Electric Outboards

[Graham W]

John,

I rest my case!  If a petrol engine with a supposedly lower output can do it but the Torqeedo can't, there's something not quite right about the Torqeedo's alleged specifications.

[Peter Taylor]

After my first year of using my BC20 "Seatern" I wrote my conclusions with regard to equipment performance including the Torqeedo which I had rapidly abandoned in favour of a 6hp Tohatsu with higher thrust propeller. You can find my notes at http://www.seatern.org.uk/SeaternDiaries/equipcomments/torqeedo.php.  I suspect my most pertinent comment was as follows...

"Thrust: When I have used the [Torqeedo] in strong winds on my Seafly dinghy, it appears to lack thrust. At full power in calm conditions it can push the racing dinghy at 6 kt which is nearly planing speed. But in high winds it fights to keep the boat on course [...that is even at slow speeds]. For Seatern, even in calm conditions full power only achieves just over 4 kts. I interprete this as lack of thrust. I don't understand the propeller specifications quoted by Torqeedo, but those for the 1003 propeller seem to be more similar to those for the alternative propeller sold for their larger "Cruise" motors for "planing applications with lighter boats". To my mind this lack of thrust compounds the lack of power problem and made me reluctant to take Seatern out if I may have to contend with strong winds while under motor."

I concluded that the Torqeedo was at best equivalent to a 2hp outboard.  Graham's 2016 Raid experience suggests that I was being overly optimistic!

Peter

[maxr]

Any updates on recommended engines for BR or BRe, guys? I read that there's now a high capacity 915Wh battery available for the Torq 1003 (but £600 - !!). But it seems like pretty much everyone posting about these engines have had problems or disappointments with them. On the other hand, there are now 3.5 hp 4 strokes at about 17-18Kg, and the gas powered Lehr 5hp is claimed to weigh 21Kg. Any thoughts?

[Peter Taylor]

I had a longish chat about the Lehr 5hp on a stand at the Southampton Boat Show which had one on display.  It would appear that it is a little lighter than the equivalent petrol outboard but in most ways very similar. Definitely worth considering for a place where petrol is banned.  Using a propane cartridge the range was rather low (although you could carry spare cartridges). On the other hand if you were using a propane bottle I suppose you could also power a propane heater or stove... so you would only have one type of explosive fuel on board! Propane also gets over the problem of petrol going stale or being contaminated - which appears to be a main cause of outboard problems.  However for power plus range, petrol still seems to have the edge. I didn't do the comparison but I suspect petrol is cheaper too.

I looked at the higher capacity Torqeedo battery.  It looks much like the lower capacity one (!) and, to my mind, has the same problems.  It still results in a usable run time of less than an hour if there is any appreciable wind or current - and you still have what I describe as a "lack of thrust" problem. The BR, BRe and even my BC20 (being epoxy ply) are light boats. When docking in a strong wind "Seatern" blows along "like a leaf on the water" (to quote Matt) and I am grateful for the power of my 6hp Tohatsu to check her speed. The Torqeedo 1003 could not cope in such circumstances (and I really did try to get it to work on Seatern, I really did!). So it's no good for short distances and can't do long ones.

Peter

[Michael Rogers]

I hadn't come across the Lehr propane outboards, so I scurried off to do my homework. Good thinking. And they do a 2.5HP, which would, I think, be something like ideal for my little boat (the Trouper is very light, certainly not more that 100kg all up). And a spare tin of propane stowed away appeals to me much more than smelly petrol tanks/cans. Not to mention the environmental issues.

Apart from finding the money, I go on hesitating for two very personal reasons. First, I'm not sure how to wear an outboard on my boat. The Trouper has an after deck, not the usual free-ish access to the top edge of a transom on which to clip the outboard. The design has a cut-out in the after deck on the starboard side to take an outboard: I hijacked this by moving it to midships and using it (very successfully) for junk-rig sheet purposes. There is a shallowish lip of transom in this cut-out, but even if an engine were secure there I'm pretty sure it would interfere with the sheet. So some sort of bracket on the outside of the transom would probably be needed - which would ruin the lines of my lovely little boat! AND she does not have your bog-standard flat transom: it has a subtle and beautiful curve. I suppose a removable bracket might be feasible. But then, what's the point?

Which brings me to my second reservation - do I really want an engine? I can't think of a situation I've been in where I've thought, 'If only I had an outboard!" I don't think it would have aided my escape from the tide race, for example (see other topics).) Yes I can, actually - on a recent voyage to Wareham and back, an outboard would have been handy on the winding bit of the R Frome. Would it enable me to do things/go places which I don't currently do/go? Possibly. So would it be worth hanging 16kg of (sophisticated) ironmongery on the transom and dragging it round with me? Hmmm...

As I said, personal musings, and probably not of general interest, for which I apologise. Unless someone wants to try to persuade me that an outboard is a Really Good Idea.

So far as electric is concerned (which is sort of where this all started), I've lost interest until The Big Breakthrough (in battery technology) really happens.

Michael

[maxr]

Thanks for the info, Michael and Peter. On the petrol outboard front, does anyone have experience of whether a 3.5hp (which currently appear to be a lot smaller and lighter than the 4/5/6 hp's I've seen) is adequate for an open BayRaider? I guess my worst case conditions in Falmouth would be 6 adults, F6 on the nose, 2 knots of tide, and estuary chop.

[Graham W]

John's BR20 Ella made it safely back to Mylor during a gale this summer with a 2.5hp Suzuki, whereas my BR20 with a Torqeedo 1003 didn't and we had to be rescued by the safety boat.  Personally and in the conditions that you describe, I would want my 6hp Mariner on the back, especially if I wasn't racing.

[david]

I will echo what Graham said above. I also have upgraded my outboard to a 6hp after trying to battle a headwind, tide to get back to port. My Honda 2hp tried its best. (It is a good little engine). But at times, we were at a stand still.  Not wanting to have that experience again, I got the 6hp. 

[maxr]

Thanks all. I just checked, and Mariner 5/6 hp are now down to about 25kgs, not too far off Lehrs's 22kg propane 5hp which is about £200 more. OK, it's anorak time guys ...

Outboard makers appear to quote BHP, not torque. Car manufacturers quote both, and sometimes you find that a low BHP version of the same size engine has equal or more torque, but at lower revs, than the higher BHP version which develops both at higher RPM, depending on the engine control chip programming. Does the same thing happen with outboards, and what matters more with outboards, BHP or torque? Is it possible that say a 5hp outboard fitted with a Saildrive prop might be producing more or less the same propellor pull at lower revs (which might be more appropriate for a BR than say a 10' inflatable) than the 'more powerful' but otherwise almost identical 6hp engine which might only produce its 6hp at the revs appropriate to a planing inflatable??

Leading from that - Saildrive or equivalent versions of outboards appear to be long shaft, when I believe the BR needs what is called both a standard and short shaft (depending on make). Will outboard dealers fit a saildrive prop to a standard/short shaft engine on demand?

Thanks, Max

[Graham W]

Will outboard dealers fit a saildrive prop to a standard/short shaft engine on demand?

I can't answer your technical questions on BHP but Seamark Nunn fitted a saildrive prop to my standard shaft Mariner.  I kept the standard prop as an emergency spare.  The Mariner thus equipped drives the boat at near maximum hull speed at remarkably low revs.  In extensive use in Greece over four weeks this summer, I used less than 10 litres of fuel.

[Andy Dingle]

Max..  I have a Mercury 6 with the high thrust prop, the engine is the same as the Mariner/Tohatsu.

This prop is readily available and easily fitted.

http://www.ronhalemarine.co.uk/superbasket/product/525/Mercury/Mariner_4-6hp_High_Thrust_Prop

A tad pricey if ordered separately, but I got mine as a package with the engine and only paid about £40 for it. As Graham says, the 'standard' prop is then very useful as a spare to keep on board, you would probably want a spare anyway.
Mine is long shaft, but they'll fit just the same on either shaft length.

Even my heavier BC23 is very easily driven with it, even in a sea. My dealer/mechanic did advise that in normal forward use there probably wasn't a huge amount of difference, but he did say I would be very glad of it when (not if!) I ran aground and had to reverse back off a sand/mud bank.  And now, two years later and many groundings, I thank him for that advice. Saved my bacon many times, by just lifting the centre board and rudder (which has usually kicked up anyway), knock her into reverse and back off the putty with a sigh of relief...
I'd definitely go for that option. Money well spent in my opinion.

Hope that helps.

Andy

[Jonathan Stuart]

As other have said, you won't go wrong with a 6hp. Be careful with a 3.5hp because they generally don't have reverse but the legs can be too elongated to allow the motor to turn through 180 degrees in the BR's outboard well. The Honda 2.3hp and Suzuki 2.5hp will rotate freely.

Despite what I said above, I used a Suzuki 2.5hp on my BRe. Loaded with 4 people, ballast and camping gear that will push us along at 4.5 knots in average conditions. Pushing in to a F6 that reduces to 2-3 knots. If I lived somewhere where I might also have to contend with strong foul tides to get back in to harbour, etc, the I'd go for a 6hp, but I love that the Suzuki 2.5 is so small and lightweight and easily handled so I've stuck with that.

[Rob Johnstone]

Vagabond has a 6 hp mercury (aka Freddie) with a "sail drive" prop, fitted at the suggestion of the service agent after the first year. It's now run for about three hundred or more hours, usually starts second pull (unless it's really hot) and pushes us along at 6 kn when pressed. on the other hand, it will give 4kn at about one third revs, consuming about a litre per hour.

BHP and torque always cause confusion. Torque relates to the amount of thrust given out by an engine and power relates to the rate at which it's produced.
When you measure the torque produced by an internal combustion engine as the engine speed inreases, it will increase with engine speed until a certain point is reached (peak torque) and then fall away as the speed is further increased. Peak torque is peak thrust. However, it's not peak power. Given that power is the rate at which the thrust is produced, (eg the energy produced which depends on engine sped and torque) peak power occurs when the increase in engine speed no longer offsets the decrease in torque. Peak power gives you top speed. Peak torque gives you most acceleration.
When driving a car, for max acceleration, you should maintain the engine speed at close to peak torque ( eg change up a gear just after you reach that rev/min). Once you are in top gear, you can still accelerate the car but as the speed increases so do the wind and other resistance forces whilst the thrust by the engine starts to decrease. Top speed is acieved when these forces balance out. (DON'T TRY THIS AT HOME!)

I assume boat props are profiled and pitched  to produce some sort of compromise between high speed and high torque.

[Andy Dingle]

An' Rob should know 'cos he's got an 'ology!

Thanks for that input though Rob, very interesting - sort of explains how/why variable pitch props work too..?

Again. This subject has been, probably quite rightly, raised very regularly as it is an important issue that affects safety and the market is swamped with poor advice from salesmen trying to sell the wrong engine to you.
As an ex owner of a BR20 and a current owner of a BC23 over the past 8 years or so, I still emphatically maintain my position with engines. As others (Graham) have advised, unless you intend to sail on still, flat water - lakes, or very sheltered sea water, then avoid electric outboards. As yet they are just not up to the job, very short range, subject to sea water corrosion and inordinately expensive. (I read recently of an RNLI rescue of a yacht with an electric outboard which had failed, on YBW I think but can'find the link at the moment).

I would also avoid any engine that does not have a proper reverse gear, ie those that spin around to go backwards. Very unreliable if you try to manoeuvre in a crowded marina, anchorage, locks etc and in my opinion they are a recipe for disaster, with the potential for embarrassing apologies to other boat owners with potential insurance claims. They are just not seaman like at all.

You should always have an engine that has sufficient power for every eventuality that may (and will) occur.

Rant over!

[maxr]

Thanks very much all, that's very informative. Sounds like I'd need a Saildrive prop on a 4/5/6 hp motor. Now I'll ask Mr Lehr if such a prop is available for one of his propane outboards.