Trolls, Motors, and Other Norse Sagas

[Barnacle Jim]

Good morning,

Trolling motors is what this posting is about. Trolls are always a welcomed topic, too, but trolls you have to watch, watch carefully. They live under bridges and things like that. Trolling motors, I suppose, are a little like that as well. Such motors are often talked about in hushed whispers, and on boats, almost always hidden out of sight.

One manufacturer even offers a vanishing prop. Now, that is a feature which certainly fits the description of a troll. Another manufacturer boasts of a Great White motor. Theses particular motors promise to take a really big bite out of your wallet.

• • What are we talking about?

It's not Billy Goat Gruff exactly. What I would like to talk about has to do with the size of the motor. Like trolls, trolling motors come in a variety of sizes (and maybe shapes as well). There is also a corresponding difference in voltage; the higher the pound thrust, the higher the voltage.

Now, here are the questions. Old Salts (and young, promising salts), Billy Goat Gruffs, and even trolls are all welcome to answer. (Even if you have no idea what you're talking about, you, too, can answer.)

• Questions, Questions, Questions

Is a larger trolling motor necessarily better?

On a boat the size of a Vacationer, what size motor would your recommend?

What difference would 10# thrust actually make? I mean is there a significant difference between 45 lbs thrust and 55 lbs thrust? What about the difference between 55 lbs and 65 lbs thrust?

What about those large trolls, the 75lbs thrust and the 101 lbs thrust? Would these simply be overkill for the type of boat we are building?

(Of course, much depends, I suppose on where we might sail. I, for one, do not intend to sail around the southern tip of South America. I mean look at the movie, Commanders and the Far Side of the World. I don't mind fighting a shark or harpooning a whale or two, but fierce winds are something I would just as soon avoid.) My taste runs more toward the Florida Keys or the Sea of Cortez.

What about voltage? What are the advantages/disadvantages of a 24 volt system?

[Arnie Eaton]

I too would like the same answers to the above questions. I have a 74 lb, 24 volt trolling motor. Have not used it as yet but will in the spring. For pushing a Vacationer, I thought that a big unit would be in order. I also have a small 30 lb unit. Would it be enough to do the job?

[Capn Trey]

I have been using a 54# thrust 12 VDC on my over sized Weekender for three years now and I am happy with my system. Max speed under power is 4 knots, which I can maintain for several hours. In fact I have only had to use the second battery once!

Best of all it don't make all that NOISE, and is environmentally friendly!

I love my electric,

Cap'n Trey

[Pat Mellema]

I have a 36# electric that I have used but had problems as the battery was old. I was at least 4 years old and it wouldnt last. I had enough to get out of the marina but was out of power by the time I got back. If I had a new battery it would probally work fine. I ran accross a 5hp Mariner at a garage sale and bought it for $350. It moves the boat well but is a bit over what the Weekender needs. I liked the electric for its quiet. You feel it as a slight vibration rather then hear it.

[Zeroice]

I have used one of the minnkota 50# thrust motors from last year that could be purchased from walmart and on my weekender it could hold 3.3-3.5 mph (by gps). It worked well out on the ocean and was quite efficient on my 115ah deep cycle. It was nice and quiet and lasted for 2+hours with power to spare. I'm going to try using a 3.5hp gas motor next season and I think I will set it up so I could use the electric as well. It is nice to be able to just drop the motor down and flip a switch.

[Tim Diebert]

I have a 6 hp Johnson on mine. I use it to uproot trees and push powerboats out of my way.

[Tom Holder]

I have a 6 hp Johnson on mine. I use it to uproot trees and push powerboats out of my way.

Are you sure your name isn't Nick Adonodis? Or perhaps you're an Old Relic?

[Tim Diebert]

Good one Tom. It would take a fellow Canuck to be able to come up with that one! Hahaha.

Nope, not Relic or a relic...yet. I just happened to have been dragging this beautiful old Johnson around with me for the last 20 years or so. I love this motor and he currently lives on the stern of my funny little plywood sailboat.

When the wind is down and I don't feel like swimming I do a little Beachcombing, Relic style.

I have heard all the talk about electric/gas/how big/how small....I just happen to be in the far end of this category. Yes, this motor might be 'too big' and too powerful...but I NEVER struggle to get to where I want to get to. I can do hull speed under power in almost any wind (though I sail the bugger when there is wind), depending on the lumpiness of the surface. I have even towed other sailboats to the windy patches. It does not seem to bother my trim much....he sits on the port side, so I tend to pile my junk (gas container etc) on the starboard side.

So if anybody has a six horse and they are a-feared a using it and thinking about buying a smaller one, don't bother...big motors are macho and the girls really dig them.....and hey, you can make some gas money towing jet skis back to the marina.

[Tim Diebert]

Well, Old Beaker....you must not be sailing on our much more Manly and Macho lakes up here in rugged Canada. That little lectrc motor would be shakin in fear if he was to come on round here. And how are you suppose to do any beachcombin with such a thing?

[MikeStevenson]

The minimum I'd use for a Weeknder would be around 36lb. That will move the boat back to the dock fine, but not really have any excess power. 45-55 lb motors are about right, and will get you around even if there's a bit of wind or a litle current. If you have to deal with a lot of wind or current (rivers?), you'll need to move up to a gas motor.

I don't agree with the 18lb = 1 hp. estimate. I'd give it more like 45-55 lb. = 1 hp. This also is more in line with the watt measurements I've taken. When estimating electric motor conversions for wheeled vehicles there is a valid reason to over-estimate the outputs of electric motors. In car use one can use a 20 hp. electric motor to do the work of a 50hp. gas one. This is due to a bunch of little reasons, but in boats and planes it's much less of a sliding scale. You'll get pretty much the work you expect: 1hp. will be the same gas or electric.

One thing which is different for trolling motors as opposed to gas outboards is that as you get moving and the work required to move your boat decreases, you'll find your amp draw dropping quite a bit. This means less power is being used and you can go further. Gas motors tend to use a more linear amount of fuel and don't automatically conserve power as well as electrics (cars, boats, etc.)

24v. motors will have the stated advantages above, but also have a bit more reserve power than the 12v. versions. Not usually needed, but there. The big problem with all trolling motors is the prop: They're pitched too slowly (as trolling does want to go slowly.) You'll top out at 4 to 4.5 and nothing will really help this. A big advantge of this, and why we don't go to the trouble of changing props, is that that's nearly as fast as you can expect to go and plenty fast enough to get around. As you reach this speed, the prop will "unload" (reach a point where it's not working as hard) and the power use will drop and so we leave things pretty much alone prop-wise.

See the E-motor page for more.

http://www.stevproj.com/EMotorIdeas.html

Mike

[Joel]

I was also wondering how HP related to # Thrust. I did see 16# = 1HP in Larry Browns book "frugal Yachting".

I found this formula for Direct Current motors in a electrical reference book I have. Volts x Amps x efficiency/ 746 = 1HP . Based on the Current draw Minkota shows for various models on their web site, not even the largest motor produce 1HP.

But then again..... I've noticed a lot of shop vacs with motors rated at 5 or 6 HP, yet they draw less than 15 amps at 120VAC.

"What does it all mean?"

joel

[MikeStevenson]

Joel:

As you noted, 746 Watts is a Horsepower. Your book's formula includes an efficiency adjustment, which is probably fairly useful to add. Watts and Horsepower are units of work, so technically they shouldn't be adjusted with a variable for efficiency

[Joel]

Mike , I checked the printed Catalog I have at home. The 100# thrust motor is actually 36 volts it draws 37 amps max. that come out to about 1.8HP. The largest 24 volt motor is 74#, it draws 45 amps max. about 1.45HP.

There is a huge price difference between the standard and saltwater versions. have you had corrosion problems with the motors you have used?

joel

[MikeStevenson]

Well, I'm afraid I stand by my previous post of around 50lbs. or so to do the work of a 1hp. gas motor. There well may be a scale effect in play also (bigger installations tending to use smaller electric motors, comparitively.)

I haven't done a change-out of a larger inboard installation, only several smaller electric boats. We may not be comparing the same fruit in practice.

Mike

[MikeStevenson]

Very true about the differences in e-Hp. vs. IC-Hp.

It would be fun to do some tests on a little larger machine. Also to do some prop design test.

One of these days.

Mike

[Sailor3356]

My friend Pat and I went out the first time on his Weekender. It was an hour before sundown and it was the first time the boat had ever been in the water. We motored out with the aid of a quite electric motor. Slowly we went from the marine to the lake. The boat road like it was a production model. We set sail and worked our way out toward the point. With very little wind the boat mostly moved by the electric motor. As the sun started on its downward path we turned the boat around and started heading back. Being a new boat one of the things not yet installed was the running lights. Still a mile out the motor started to slow down. This was not a good sign. :roll: As the sun set the breeze was slowly coming up and the sails started to pull the boat along. The wind had shifted to the North, right from the direction we need to go. The breeze was not strong, but we where moving. We watched as a sheriff

[Barnacle Jim]

I received a posting from a genuine troll on the very topic we are discussing. You may ask why the troll did not post the answer himself. I must tell you that trolls are not usually good with computers. Besides, a troll, at times, can be rather shy.

The troll, however, did send me a picture of his home, saying there might be excellent sailing in such a region, and that I should consider launching my boat in such a place.

"Just in case, you may think that we have little or no wind in the land of the trolls, here is another picture," said the troll, rather reassuringly.

Apparently, the troll did not believe that we would believe him. Trolls, as you know, are notorious for exaggeration. This next photograph, however, caused me to change my mind a bit. "Maybe this troll would know something about sailing," I thought to myself.

"But you trolls live under bridges and things," I said. "Everyone has read Billy Goat Gruff."

"Some trolls do," he admitted. And then, he continued, "Bridges are close to water, you know, so I could say something about boats."

He did have a point. I hesitated, but almost asked him about trolling motors and voltage. Instead, just to be polite I asked him where he lived. "Oh, I live in a house much like yours," he said.

Well, the house did look a lot like mine, but the roof seemed more like my backyard than anything else. By now, we had become good friends, and he offered me a photograph of himself.

(Now, you must know when a troll offers you a photograph of himself, it is genuine friendship. Most people never get to see a troll during their whole lifetime.)

"But what about trolling motors? " I asked. "And things like that?"

"Well, what everyone has said about trolling motors on this site is quite accurate," he said. "Trolling motors have to be good. After all, the motor is named after trolls like myself. You can have confidence in them."

I smiled at his comments and thought about sail boats, the ones that we build. These boats take us into many places and into many adventures. There is a wonder about a sail boat, a wonder about the quiet of the wind, and the rippling sound of the water. You might say there is something almost troll-like and magical about sailing, something very wonderous indeed.

[Konrad in Lincoln]

I originally had a 52lb thrust electric for my Vacationer, and I felt that it was woefully underpowered. It didn't have the authority to maneuver the boat during docking situations, if there was lateral windage.

I eventually bought a Murcury 2.5 hp outboard, and it's the cat's ass. WAY stronger than that 52 lb electric could have ever hoped to be. And it rotates 360 degrees for some deft boat control.

Just my never-to-be-humble opinion.

[thebob]

It is very difficult to compare the HP figure given for an IC engine with the "thrust" that electric motors are rated in.

Although you can convert HP into KW, this really does not help us in the real world because of the fundamental differences between the motors and the terms themselves.

Measuring the amount of watts an electric motor consumes would be as useless as measuring the energy in the gas an ic burns.

You must remember that HP = TORQUE x RPM