A dinghy is a useful, and in some cases, necessary accessory for a cruising boat. I haven't yet started cruising, but it seemed that it might be fun to have, and could certainly be useful for short trips where we might anchor out.
I ended up buying a West Marine RIB 310, single floor, PVC dinghy. Comparatively speaking, this was a readily accessible model with decent features, at a competitive price (I got it on sale - though this summer it went on sale for even less).
We also looked at the 8' Takacat. The Takacat is fully inflatable - so that you can deflate it, roll it up, and put it in storage (out of sunlight) when not in use! That was a huge selling point. The marketing claims that it handles waves really well. Unfortunately, we found the 8' version it to be just too small to comfortably fit two "full sized adults". We also found that we couldn't comfortably row the 8' Takacat with two people in the boat. In hindsight, it would be interesting to comare the 10' Takacat to the West Marine RIB 310. At the time, the 10' Takacat was not considered, as it was thought to be too large to comfortably fit on Sunset Dream's dinghy davits.
We have a friend that had an 8' hard plastic "Portland Pudgy". Neat boat, very distinctive. The pudgy has many accessories that allow it to be configured to motor, row, sail, and even serve as a life raft. Unfortunately, the Portland Pudgies are very expensive, and not readily available in my location (Texas). After testing our friend's boat, we came to the conclusion that an 8' dinghy was just too small for two "full sized" adults.
9-4-22 Tested Portland Pudgy with 12V trolling motor and 150Ah lithium battery going around Clear Lake Shores Island. Out for about 2 hours, after having rowed quite a bit of the way back, due to concern about the battery running low. Had to run the trolling motor at top speed (5) to make progress in the Clear Lake channel against a strong tide.
9-24-22 Tested Portland Pudgy with 24V Torqeedo, 50Ah 24V Lithium battery. Motored to Schaffer's at low to med speed, about 3mph. Did great - out for about 1.5 hours with power still left.
We finally settled on the West Marine RIB 310. The Vee bottom should provide more stability and wave handling than the flat bottom, fully inflatable versions. (There are tradeoffs with everything!) So, we won't be able to store it easily, but at least it will hopefully be sea worthy.
So far, our experience has been than the West Marine RIB 310 holds two people very well (our first trip was with 3 "full sized" adults, and that was fine). The RIB 310 is reasonably balanced, and very stable. We will probably never have enough horse power on board to get it up on plane. But it should easily get us from boat to shore.
The single hull version is very deep inside (more of a challenge for a "vertically challenged Admiral" than the captain...), but is lighter and cheaper than the same model with the flat interior (though the false bottom version has a nice storage locker at the front that would be really helpful for stuff that could stay on the boat).
So far - We've been very happy with the RIB 310.
6-9-23 Dinghy experiments with Torqeedo 2T 24V vs. Hangkai 48V.
7-25-23 Dinghy to Shaffer's with Hangkai 48V 50Ah battery, about 30 min to get there, about 45 min to return. Plenty of power left.
Need to understand why the trolling motor seemed to perform so poorly. Need to monitor power draw from trolling motor at various RPM and speed over ground. Is the Portland Pudgy that much harder to push with two adults, compared to the 10' RIB? Or is the trolling motor that much less efficient than the 24V Torqeedo and 48V Hangkai?
The next part of the equation was: Which motor to power the dinghy. After my prior experiments with electric power, an electric dinghy seemed natural. It's small enough to be powered by available batteries for a reasonable run time. The motors are less than 50 pounds, making them FAR easier to manage. The lithium batteries are reasonably light. While a motor, a battery, a backup battery, and a box including the power switch and battery monitor - will all add up to the same weight as a gas outboard, you can at least break it up into pieces that are easier to move on and off the dinghy.
The real beauty of an electric dinghy is that you simply turn on the switch and go. No mixing gas. No carburators to gum up. It just runs.
The obvious down side of the electric dinghy is run time. While I am setting mine up to have at least 3 hours of run time between the primary and backup battery - if I use that up, I'm simply done. There is no "just pour more gas into it and go". Gas engines unquestionably allow for far longer range, easy refills, and far greater power, if you need to go fast. But if you just want to putter around a little bit, or just get from boat to shore from time to time, an electric motor is a very capable solution - and easy for all crew members to handle.
From my prior experiments, I still had the 24V Torqeedo 2T (tiller model version). I had a single 60AH 24V lithium battery that I could use to power the Torqeedo. The issues with this are:
The Torqeedo is about a $4000 motor. All electric motors in a salt environment can expect to fail sooner or later, and replacing a $4000 motor would give anyone pause.
24V lithium batteries are expensive, not as plentiful as 48V batteries, and are hard to find in sizes that will fit standard battery boxes. A second 24V lithium battery (because you always do want to get home after you somehow drain the first battery...) cost more than a cheap Chinese 48V electric outboard - so it was compelling to buy the 48V outboard instead of a backup battery (especially considering I already had two 48V eBike batteries).
In terms of performance, the Torqeedo powers the dinghy with authority. The Torqeedo has a relatively large 3 blade prop that provides what feels like a lot of torque. The Torqeedo feels solid, and is relatively quiet. No - electric motors are not "silent". That's a myth. But it is FAR quieter than any kind of gas engine.
After trying the Torqeedo on the dinghy, and finding it to be entirely adequate for my needs (other than the expense of a backup battery, and the high cost of a replacement motor), I decided to try a 48V Chinese motor.
I purchased the 48V Hangkai 1000W motor for under $350, delivered. Less than 10% of the cost of the Torqeedo. Initial impressions:
MUCH LOUDER than the Torqeedo. The Hangkai obviously has the electric motor in the head unit, driving a shaft, like a traditional gas engine.
The Hangkai has a tiny 3 blade prop. I strongly suspect the Hangkai would do better with a larger prop. Maybe not quite as large as the Torqeedo prop, but at least bigger than the existing one.
The model I bought has no reverse! Be aware of this The advertisement in Amazon said there was a "reversing gear" - but this is not true! You have to turn the motor 180 degrees to achieve reverse. Look for the version (at least 1200W?) that has TWO buttons - one if for holding the existing speed, the second is for reverse.
As mentioned in the Amazon reviews, the throttle is too sensitive. It needs more physical range of the throttle to allow finer control of the power level of the motor. The current throttle makes it extremely difficult to pick a desired range. However, they do provide a button to allow locking of the speed - at whatever power level you currently have the throttle at. Though holding the throttle, hitting the button, and watching forward all at the same time is quite a challenge!!
There is no kill switch for this motor! The throttle is spring loaded. So, if you take your hand off the throttle - AS LONG AS YOU HAVEN'T LOCKED THE THROTTLE SETTING - the motor will stop. But most people will lock the power level if they are going any distance. If you lock the throttle setting, and manage to fall overboard, there is nothing to stop the motor. My solution to this is to wire a 48V relay between the battery and motor, and use an outboard kill switch to operate the relay. I'm wiring a volt/amp power meter in the same box with the relay and kill switch.
Impressions of the Hangkai "performance":
Yes, the motor "feels cheaper" than the Torqeedo. But for 1/10th the price, one must be willing to accept that. The reality is that (so far, and I don't have much experience with the motor yet!) - there has been no indication that it is poorly built.
It takes a bit more power to achieve the same speed as the Torqeedo. I suspect this is due to the prop being so small.
BOTTOM LINE - as long as you can accept putting around at 3-4mph, the Hangkai is an inexpensive, simple solution to driving the dinghy. Using eBike batteries, I think I can reasonably expect a range of over 2 hours on a 30Ah battery, with an extra hour of backup (emergency / get home) from a second 20Ah battery. The Hangkai 48V system with a 48V ebike battery is a much more cost effective option than the Torqeedo.
I REALLY WISH the Hangkai had the following 3 features:
Reverse! (apparently this is switch selectable on other models. I did a bad job of ordering...)
Throttle needs to "stay put" instead of being spring loaded to cut off if released. The "push to hold speed" button is very difficult to operate, and almost impossible to do with one hand while holding the speed, and watching where one is going...
Kill switch - Instead of turning off if throttle is released (which most of the time, will probably be set to "push to hold speed" mode, which then won't shut off!), there needs to be a separate kill switch with a lanyard.
On 6/9/23, a "side by side" test was conducted of the 24V Torqeedo vs. the 48V Hangkai electric outboards.
Both motors were tested on the West Marine 10' RIB with fiberglass hull. Two adults. Speed measured by Navionics. Power (watts, amps, volts) measured using a Victron Battery Monitor smart shunt.
Torqeedo Cruise 2T - 24V, 2400W max
WATTS Amps Volts Speed (knots)
200W 7.2A 26.5V 2.8k
500W 19.8A 25.77V 4.0k
800W 31.7A 25V 4.0k
1200W 47.5A 24.8V 4.8k
Hangkai 48V, rated at 1000W
Watts Amps Volts Speed (knots)
200W 3.4A 58.3V 1.5-2k
580W 9.9A 57.8V 3k
660W 11A 57.15V 3.3k
840W 14.7A 57.49V 3.7k
1000W 14.7A 57.49V 3.8k
1000W 17.6A 56.6V 3.4k (into wind?)
I'm still not excited about trying to use a Torqeedo in a salt environment. Just doesn't seem like a good idea at $4000, and very expensive 24V lithium batteries.
Last weekend (4/14/24), I hooked up the Hangkai to the 48 volt lithium batteries. Both batteries were dead. I recharged the batteries, but so far have not gotten them to run the motor. Not sure if this is a motor issue, or if leaving ebike batteries exposed (in battery boxes) to the elements over the winter was too much. We had a couple of freezes, but nothing too extreme - and the batteries were completely disconnected. The batteries had not been charged - so maybe the BMS ran them down? So far, it seems that both ebike batteries are shot. They will charge, but don't seem to be able to deliver any appreciable current. Or maybe the motor is shot? Or maybe both??
Anyway, I had also brought the 12V trolling motor back to the boat for additional testing. From my previous notes, the trolling motor on the Portland Pudgy didn't get us to Schaefer's and back without significant rowing... The 150Ah lithium battery should have been able to run the trolling motor plenty long enough to make that trip, with plenty of margin.
So - first experiment was to fully charge the 150Ah battery, and do a static battery torture test at the dock.
The trolling motor (Minn-Kota 35 pound thrust, 12V) was mounted on the dinghy. The dinghy was kept tethered to the dinghy davits. The motor was fired up to top speed ("5"), and let run.
The 150Ah battery was able to power the trolling motor at top speed for 3 hours.
From what I can tell, using the Victron Battery Monitor, with a 20% floor set, this performance was a little short of what I would expect from a 150ah lithium battery. However - it is PLENTY sufficient for operating the dinghy - at least from a "runtime" perspective.
4-15-24
Minn-Kota 35 pound trolling motor - Motor was run at full speed ("level 5") for the duration of the test.
The motor was mounted on a West Marine 10' RIB 310, that was secured to the trawler in the marina (static run test to just test the battery performance under a real electric trolling motor load).
The test was monitored on a Victron bluetooth 150A "SmartShunt" monitor. The "floor" was set to 20%, battery capacity set to 150%. Battery was fully charged @ 14.6V prior to test. Percentage in the table below is the Victron "% capacity remaining" estimate. Voltage, current, and watts are as reported on the Victron app.
5:40pm - start - battery at 100%
5:45pm 12.78V 98% 36.7A 470W
6:19pm 12.73V 83% 34.3A 438W
6:56pm 12.66V 68% 33.9A 429W 44.3Ah consumed
7:39pm 12.62V 51% 33.49A 422W 68.4Ah consumed
8:16pm 12.5V 36% 33.32A 417W 89.3Ah consumed
8:40pm 12.42V 26% 32.99A 409W 102.6Ah consumed (reported by Victron)
Victron estimated 16 min remaining to floor.
Test stopped at 8:40pm. At this point, the motor had been running constantly at "level 5" (max speed) for 3 hours.
Assuming 150Ah at avg 12.5V, and an average load of ~440W, and a 20% floor (only using 80%), I calculated that I should get about 3.4 hours. This experiment showed about3.2 hours of run life. So not bad... Not great, but close enough to the estimate to be satisfied. In this case, 3 hours of run time at full speed should be plenty for typical dinghy use.
Data collected on 4/20/24. overcast skies, about 75-80F, breezy. The motor was mounted on a 10' West Marine RIB 310, single floor RIB with fiberglass hull. Due to wind conditions, most of the data collected below was running back and forth in the fairway behind the trawler in a reasonably protected area.
Speed was recorded using Navionics - speed recorded in knots. Motor power used was monitored with a Victron 150A SmartShunt. The battery was the above Eco-Worthy 150Ah 12V battery, that was fully charged before this and experiment.
Motor Level Speed (Knots) Power used
5 2.3kn 410W
4 1.5kn 230W
3 1-1.3kn 160W
This motor was purchased new on Amazon. $216 including tax. 12V, 5 power settings, 50A max.
Motor Level Speed (Knots) Power Used
5 3kn 550W
4 2.1kn 290W
3 1.7kn 245W
General comments:
The Newport "Canoe Style" trolling motor has a 3 blade prop instead of the 2 blade on the Minn-Kota. At 55 pounds thrust, it does seem a bit more authoritative than the 35# Minn-Kota.
The Newport motor was very quite, very smooth - nice to use! The 24" shaft lenght fits the dinghy much better than the 36" shaft length of traditional trolling motors.
While the recorded speed difference doesn't look like much on paper - it did "feel" a bit faster.
Motor Voltage Max Speed Max Power
Torqeedo 2T 24V 4.8Kn 1200W** (Motor testing limited at 1200W due to battery limits)
About $4000, rated at 2400W
Hangkai 48V 3.8Kn 1000W About $330, Rated 1000W - VERY Noisy
Minn-Kota 35# 12V 2.3Kn 410W
Newport 55# 12V 3Kn 550W About $200, Rated 50A@12V
Summary thoughts:
For speed and power, the Torqueedo 2T was clearly on top. Unfortunately, the 24V Torqeedo is about $4000+. Finding 24V batteries that fit in a standard battery box is a bit of a challenge, but do-able. Currently, they are running about $300 for a 60Ah battery. Torqeedo offers other smaller motors with integrated batteries - but they are still have about a $2000-3000 price tag, and spare batteries are VERY expensive.
The Hangkai is a VERY cost effective answer for a 48V outboard electrict motor. However, this motor has a VERY touchy throttle, is extremely noisy, and didn't perform significantly better than the 55# Newport trolling motor.
While the Newport 55# won't get you anywhere fast - it does seem to do a decent job, and should be sufficient for getting the dinghy from boat to shore (as long as there isn't a strong/fast current). 12V lithium batteries are easy to obtain, and a very common voltage to work with. Overall bang for the buck in terms of a nicely performing, low cost motor with an easy to purchase / replace battery seems to be the Newport. Just don't be in a hurry.
($230, July 2024 Amazon)
I bought a 100Ah Eco-Worthy LiFePo4 battery as a backup for my dinghy. Back of the envelope guess was that this should provide me as much as 2 hours of run time at full speed on the Newport 55# trolling motor. That turned out to be about right - at least with the battery new out of the box, calm test conditions with the dinghy tied to the back of the boat.
The data below is for the first torture test. As mentioned, this was run with the motor set to full speed ("5"), mounted on the 10' West Marine Dinghy, with the dinghy in the water, secured to the back of the boat. I was only able to run the test for 1.5 hours before needing to stop (scheduling, not related to the test). Several hours later I continued the test. I ended the test at about 2h 15m of run time, with the battery depleted below 12V. The BMS did not stop the battery.
NOTE: The Percent Charge (*) was set in the Victron battery monitor for a 150Ah battery, with a 10% floor. This was a 100Ah battery - so % charge will clearly be off (high).
Time Volts Amps Power TotalAH TimeRemaining Percent Charge* (based on a 150Ah batt)
Rest 14.0 .21A 3W 0Ah 10D 100%
2:00pm 12.49V 49.1A 609W 1Ah 3h2m
2:02 12.4 45.49 562 3.8 2h19m
2:15 12.41 44.68 553 13.6 2h10m
2:30 12.4 43.6 533 24.7 1h58m 82%
2:45 12.37 43.97 544 36.0 1h41m 74%
3:00 12.35 43.59 538 47.2 1h26m 66%
3:15 12.33 42.75 529 57.6 1h13m 58%
3:30 12.29 42.18 518 68.3 59m 50%
Test stopped.
Resting 13.7 .18A 2W 69.6Ah 49%
Testing restarted (without charging battery - picking up from above)
Resting
7:27pm 13.15V .22A 3w 69.6Ah 49%
7:30pm 12.35V 47.7A 588W 70.4Ah 49%
7:40pm 12.26 41.7 518 77.4 44%
7:45 12.24 40.5 493 80.6 43m 41%
7:50 12.2 40 488 84.1 39m 39%
7:55 12.2 40.17 487 87.6 33m 36%
8:00 12.07 40.4 484 90.8 29m 34%
8:05 12.02 40.1 482 94.2 24m 31%
8:10 11.87 39.46 469 97.7 19m 29%
8:15 11.3 34.12 389 100.7 16m 27%
Stopped Test
8:30 (Resting) 11.8V, 0.17A, 2W 101.1Ah 27%
Conclusion:
The battery did seem to deliver a minimal 100Ah of power - though this was taking the battery to a low voltage.
Note that the current output of the battery dropped off as the battery drained. It is possible that the characteristics of the motor changed as the motor heated, but that should not have affected the amount of current drawn.
From previous "speed" tests with the Newport motor on the West Marine dinghy (relatively calm conditions), the dinghy ran at about 3 knots at full power, at about 550W (full battery power). By the time the battery has been run for about 1.5hr (approximately what I would plan to be a max planned run time for this batter and motor), at full speed, the battery will only be delivering about 520W. As the battery drains further, speed will most likely be reduced by up to 1/2 knot.
Time Volts Amps Power TotalAH TimeRemaining Percent Charge* (based on a 150Ah batt)
REST 14.41 0.21A 3W 0Ah 10D 100%
10:30am 12.89 49.9 635 .4 5h 100%
10:32 12.54 46.7 584 1.2 2h53m 99%
10:35 12.46 45 562 3.3 2h22m 98%
10:45 12.51 41.6 514 10.3 2h26m 92%
11:00 12.46 42.5 530 20.8 2h6m 85%
11:30 12.43 39.9 507 41.5 1h42m 70%
12;00noon 12.34 41.0 506 62.3 1h10m 55%
12:30 12.2 39.8 485 82.3 42m 40%
12:45 12.03 39.26 472 92.2 27m 33%
1:00 10.97 39.09 373 101.1 16m 27%
Running voltage dropped to 10.7. Test stopped.
Resting voltage 11.23V
8/18/24 - John and Donna took West Marine dinghy to Schaffer's. Ran Newport trolling motor at highest speed (5) the entire trip. Only used the Eco-Worthy 150Ah battery (did not need to sub in backup battery). Speed about 2.2 knots by Navionics (about 3mph by Waze - though 2.2 knots converts to about 2.5 mph).
Left boat/dock at about 5:30pm. Arrived at Schaffer's at about 6pm. Used about 20-22 AH, battery at about 87%
Took "the long way" up through the canal and back through the Kemah channel to return.
Left Schaffer's about 6:50-6:55. Arrived at boat about 7:50pm. Total trip consumed about 49Ah. Battery at about 87% capacity. Resting voltage was at 13.15.
Plenty of battery capacity in 150Ah battery to run 2 hours on full speed with Newport motor.