Trolling Motor

[dee]

I was thinking of getting a trolling motor for my as a backup since its more convenient to have on board. How big of a thrust power should I get to push the boat and is this a better way to go than getting a 5hp.

[Mark Prouty]

I had a deep cycle battery on a small sailboat. I attached a trolling motor to it for power. One evening, I was a several miles out with no wind. The trolling motor ran the charged battery completly down before I could get back. Good thing I had a paddle. It was the wee hours in the morning before I finally reached shore. I'm just glad it was a warm summer night. The stars were beautiful.

I would get the 5hp. IMHO, trolling motors are fine for trolling but not as a backup.

http://www.brokeboats.com/batteries.html

[Chip Hindes]

By trolling motor, do you mean an electric trolling motor?

If so, not sure what's convenient about it for a boat this size.

Even the largest, assuming you can get a propeller designed to push a two ton boat, is going to be good for no more than a couple knots, but only in no headwind and no wave, tidal or current action. You've got to carry along a big honking deep cycle battery which you must ensure is always fully charged and you can't use for other stuff. Even then, if you're far from home you're going to kill the battery before you get there.

Even a small gas outboard will give you way more "thrust" than an electric, and you can run one all day on the gasoline you already have on your boat for the main motor. You still won't make a lot of headway against a current or headwind, but you'll do a lot better than with a troller. You can pull start it even if your batteries are stone dead, and you can add a small alternator which will recharge your batteries and/or power your emergency electronics.

Given, an electric is way cheaper and easier to store and deploy than a small gas outboard. Not enough to make it even marginally useful as a backup, IMO.

Even if you already have a 4-stroke primary motor, consider a 2-stroke as your backup/dinghy motor, and then carry a quart of premix oil so you can mix your own fuel for the motor as needed. Four strokes are quieter, less stinky,and get way better gas mileage, but they weigh a ton and are hard to wrestle around. I know, I bought a 4HP four stroke, and it's all I can do to move it around the boat without dropping it or hurting myself.

[Mark Prouty]

Check my ciphering:

The largest 12V trolling motor I could find drew 50 amps
1hp = 746 watts

How much horsepower:
Convert Watts to Volts:
Voltage = Watts / AMPS
E = P �I
12V = Watts/50 Amps
Watts = 600
1hp/746 watts = HP/600 Watts
Horsepower = 0.8

Trolling motor efficiency := 0.95
Horsepower = 0.95 * 0.8 = 0.76hp

this would be about 3/4 mph.

Yes, but just how long would the best deep cycle battery last drawing 50 amps?

[dee]

Thanks alot for the info. Given the size of the electric trolling motor, it seems easier to store and handle since the does not have that much room for a spare in the transom. Also drilling holes is next to impossible too.

[Moe]

It is quite possible, with all the freeboard of a Mac, and the wind drag of the rigging, that you might not make any headway against a strong current, winds, or wave action, even with a 5 HP outboard, much less a 3/4 horsepower electric motor. And you have sails as backup power.

What's really important is to keep your bow into the seas in the event of main motor failure, and I'm not sure I'd trust either of these little kickers to do even that with a Mac. I'd rather have an anchor down, and quickly.

We take our small Whaler miles out in western Lake Erie in heavy chop, so we need to periodically practice anchor drills, and in those conditions, keep the anchor a lot more handy than in the anchorwell under the bow cushion. Anchor scope isn't a problem in the 30-40' depths. Even though 2:1 may drag anchor, it's often enough to keep the bow seaward (but we have 200' of rode on it anyway... don't want to drag into the limestone littered island shoals).

In water deeper than an anchor is practical, a sea anchor is called for. Personally, I don't really see the need for a kicker on a Mac.

--
Moe

[Duane Dunn, Allegro]

Here is a mod from a guy that installed a trolling motor on an X. He put it on the bow as part of a bow sprit/anchor roller assembly. This might help with an M's limited transom space. He doesn't speak to performance, but perhaps you could email him.

My 6 hp gas motor on my X will move the boat at nearly hull speed. I can't imagine many conditions I would encounter where I would not be able to make good speed with the 6 hp. With ballast full we made 6 knots in our testing. I still need to try it with the ballast empty. It should be even better.

Motors in the 6 hp to 10 hp range have been the standard choice on sailboats bigger and heavier than a mac for years. We are so spoiled by our 50's that we forget what the norm is.

We don't carry the kicker just for the mac. It's main use is on the dinghy, but why not also have it available as a backup for the mac. I think it may also work well on fishing trips as a trolling motor. It's much more economical than my 50 2 smoke at idle.

My only issue with the motor is similar to Chip's. It's darn heavy to manhandle from the transom bracket to the back of the dinghy. I have adapted my aft mount mast carrier to serve as a crane that uses the mainsheet blocks to lift the motor off the bracket, swing outboard, and then lower the motor onto the dinghy transom. This system works great.

One of the cruisers on the San Juan Rendezvous had a round donut dinghy with a electric trolling motor. He zipped around quite well. He didn't seem to have a very large battery system either.