Dingy Motor

[Hippocampus]

Excellent post NE. Sums it up nicely. Interestingly think high fuel prices will drive move to more gas than battery driven dinghies. Believe folks will think it through and decide to go a bit bigger with dinghy selection allowing them to increase dinghy use while decreasing boat use. It surprised me that once we were full time cruising and wanted to go anywhere within a 5-7nm radius if the weather permitted we’d take the dinghy. Similarly for exploring. Even when picking up stores unless multiple trips were required. That was on a sailboat. So avoiding reanchoring was the main driver. Now on a trawler with a 40hp engine will add in fishing and major restocking including lots of heavy liquids. Suspect transient slip fees will be avoided whenever possible due to inflation again producing more dinghy use.

 

[kthoennes]

I think that's right on target (post 31). In a different thread about that recent boat theft and destructive joyride in Newport Harbor, I mentioned what it took to fire up our boat and pull out. I counted like 14 steps moving out of the slip, and then about 13 steps coming back in and tying up, to say nothing of the stress of coming back in a stiff cross-wind. In my mind the dinghy's lower fuel consumption is only part of it. Unless we're purposely going for a long or overnight run, might as well avoid the hassle and burning hundreds of dollars in gas.

 

[NEtrawler58]

I think that's right on target (post 31). In a different thread about that recent boat theft and destructive joyride in Newport Harbor, I mentioned what it took to fire up our boat and pull out. I counted like 14 steps moving out of the slip, and then about 13 steps coming back in and tying up, to say nothing of the stress of coming back in a stiff cross-wind. In my mind the dinghy's lower fuel consumption is only part of it. Unless we're purposely going for a long or overnight run, might as well avoid the hassle and burning hundreds of dollars in gas.

I don't disagree, but again seem more like comparing a bicycle and motorcycle, depends on what you intend to do. (or maybe better comparison is a compact car and an RV). If you're just going to go a couple miles down a river to tie up at a restaurant for lunch then return, a dinghy trip makes a lot of sense. But if I'm only going out for an afternoon, even if only a few miles to drop anchor and relax for a couple hours, I wouldn't want to do that in a dinghy. A dinghy can get you from A to B quickly and efficiently, but not really a place to hang out on.

 

[psneeld]

I don't disagree, but again seem more like comparing a bicycle and motorcycle, depends on what you intend to do. (or maybe better comparison is a compact car and an RV). If you're just going to go a couple miles down a river to tie up at a restaurant for lunch then return, a dinghy trip makes a lot of sense. But if I'm only going out for an afternoon, even if only a few miles to drop anchor and relax for a couple hours, I wouldn't want to do that in a dinghy. A dinghy can get you from A to B quickly and efficiently, but not really a place to hang out on.

Much like one's dingy speed/range needs, the size and type of dingy might determine how comfy a hangout it is.

I remember a couple great hours at anchor in my dingy with a friend listening to a waterfront concert. We had some of the best seats in the house. Just one of many fun afternoons in a standard style dingy

The big generalizations made in these opinion threads really leave things wide open for interpretation.

 

[FWT]

Believe folks will think it through and decide to go a bit bigger with dinghy selection allowing them to increase dinghy use while decreasing boat use.

50-50 would be my guess. Whenever I see a clip or comment about making a dingy change (apart from simply replacing an aged one) it seems split. Some go smaller and complain their dingy is too big, making storage harder and it more of a pain to launch and retrieve. Others want more, for the reasons you cite. The only conclusion I can draw is everyone's needs and preferences differ, and can differ over time causing a desire to make new choices.

 

[O C Diver]

Excellent post NE. Sums it up nicely. Interestingly think high fuel prices will drive move to more gas than battery driven dinghies. Believe folks will think it through and decide to go a bit bigger with dinghy selection allowing them to increase dinghy use while decreasing boat use. It surprised me that once we were full time cruising and wanted to go anywhere within a 5-7nm radius if the weather permitted we’d take the dinghy. Similarly for exploring. Even when picking up stores unless multiple trips were required. That was on a sailboat. So avoiding reanchoring was the main driver. Now on a trawler with a 40hp engine will add in fishing and major restocking including lots of heavy liquids. Suspect transient slip fees will be avoided whenever possible due to inflation again producing more dinghy use.

I can see the crowd that uses their dinghy as a high speed launch, surf boat or a small sport fishing boat staying with gasoline powered outboards, but the dinghy crowd, not so much. In my last 6 years of cruising, the switching to electric has been staggering. If you're into viewing bird and animal life, displacement speed silent electric is the answer. While I wouldn't expect most to buy electric if they have a perfectly good gasser, the ones that need to replace the unreliable gasser easily switch to the reliability and near zero maintenance of electric.

Ted

 

[Hippocampus]

Don’t get unreliable. As said above if you filter your gas small gas outboards are just about bulletproof. Had equivalent hours on the engine as the main (sailboat) and way more than the genset. Yamaha, Suzuki and tohatsu are excellent. The rest not so much imho.
BTW still use a Seagull that was my dad’s. Admittedly in fresh water. But the thing is older than most people on this forum and still goes and goes. Trick for that one is to never use alcohol contaminated gas in it and always run the carb dry after use. For our most recent fuel injected 4 stroke Suzuki only inconvenience was to flush it with fresh if it was not going to used for a few weeks or months. Current small gas outboards are very low maintenance, slip gas and are extremely reliable. Especially true for current fuel injected 4 strokes. Just get good fuel, a good filtering system and a set of bunny ears if used infrequently. See the unreliable comment over and over. When questioned one of the three things above wasn’t attended to or it’s an old engine.

 

[Nomad Willy]

psneeld wrote,
“ comparing electric to gas is still mostly an exercise in what one wants....not what is "better", "more practical"...etc...etc..”

What the elephant in the room may be is what one wants to be seen with.

 

[psneeld]

psneeld wrote,
“ comparing electric to gas is still mostly an exercise in what one wants....not what is "better", "more practical"...etc...etc..”

What the elephant in the room may be is what one wants to be seen with.

I don't think so...most of us are pretty practical when it comes to this discussion...there are just a varied way that people use dinghies.

Anyway.... if you are headed for E tech over petroleum...please don't. More politics in this forum is definitely a bad idea.

 

[Nomad Willy]

I don't think so...most of us are pretty practical when it comes to this discussion...there are just a varied way that people use dinghies.

Anyway.... if you are headed for E tech over petroleum...please don't. More politics in this forum is definitely a bad idea.

What on earth do you think about my post is political?

 

[O C Diver]

Don’t get unreliable. As said above if you filter your gas small gas outboards are just about bulletproof. Had equivalent hours on the engine as the main (sailboat) and way more than the genset. Yamaha, Suzuki and tohatsu are excellent. The rest not so much imho.
BTW still use a Seagull that was my dad’s. Admittedly in fresh water. But the thing is older than most people on this forum and still goes and goes. Trick for that one is to never use alcohol contaminated gas in it and always run the carb dry after use. For our most recent fuel injected 4 stroke Suzuki only inconvenience was to flush it with fresh if it was not going to used for a few weeks or months. Current small gas outboards are very low maintenance, slip gas and are extremely reliable. Especially true for current fuel injected 4 strokes. Just get good fuel, a good filtering system and a set of bunny ears if used infrequently. See the unreliable comment over and over. When questioned one of the three things above wasn’t attended to or it’s an old engine.

I'm sure most of reliability is a function of preventive maintenance. Simple fact is that there's a lot more to go wrong on a gasser outboard than electric. Last summer I towed two dinghies and saw a couple more than were being rowed. This was on Lake Champlain inside the Burlington breakwater. This is not a big deal as going from the day moorings to the dinghy dock is at most 300 yards. The two I towed were no starts, so anyone's guess whether it was stale fuel, water in the gas, or something in the ignition. On the lake you can't be out of sight of land. So I'm guessing PM on the dinghy outboard isn't a high priority like if your traveling to some remote areas in the Caribbean.

While I really liked my Suzuki 15 HP with fuel injection and electric start, it wasn't PM free. Annually I changed the engine oil, oil filter, lower unit oil, inspected the raw water pump impeller, spark plugs, anode, and changed the external fuel separator filter. After every brackish or saltwater use I flushed the raw water cooling system with freshwater.

With my Epropulsion, I rinse it with freshwater as needed and inspect the anode annually.

Now I realize I'm OCD when it comes to PM on the Suzuki, but that's pretty much the recommendations of the owner's manual. Then there's the part about keeping a box of spares for remote cruising. Very different with an e outboard.

Ted

 

[Hippocampus]

Ted you make a very valid point and can’t argue with it. That was our program as well except for the frequent fresh water flushing. Only did that on rare occasion before periods of non use. For us that meant 3 hours twice a year given that engine was used so frequently. Before going long term it was once a year. Don’t consider that a lot of maintenance nor onerous.
Big drop in maintenance and troubles came with switching away from carburetors and being meticulous about filtering fuel to ensure no water or particulate. Agree things may change now as ETOH is hygroscopic. May need to change filters more often. Still don’t consider that a biggie.
Agree with the consensus here. If you need to get up on plane with 4 people or 2 and heavy stores gas still makes sense. Otherwise as long as range isn’t an issue E is a very viable alternative.
The other side of the story is I had multiple occasions of giving e propulsion dinghies a tow back to their boats after they went off snorkeling or wandering. Even one occasion from le Marin to St Anne as the trip back and forth with a grocery load was too long for them. Don’t think e propulsion is viable for a cruiser if you’re anchoring out, exploring and need the range. We’re nearly due for a new land vehicle. Want a 4by midsize pickup. Same problem - will use if off grid and for long trips. Currently have 720m range with my diesel. Getting fuel is a 10 minute stop available just about everywhere. Want a e vehicle with a petrol backup. Market is hybrid, full petrol or full battery. Although mixed (either, or, both) is available for SUVs and cars isn’t yet for pickups. Will wait a year.

 

[NEtrawler58]

I could take Willy's post 2 ways. He could be saying that some boaters may want to appear to be green-minded by using an electric boater. It could also mean that some boaters want to be seen in the latest fastest most expensive fancy dinghy when something more simple would fill their needs. I don't see anything political about it unless you are interpreting it that way.

 

[NEtrawler58]

The big generalizations made in these opinion threads really leave things wide open for interpretation.

I think generalizations are always going to be the case in threads like these. There will always be someone that can point to a specific example that counters any comment. Like you, I have hung out in my dinghy rafted up with hundreds of others listening to an on-water music event. My yacht club will also coordinate dinghy cruises to a nearby beach for a day party and back. I just mean "IN GENERAL" I am not likely to use my dinghy more than my main boat regardless of gas prices. They serve entirely different purposes and are not interchangeable.

 

[Hippocampus]

What I’d really like to see is a dinghy/e propulsion setup designed from scratch. In other words designed to take full advantage of the benefits of e propulsion. Torque and HP curves just about parallel to each other. Suspect it would be an Al floor inflatable or all Al with some flotation added. Low down 150-200lbs of battery. Either traditional shaft and rudder or steerable prop. That would get around the range and power issues. Charge it at night. Low maintenance. 10-12’ size. Surprised not done yet.

 

[rslifkin]

I like that idea. I think that right now, the market for it would be limited just due to cost.

I've been picking out propulsion for our dinghy (12 foot aluminum skiff). At this point, I think I've settled on going with a small-ish (6hp) gas outboard. Because it's a more efficient hull than an inflatable or RIB, 6hp with an appropriate prop will plane 2 adults, although with speeds in the low to mid teens, nothing overly fast. But it'll also be nice and efficient. From the data I can gather online, it should be good for 35 - 40 nmpg when putting along at 4 kts and ~25 nmpg at planing speeds with 2 adults.

That means with a 3 gallon tank, assuming 1/3 reserve, the dinghy has a range of about 50 nautical miles before refueling on plane or 70+ nautical miles at slow speeds. That's more range than I could ever need and likely enough that I can avoid carrying extra dinghy gas on board, as we can just splash some in the tank when we go to the fuel dock with the big boat (or if we really use the dinghy a ton, just stop by the fuel dock or carry the tank ashore).

Electric would be nice, but for how little gas the above setup actually uses, I can't see it being worth it right now. A 6hp Tohatsu with the 3 gallon tank can be had for about $1600. Looking at electric, the large battery Torqeedo is almost $3000. The Epropulsion Spirit can be had for $2500 and has a slightly larger battery than the Torqeedo, so that's a better comparison.

But it's still $900 more for something that can't plane the dinghy (they tested on a similar 12 foot aluminum skiff and topped out at 5.4 kts). From their data, at ~4 kts, it would be good for about 20 miles, which is not bad. It's nice and quiet, but unless I had no desire to ever plane the dinghy, the price vs performance just doesn't quite work yet. For a dinghy that can't plane well anyway, the electric (while expensive) becomes a much more compelling choice.

The electric would be lighter at 42 lbs for the Epropulsion, vs 55 lbs for the Tohatsu 6hp + 25 lbs for the filled gas tank.

I figure at this point that we'll go for the gas option and hope that by the time I have a reason to buy another outboard for any reason electric options will improve in power (and battery capacity to allow usable range at higher speeds).

 

[Nomad Willy]

i could take willy's post 2 ways. He could be saying that some boaters may want to appear to be green-minded by using an electric boater. It could also mean that some boaters want to be seen in the latest fastest most expensive fancy dinghy when something more simple would fill their needs. I don't see anything political about it unless you are interpreting it that way.

exactly

 

[Group9]

I disagree with HGD who claimed that the IC engines ".. are extremely unreliable, never start when you need them, they are now so heavy it is almost impossible to drag them to a shop". Modern IC outboards are extremely reliable, as evidenced by their extensive use in commercial applications. In the past 30 years I've never had a no-start on my outboard, never. I agree that weight is an issue with 4-cycle OB's but this has improved with newer designs. However you must also consider battery weight with an electric. Most electrics are very low power (1-3HP). These get by with a good sized deep cycle battery (if you can recharge regularly). Speeds are quite limited with this power level. If you are absolutely sure your use is limited to sheltered harbors and short distances that may be fine. However if you cover larger distances, need more speed, or depend on the dingy as a lifeboat then electrics become quite problematic.

The primary issue with an electric outboard isn't the electric outboard itself, they're quite simple. The problem lies in energy storage. Batteries have a very low power density compared to gasoline (or any HC fuel). To put it in terms of electricity a gallon of gasoline has roughly 33 KWh. A really good deep cycle battery may have 125Ahx12V=1.5KWh. Thus the problem is obvious. In order to provide more than nominal power to the outboard the battery requirements quickly become impossible for a dingy. Even the equivalent of a single gallon of gas would weigh hundreds of pounds. As I said if you are 100% sure that the only conceivable use of dingy is short distances in relatively serene conditions then they're a convenient choice. However if you expect to cover more than a nominal distance, encounter adverse conditions, or possibly consider the dingy as a lifeboat, electric outboards quickly become uncompetitive.

I guess part of it is background. If you ever saw the movie "Mud" with twelve year olds boys running the rivers in their jon boats and small outboards, that was me growing up. I learned how to make a two cycle outboards run right before I learned almost anything else. I've owned a dozen of them, and the only time I couldn't fix right away (and never really got it running right), was an old Wizard outboard that someone gave me.

A two cycle outboard has got to be one of the simplest mechanical devices ever invented. Although I admit, an electric motor would be even simpler.

 

[NEtrawler58]

I guess part of it is background. If you ever saw the movie "Mud" with twelve year olds boys running the rivers in their jon boats and small outboards, that was me growing up. I learned how to make a two cycle outboards run right before I learned almost anything else. I've owned a dozen of them, and the only time I couldn't fix right away (and never really got it running right), was an old Wizard outboard that someone gave me.

A two cycle outboard has got to be one of the simplest mechanical devices ever invented. Although I admit, an electric motor would be even simpler.

I don't disagree with you, however, you can't buy a new 2 stroke in the USA anymore and it wouldn't surprise me if they become illegal to use before much longer. It wasn't until I bought a new 3.5 hp 4 cycle Merc that was a POS and drove me to electric. ( Anything larger than that is too heavy to handle manually for me getting it on and off the dinghy.) I also grew up on lakes and rivers with a 6 HP Evinrude on a 12 ft aluminum rowboat. Never let me down once.

 

[Group9]

I don't disagree with you, however, you can't buy a new 2 stroke in the USA anymore and it wouldn't surprise me if they become illegal to use before much longer. It wasn't until I bought a new 3.5 hp 4 cycle Merc that was a POS and drove me to electric. ( Anything larger than that is too heavy to handle manually for me getting it on and off the dinghy.) I also grew up on lakes and rivers with a 6 HP Evinrude on a 12 ft aluminum rowboat. Never let me down once.

Yep. I think way more than half the people I know with small 4 cycle outboards are constantly trying to keep them running. But, there is a huge stash of used 2 cycle outboards out there!

 

[DaveS]

Electric motor

We purchased a small blow up dingy for use where our large one was too big to launch usually from a swelly beach in Mexico where we were cruising until recently. We too bought the e motor 3hp the author did here. It is comparable to the Torquedo. We sold it and bought a 6hp gas. The electric was gutless and made getting off the beach a wet mess. Also as you cannot heart the silent electric, you never knew what it was doing. We much prefer the gas motor. Electric would be good for putting around the marina.

 

[rgano]

Actually I find it harder to believe you could find a new carburetor for a 24 year old anything.

Ted

Apparently not. I sold my old but rarely used Nissan 9.8 2-cycle to my brother who resolved a starting issue (over ayear after I handed it over to him) with a new carb he had no trouble finding online. He is carrying a spare carb now since that seems to be the most common failure point. They are quick to swap out.

 

[Helmsman]

Its probably best to make sure we understand the physics behind this comparison This gets the comparison away from opinion and anecdote and onto a solid technical footing. From a mechanical engineering POV (which is my training) the comparison is pretty simple. It is based on energy storage capacity and the efficiency of energy conversion to motive power. These factors dictate how much power you can extract and thus dictate speed and range.

The difference between an electric and IC outboard is primarily a difference in how the energy is stored and then converted to propulsion. An electric motor is more efficient at energy conversion, about 90%, than an IC engine at 20-35% (I use 25% in calculations). An Otto cycle engine will vary efficiency depending on load, they're most efficient at full power. An electric doesn't care much.

However this is only half the story, the other half is energy storage. In this batteries suffer. The best current batteries, Li-Ion, have 50-250Wh/kg of energy density with 100Wh/kg appearing to be typical of what's on the market (higher density get into cooling requirements). This looks good compared to lead acid which are 30-50kWh/kg. However, gasoline is the equivalent of 9444 Wh/kg. There is an additional confounding since you can't pull all the energy out of a battery as you can with a liquid fuel. So using round numbers you need about 250lb of battery for each equivalent gallon of gasoline (depending on how far down you can pull the battery this could increase a bit, if batteries improve some it goes down a bit)

The comparison that drives range and speed is the available energy times the efficiency of energy conversion. Based on this gasoline provides 10-25 times more available propulsion energy per unit weight of energy storage than state of the art batteries, even with the lower efficiency of the IC engine. The higher number is actually more realistic today without cooled batteries.

None of this is intended to dismiss E-outboards out of hand but to allow one to make a comparison on an equivalent basis. Based on the physics it is impossible to say an e-outboard is equivalent to an IC outboard overall. The limitation on going up on power for a e-outboard is fundamentally the battery weight. The equivalent of a 6 gallon tank of gas that is 50lb becomes about 450lb (compensating for energy conversion efficiency of the motors otherwise you're at 1500lb). Hence the tendency for e-outboards to be lower power since then you can keep the battery weight compatible with the capacity of the dingy and the ability to bring the battery aboard the main vessel for charging. Obviously this comparison will continue to improve as battery technology evolves with solid state being the next horizon, we'll have to see what that brings us.

Thanks. That puts the discussion onto perspective.

 

[High Wire]

My about to turn 50 YO, 1973 Evinrude 6 hp starts cold on the second pull and warm on the first. Yes it does smoke a bit at idle but with two pistons it’s nice and smooth. Whopping $300. The Tohatsu 5hp needs choke to start if not run for the past few hours and smokes for the first 30 seconds or so cold. After that it’s great on gas. Would be nice if it had a balance shaft. And it won’t tilt in neutral by design! What the heck?

 

[kthoennes]

I mentioned above it's been a breeze to get parts for our 35 year old Yamaha 4HP two stroke, even lately. It is kind of amazing. It does take some maintenance to keep it running smoothly - new flapper gasket in the carburetor, new in-line fuel filter every season. I did spend a number of hours in my shop in the middle of winter disassembling, reassembling, tuning up and learning that motor when we first got it, out of a guy's grassy backyard in Clinton, CT. Just excellent design. That thing might run forever, or at least until I'm dead. You can hop on Craigslist or FB Marketplace just about anywhere in the country and find ancient 2-stroke outboard motors that do or could still run with a little care.

In this world of what seems like intentional obsolescence - "we regret to inform you we have discontinued product support for..." anything that keeps running like a champ for decades is oddly satisfying.

 

[47Rah1980]

What I’d really like to see is a dinghy/e propulsion setup designed from scratch. In other words designed to take full advantage of the benefits of e propulsion. Torque and HP curves just about parallel to each other. Suspect it would be an Al floor inflatable or all Al with some flotation added. Low down 150-200lbs of battery. Either traditional shaft and rudder or steerable prop. That would get around the range and power issues. Charge it at night. Low maintenance. 10-12’ size. Surprised not done yet.

I have this being delivered soon. No previous dinghy or perfectly working gas engine to replace. Expensive but this will be fast when needed.
https://www.purewatercraft.com/product/rib-classic-360

 

[Bmarler]

I have this being delivered soon. No previous dinghy or perfectly working gas engine to replace. Expensive but this will be fast when needed.
https://www.purewatercraft.com/product/rib-classic-360

i love that. didn't know it even existed, but it makes perfect sense. wish it was a little cheaper. i'm kind of over how companies that sell e-propulsion always lump in that the fact you don't need to purchase gas makes them actually cheaper in the long run.

 

[NEtrawler58]

i love that. didn't know it even existed, but it makes perfect sense. wish it was a little cheaper. i'm kind of over how companies that sell e-propulsion always lump in that the fact you don't need to purchase gas makes them actually cheaper in the long run.

Looks like another great advance in electric boating. Electrics can be cheaper than gas in the long run, but it's not just in the cost of fuel but also in maintenance costs. I know lots of you want to yell at me that you do your own maintenance and it only costs a few dollars. The point is that there are studies that show the break even point of some electric motors ( 7 years or so). You can agree or not. I'm not supporting or defending that claim, so no need to debate it with me.

 

[Hippocampus]

I have this being delivered soon. No previous dinghy or perfectly working gas engine to replace. Expensive but this will be fast when needed.
https://www.purewatercraft.com/product/rib-classic-360

That looks awesome. Please post afte you have some miles on her.

 

[rslifkin]

That thing does look cool! Price aside, the only thing I see about it that's not ideal is the weight.