Electric back-up motor

[SiggiJo]

I was going to get a 4-5 hp JohnnyRude kicker as a back-up motor for my 14´ boat.<br /><br />Since I´m also thinking about going for two 88Ah AGM Deep Cycle batteries, I´m going to have a bit of electrical power in reserve for this size boat, so to save weight and space, I have been looking at electric trolling motors.<br /><br />I have been reading up on trolling motors in this forum and elsewhere, and I am still unsure if this would be suitable and be able to push me home in case my main motor failed.<br /><br />Trolling motors are in lbs and gas motors in hp and no simple formula to compare. Would this work and if so, what is the most powerful 12V motor your would recommend? <br />Also, since I would mount it on a transom bracket I have already bought, can the shaft be made shorter - i.e. does the top or the bottom units unbolt from the shaft, so it could be made shorter without too much surgery?<br /><br />Or - exepcting winds, current and tides, should I just stick with orginal idea of the conventional 3-5 hp outboard and maybe just go with one boat battery? <br />I have a "large" 14-footer with good freeboard for her size, so I think carrying capacity would be ok for either gas or electric, but the idea of smaller size and no/low maintenance (except for battery) is interesting - but at the end of the day, it´ll have to get me home if needed...

 

[Paul Moir]

Re: Electric back-up motor

I would not put far to sea with a trolling motor for backup. If bad weather is an issue, the trolling motor (pretty well no matter what size) is going to be useless.<br /><br />Thrust is highly dependant on the propeller itself, and how fast the boat is moving. Trolling motor makers control the propeller so they can say something about the thrust. I guess they measure it without 0 forward motion. But I think that pretty well the largest TM you can get is about 2hp. <br /><br />Personally, I think the 10% rule for a kicker is a good one. That is to say, something that is about 10% the power of your main motor. But naturally it all depends on what you can reasonably expect to be boating in. If you're just noodling around a small lake on sunny days, a pair of stout oars could suffice. If you're going out of sight of land in the North Sea, a trolling motor (of any size) will not do.

 

[rickdb1boat]

Re: Electric back-up motor

If you are talking miles to get home, then opt for the gas motor. If your on a local lake setting with help nearby, then a troller might work out fine in a pinch. I would get the most powerful one your wallet can handle. They come in different length shafts, too. What type of boat are we talking? Fiberglass or Alumnimum?

 

[SiggiJo]

Re: Electric back-up motor

My boating is going to be mostly done on the English Channel - which sort of is a part of the North Sea. Due to my boat size, I will be limiting it to sunny days and calm seas though.<br /><br />My boat is fiberglass, but will probably be a bit on the heavy side for her size due to engine being a 70 HP Rude and a fair bit of equipment onboard.<br /><br />I have also been considering buying a 4 HP two-cyl older JohhnyRude or a newer Tohatsu/Nissan 5HP as a back up - which one would you go for if we discount electrical back-up power - which is what I think we are doing?

 

[rickdb1boat]

Re: Electric back-up motor

For my money, just as a back-up, I don't see how you could beat an older reliable JohhnyRude that's in good shape. But then again, I'm really partial to them... And yes, we have discounted the electric troller for the Channel...

 

[Paul Moir]

Re: Electric back-up motor

I think you're choosing between two of the very best. Like Rick I'm very partial to Johnny/Rudes, but if that's a '70s era 4hp I don't really think it's going to be enough to push you around. Personally, I think the 4hp label on them is just a little generous. The later (80s-) revamped 4hp would be fine though.<br />If you plan to use it a lot I think you'll find the 2 cylinder J/E a lot less buzzy than the 1 cyl Nissan. But they're both great outboards.

 

[deerhound]

Re: Electric back-up motor

Hello again SijjoJ, I did after consulting this forum buy a 1990 Evinrude 4hp twin as back-up for my speedboat, I tested it out on a inflatable, although I was unsure as it is a long shaft I was amazed at the performance and how it pushed 3 of us along no bother, I am sure it will be enough as back-up,the problem we both have is size of our boats for the sea,(almost calm conditions) I am about to buy inflatable to pull untill I gain some confidence in bigger engine,I have two of everything, I think I'm paranoid but when I see how low she sits in water HMMMMM! well,did you watch rescue on UK TV on speedboats? frightening stuff! JBD

 

[ed/il]

Re: Electric back-up motor

Find a friend with a boat. Keep an eye on each other untill you trust your boat.