and just barely on a clean plane), but I'm still experimenting with the trim tabs on the dinghy as well as prop selection for the outboard. I'm pretty confident that I should be able to get 10 kts out of it with 2 of us and it'll still plane with 2 + dog.

The closest equivalent performance electric setup I've found is the ePropulsion Navy 6.0. With the appropriate battery, it would weigh about 250 lbs (way too heavy to lift in davits and would eat into dinghy payload severely). Based on its power output and ePropulsion's test data, it would run just slightly slower than the 6hp Tohatsu (due to the extra weight, as a 6kw electric is about 8hp, not the 9.9 equivalent they claim). But the Tohatsu with a 3 gallon tank of fuel is only about 80 lbs total, so there's a big difference there. Even going up to an 8hp gas outboard you'd only be adding another 25 lbs over the 6hp.


If I were content with non-planing speeds, we'd be comparing something like the 29 lb Suzuki 2.5hp (plus a bit if carrying extra fuel to refill the internal tank). The small electric options are closer to 40 lbs, but that's still pretty light. And given a dinghy like mine, while they'd likely be a little slower than the 2.5 hp gas engine, the ePropulsion Spirit 1.0 or a Torqeedo should have no problem pushing it to 4 kts or so. 1kw is about 1.3hp (not the 3hp equivalent the manufacturers claim). It may have equivalent low speed thrust to a 3hp gas outboard, but as far as top speed capability, it's not a 3hp.


For the non-planing scenario (assuming you don't need to go long distances where speed matters and you have a dinghy that performs acceptably at low speeds), I'd be 100% for the electric option (provided you have a way to charge it). It's just the planing dinghy scenario where it's not quite a fit yet.

[Shaneesprit]

Originally Posted by sailingharry

Indeed, you can have both an electric outboard and a gasoline outboard. That's over double the cost of just the gasoline, plus additional storage issues. And a gas outboard that isn't run often leads to carburetor problems.

On the mothership, a diesel generator sufficiently large to give you the propulsion you need is likely to cost even more than the diesel engine you could have put in. Plus the cost of the electric motor, batteries, controls, etc.

EP has tremendous appeal if it is a standalone system. Much less if you still need all the dino systems as well.

On a mothership putting EP is jumping the gun and putting valuable resources to poor use. Might as well wait for the Technology to catch up. Torqeedo will soon be producing Battery-Hydrogen-Hybrids of 50kW so in 10 years or so should be able to get a real propulsion system.

[sailingharry]

Originally Posted by Adelie

Currently if I was outfitting a vessel (Cal 34 or 36 for preferrence) (with a dead inboard) I would:



Install a 10kW electric motor ($5k) and a 200Ahr/48v bank. ($1160) on the mothership

In diesel engines, excess hp hurts fuel economy at low rpm. A 25 horsepower engine being used at 12 horsepower is much less efficient than a 12 horsepower engine being used at 12 horsepower. But this does not apply to electric motors, where there is almost no penalty for oversizing them.

Day to day, my most aggressive use of my available diesel horsepower is in maneuvering. Full throttle for 3 seconds and then back to zero with the rudder hard over can really make the boat spin. Or in stronger winds, come into the dock at 2 or 3 knots, and then call up full reverse to kill the boat speed in a mere 10 or 15 ft (super nice if you can manage it port side to). Or making the entrance in Cape Porpoise (Kennebunkport) with the seas breaking on the rocks on both sides of a narrow channel where full throttle gives you maneuvering and gets you through the 300 yards quickly. There are those days, like going into the Montreal Harbor in 6-7 knots of current where I need every horsepower for an extended duration, (it's 3/4 mile up river -- do the math) but day to day my biggest horsepower demands are in short bursts that have relatively little impact on Ah consumption.

Given the above two paragraphs, I would double that motor from 10 kW to 20 kw (or even 25). That gets the electric motor closer to the original diesel that that boat came with (it probably had 35 hp, at least 30). Might add a thousand or two to the total cost, but it'll give you the short burst power that is so critical.

[Rhonda S]

We're going with two electric motors. One lightweight and a bigger one for diving. If anyone is interested here is our dingy comparison and toward the bottom all the electric motors we considered. Gear: Tender We have the smaller engine and will be receiving the larger engine and dingy in the next month or so. Then its off to Newport Beach for sea tests!

[newhaul]

Originally Posted by sailingharry

In diesel engines, excess hp hurts fuel economy at low rpm. A 25 horsepower engine being used at 12 horsepower is much less efficient than a 12 horsepower engine being used at 12 horsepower. But this does not apply to electric motors, where there is almost no penalty for oversizing them.

Day to day, my most aggressive use of my available diesel horsepower is in maneuvering. Full throttle for 3 seconds and then back to zero with the rudder hard over can really make the boat spin. Or in stronger winds, come into the dock at 2 or 3 knots, and then call up full reverse to kill the boat speed in a mere 10 or 15 ft (super nice if you can manage it port side to). Or making the entrance in Cape Porpoise (Kennebunkport) with the seas breaking on the rocks on both sides of a narrow channel where full throttle gives you maneuvering and gets you through the 300 yards quickly. There are those days, like going into the Montreal Harbor in 6-7 knots of current where I need every horsepower for an extended duration, (it's 3/4 mile up river -- do the math) but day to day my biggest horsepower demands are in short bursts that have relatively little impact on Ah consumption.

Given the above two paragraphs, I would double that motor from 10 kW to 20 kw (or even 25). That gets the electric motor closer to the original diesel that that boat came with (it probably had 35 hp, at least 30). Might add a thousand or two to the total cost, but it'll give you the short burst power that is so critical.

The overall cost is not acceptable to me . I paid 100 for my westerbeke 10-2 that is going into my 29 columbia defender the additional funds would pay for the rest of my life's cruising fuel use . And at least several years cruising costs for me .
Now I do have a min Kota 65mx electric trolling motor and a 100ah briefcase lifepo4 battery to run it . Gas engine as well . Options are what we all should be looking at

[Shaneesprit]

Originally Posted by newhaul

The overall cost is not acceptable to me . I paid 100 for my westerbeke 10-2 that is going into my 29 columbia defender the additional funds would pay for the rest of my life's cruising fuel use . And at least several years cruising costs for me .
Now I do have a min Kota 65mx electric trolling motor and a 100ah briefcase lifepo4 battery to run it . Gas engine as well . Options are what we all should be looking at

I would trial the trolling type outboard before buying - I was in one at the weekend, after waiting for an hour for it, I could row in 40 mins.
I am looking at the alternative EP outboards and think I could manage a 1kW unit on the dingy

[newhaul]

Originally Posted by Shaneesprit

I would trial the trolling type outboard before buying - I was in one at the weekend, after waiting for an hour for it, I could row in 40 mins.
I am looking at the alternative EP outboards and think I could manage a 1kW unit on the dingy

No not purchasing I have owned it for a long while . Used to use it on my scanoe trolling for trout.

[silvercreek]

You could also consider gluing an Apple AirTag inside the outboard casing. In the unlikely event it does "disappear," it would let you geo-locate it for recovery.