eGuardian 420 electric safety boat with Mitek 6hp has 45nm+ range!

Range anxiety? What range anxiety…..

We went out testing the eGuardian 420 electric safety boat and will be running a series of tests using a variety of batteries and Mitek motors for which we are the sole UK distributor:

https://www.electric-outboard.co.uk/brand/mitek/

These 48v motors are based on standard Yamaha compatible powerlegs and therefore use standard props available from any outboard supplier. This means you are using tried and tested, very robust props and are not dependent on very expensive and brittle plastic propellers.

This is particularly useful when in a more commercial application such as rental boat fleets or safety boats for water sport clubs as these boats have far higher than normal usage.

With the much reduced requirement for maintenance and minimal running costs (especially where you might have cheap overnight charging) these motors are changing the face of what is possible with electric boating!

The Mitek motors also buck the trend of many manufacturers to overstate the power – many smaller electric outboard motors will claim to be a 3hp equivalent even when they are only a 1Kw motor. With the approximate ratio of 746w to 1hp we can see that a 1Kw motor is more like a 1.3hp motor.

Electric motors often deliver their power very differently though as they tend to run much slower rpm and have a much larger prop than you would expect – they make the most of the instant full torque so have a good bollard pull but run out of steam when trying to go faster so unfortunately, people often feel let down if this has not been clearly explained to them.

The Mitek motors on the other hand give a much closer approximation of their  horsepower – for example this motor is rated at  4.3Kw so dividing by 0.746 give you 5.76hp so 6hp seems fair enough. The Mitek 9.9hp is rated at 7.2Kw so this is 9.65 – again close enough to be more realistic.

Just as importantly, the motors rev up like you would expect with a petrol outboard – while many 1Kw consumer type models rev to around 1,500 with their larger props, the Mitek will rev to over 5,000 rpm. Along with using an identical prop you actually get the same experience without the noise, smell or direct pollution of a petrol outboard!

Lastly, as you go up the power ratings, for many motors the submerged motor unit starts to become quite a constraint. As a boat increases speed, the water passing over the motor unit gets very disturbed before it reaches the prop decreasing efficiency and overall performance.

The standard smaller and very streamlined powerleg of the Mitek motors reduces this turbulence and drag significantly, enabling greater performance at higher speeds.

We have a video here showing a good chunk of the test:

YouTube player

and have many more planned for this season assuming it manages to stop raining and blowing agale again at some point!

If there are any motor/battery combinations you want us to test please let us know – you can always book to come and visit us for a demo and we also travel out to clubs for dedicated demo days.

Anyway, for this test we had the Mitek 6hp 4.3Kw long shaft electric outboard motor. Powering it we have two of our 48v 150Ah Eco Power Max battery packs totalling 15Kwh of capacity.

The eGuardian 420 is fitted out with our modular console that incorporates the batteries under the large twin seats and there is the steering console and top storage locker, however as the Mitek 6 motor is a tiller control the console in this test is just a perch for Lesley to sit on during these tests.

The dashboard has a Renogy digital coulomb meter rated to 500 amps to accurately track the battery usage and give a clear display in any conditions.

The batteries each have a BlueTooth BMS and we will be checking the calibration of the Renogy meter as we deplete the battery.

The display has a “time remaining” feature for your current consumption which as it is based on very accurate coulomb tracking will be very helpful when out on the water.

We are looking at how we can potentially build in some spare capacity by manipulating the battery BMS parameters such that some reserve of say 10% could be unlocked out on the water using the phone app.

As ever, simply going slower will extend the range and the data we collected from this test clearly demonstrates this.

The eGuardian in this setup using the Mitek 6hp (4.3Kw) motor is towards the bottom end of the possible specifications – we can go down to the Mitek 4.5hp (3.3Kw) and it works fine and even the Mitek 2.6hp long shaft moves the boat around quite happily. However, for a bit of extra oomph and the ability to tow boats, we think this is realistically the smallest motor you should probably go for.

The boat is pretty well loaded up for this test as we have:

Bare hull inc swim ladder: 185kg

The steering console / seat  / battery unit: 45kg

300Ah of batteries: 135kg (inc cabling)

2 crew: 145kg

RemigoOne motor and chargers etc: 20kg

Total: 530kg

We would expect most people using a smaller motor like this one might have either one 100Ah or one 150Ah battery perhaps, or 2 or 3 50Ah batteries for easily removing them from the boat if this is required.

With the tiller steering then there would only normally be a small integrated thwart / battery storage which weighs around 15kg and quite probably only the driver so the weight of the boat might be down to around 355kg – we will do some videos with a similar setup so people can see exactly how that works.

The boat is clearly never going to plane with the weight and small powered motor so we are going to do battle with the infamous hull speed problem!

So the hull speed can be found using this handy online calculator: https://www.omnicalculator.com/sports/hull-speed

and it shows the hull speed for a 4.2m boat is essentially 5 knots. From years of testing small boats we think aiming for around 75% of a given hull speed gives a really good range while maintaining progress – in this case this would be around 3.75 knots.

Once you start getting closer to hull speed, then you see that you start building up more wake and a bigger bow wave while not really going much quicker.

So it is clear that until we start planing we are simply pushing more and more water out of the way, and as water is approximately 830x denser than air, we can see why range will drop off significantly as we simply waste fuel moving water not the boat.

Once we can get planning with more powerful motors, then speeds will pick up markedly but there is a very tricky area between around 5 knots and 12 knots for this boat / configuration where it will simply become more inefficient as you increase power the same as a petrol engine would.

We believe that having some awareness of peak efficiency is a great thing for electric outboards particularly, but it does also apply to petrol outboards, cars and so on.

So for this test we simply wanted to baseline the boat going up and down Lymington River at some set power levels to get some indicative data.

The weather was overcast with a cold westerly wind coming in that sat around 9-10 knots gusting to 15-16 knots in the marina and where we went out on towards the Solent it was blowing around 20 and gusting into the low 20’s.

2024-04-14 Weather Conditions

The boat will pull a maximum of 90 amps at full power so we wanted to run up and down against the tiny bit of tide (that was still just about coming in) to get some approximate speeds for each power setting.

We therefore aimed to start running at circa 20 amps then going up in 10 amp steps. However we only had limited time so only briefly got to 50 amps and will look to finish the test as well as do a longer run as soon as we can.

So we had:

  • our usual Garmin GPSMAP 86S
  • the Mitek app on our phone
  • the app for the battery BMS
  • the Renogy display reading from the battery shunt
  • 3D Insta360 camera

The Mitek app connects to the Mitek 6 motor using the optional Bluetooth connection box which sits inside the head unit and shows the motor rpm and speed along with the power being consumed.

There appears to be a little discrepancy between the Garmin and the Mitek app but we will use the same process for all tests so it will be easily comparable.

We had a nice potter about up and down the Lymington River going out towards the Solent then heading back down to Lymington Quay then back up out towards the Solent a couple of times and we covered 2.7 nautical miles in around 50 minutes averaging 3.45 knots over the course.

From GPS data we have gathered from various clubs, the average speeds tends to only be around 2-3 knots in many cases and distances often significantly less than 5 miles in a session.

The data from this first run is summarised as follows:

20 amps 1,000w 3.3 knots      15 hours duration      45nm+ range

30 amps 1,450w 3.6 knots      10 hours duration      45nm+ range

40 amps 1,950w 4.2 knots      7.5 hours duration      45nm+ range

50 amps 2,400w 4.5 knots      6 hours duration      45nm+ range

Here is the overall track of our short test:

2024-04-14 Overview of trip

showing we covered 2.70 nautical miles in around 45 minutes averaging 3.4 knots.

Here is the live page showing the original data so you know nothing is being manipulated:

https://connect.garmin.com/modern/activity/14913232171

Here is the Garmin GPS track for the 20 amp section:

2024-04-14 Garmin GPS tracks to solent and back 20 amps 950w

The first section to around 10 minutes was going out towards the Solent at 20 amps (1,000w) and then through to around 18 minutes was at the same power to average any effect of tide and wind and averaged around 3.3 knots (Mitek app).

2024-04-14 Mitek App 20 Amps 1,000w

and this shows the prop speed at 2,366 rpm.

From then to around 27 minutes we went up to 30 amps (1,450w) and went to Lymington Quay and then back up to the launch ramp at Lymington Town Sailing Club averaging around 3.6 knots (Mitek app) through to around 35 minutes.

2024-04-14 Mitek App 30 Amps 1,450w

and this shows the prop speed at 2,786 rpm.

We then went up to 40 amps (1,950w) and headed out towards the Solent and back (shorter run) which took us to around 40 minutes averaging 4.2knots (Mitek app).

2024-04-14 Mitek App 40 Amps 1,950w

and this shows the prop speed at 3,150 rpm.

The last short run before heading back in was at 50 amps (2,450w) again out towards the Solent and back to the ramp and this time we averaged around 4.5 knots but annoyingly I didn’t take a screenshot from the Mitek app!

From all of this data we already start to gather together some useful inferences.

The motor is super smooth and picks up very nicely delivering power very easily.

Doubling the power from 20 amps to 40 amps adds 0.9 knots to the 3.3 knots at 20amps – the 100% increase in power consumption gives a 27% increase in speed and shows the very significant effect of going over our rather arbitrary 75% of hull speed threshold.

This also reduces the range from over 45nm and reduces it to around 30nm+ – still very significant!

When we go back out testing we will see incrementally smaller increases in speed as we go up the power range and simply start shovelling ever more water out of our way.

Therefore it is important to note, as we always bang on about – when you can, be careful with your power but when you need it then the motors can really deliver.

From this we can fairly readily extrapolate that a single 100Ah battery for an inland club would give a range of over well 10 miles at an average speed around 3.5 knots. Taking into account removing around 85kg of battery weight – so a full sized person – then probably more.

So two 100Ah batteries would enable probably a weekends worth of support for many inland clubs!

Charging will be addressed in some separate videos and blogs but all of our batteries can be easily charged from a standard three pin plug – a key part of battery longevity is not fast charging and so by default we suggest around 20-30 amp chargers going up to 50 amps for the largest battery packs.

A 100Ah battery can be charged on the water in 4 hours from completely empty using a 30 amp charger which can run off decent extension lead if there is no power to the shore. Don’t forget that 40 amps at 48v is effectively 40 * 57v (charging voltage) so around 2,250 watts which at 220 volts is only just over 10 amps.

So even charging two completely empty 100Ah batteries using a 40 amp charger will easily be accomplished overnight ready for another good long session out on the water.

The eGuardian 420 is also available in different sizes of 350 and 460 depending on your requirements and we can also retrofit the Mitek motors and our battery solutions to a wide variety of boats as our modular console is easily adapted by simply using the appropriate baseplate.

Many clubs require console steering for easy use by their volunteers for safety duty but we can also provide thwart based battery storage for the eGuardian if you prefer tiller steering.

The eGuardian provides a very robust, powerful and natural pathway to transition away from smelly, noisy and unreliable petrol outboard engines.

Minimal maintenance is required as the motors have very sturdy standard props and the chassis is based on proven powerleg technology developed over many years with the gearbox oil needing changing after the first ten hours use and then only occasionally..

There is no more hassle, smell and potential spillages bringing fuel back and forth to the marina / storage shed making for very easy management of your safety fleet.

We will also soon be running a series of tests using the old faithful Rigiflex 360 as we have had many requests for this so we will be developing a thwart battery box and testing with a variety of motors and batteries to the demonstrate performance capabilities.

Orders are now being taken for delivery later in the year and into 2025 but we always want to ensure that people fully understand their current safety boat usage so we encourage people to read our article on tracking you current usage with a free GPS app on your phone or any GP enabled device that can export .gpx files:

https://www.electric-outboard.co.uk/clearly-understand-your-actual-safety-boat-use/

Doing this over the course of this 2024 season will ensure that we can help you bottom out exactly the right boat, motor and battery solution for your needs.

Clubs are generally looking at replacing their slowest / oldest boats to enable them to get comfortable with this quite large change in their processes and procedures and will then factor in a boat every couple of year in many cases.

Quite a few clubs will retain their highest power petrol outboards for many years yet, but any petrol motors that we can remove from our waterways can only be a good thing for our aquatic environment.

If you are interested in having a demo of our eGuardian or bringing along some kit to test on your boats, please feel free to contact us as we constantly travelling around meeting with clubs.

If possible we like to pull together a number of other local clubs at one host club so we can give some question and answer sessions and then have some time out on the water to understand the boats.

Please contact us using:

[email protected]

01590 619315

07863 403462

And we look forward to helping you keep your sailing environment as clean and safe as we can!

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