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Old 08-07-2013   #1
 
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Telluride, CO, Colorado
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Motor questions

I have very little experience with motors and after searching existing threads I still have some questions on what size of motor will push how many rafts. I am trying to plan for an upcoming trip that has lots of flat water.

Obviously the boat size and amount of gear/people loaded into it will affect how effective the motor is. For the sake of this question lets say the main goal is to get multiple boats through flat water.

From what I can gather the 15hp motors are typical for 18 foot boats on the grand, how many other boats could this one motor push and still be worth the gas its burning and not crush the motor? From here you step down in both horsepower of motor and size of raft but what are typical motor sizes for a 16 foot or 14 foot boat and how many other rafts can these push?

Another side thought is what formation is the most effective? Long, snake style seems like a good idea but may not work well in reality. it seems like a diamond shape may be best for moving multiple boats with one motor.

thanks for your input buzzards, your always there for me when I need you.

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Old 08-07-2013   #2
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New Castle, Colorado
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Thanks for posting this. I was just on a Westwater trip that had a boat with motor. We lashed 5 rafts together and kept moving at 4 - 5 mph against the wind and the motor was very quiet (not opened full bore?). I was told it was a two-cycle- doesn't put oil in the river- and it said 5 hp. on it. I looked up similar models and nothing claimed to be able to achieve the same results.
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Old 08-08-2013   #3
 
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Hi,

I've used a Honda five for years, pushing as many as four other boats, on Westwater, below Cat, and on the bottom end of the Grand. If all you're looking to do is keep moving at a modest pace against all but the most ferocious wind, a five is fine. I'll be taking that motor again this fall to push out on the Grand after Separation, on a three boat trip.

For comparison, the big rigs on the Grand use 30 hp four strokes. When I've motored the Grand in my 20 foot cat, I've used an 18 four stroke. But those are full trips requiring lots of maneuvering power in rapids, not push-outs on flat water.

Lash them frame to frame in as compact a formation as you can -- something that will be determined by how many rafts/cats you have, and how big each boat is. I've never towed a line because I think you lose a lot in control. But it might work if you were on a real wide stream/lake, and could be sure the tow line didn't foul the prop. However, I still believe the lash-together method is better, and it allows a lot of fun social interaction.

Finally, check the river regulations on whether two strokes are permitted. Four strokes are increasingly required in places like the Grand.

FWIW.

Rich Phillips
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Old 08-08-2013   #4
 
East of the Pine beatle, Colorado
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Quote:
Originally Posted by Gremlin View Post
Thanks for posting this. I was just on a Westwater trip that had a boat with motor. We lashed 5 rafts together and kept moving at 4 - 5 mph against the wind and the motor was very quiet (not opened full bore?). I was told it was a two-cycle- doesn't put oil in the river- and it said 5 hp. on it. I looked up similar models and nothing claimed to be able to achieve the same results.

2 stroke (or 2 cycle- same thing) uses a gas/oil mixture in the tank and that burned oil does end up in the river and in the air. They're simple, reliable and give a lot of power for the size/weight... but the oil issue is making them increasingly obsolete. 4 strokes have an oil tank just like your car- and the oil and gas never mix. You change the oil every so often and it just burns regular gas in the tank. They're MUCH quieter, cleaner and less powerful/torquey for a given displacement than a 2 stroke.... so they've got to be bigger and heavier to reach the same HP as a 2 stroke. Some rivers are banning 2 strokes, so be sure of what you are buying and where you intend to use it. Older small outboards are almost universally going to be 2 strokes... so watch those Ebay ads and be certain you know what you're buying. At around 6 HP you're going to start seeing a separate gas tank for the motor- beneath that threshold you will usually see the gas tank built into the top of the outboard. Once you get to that large a size, you're looking at a dedicated fuel tank and a hose to store and place on your boat.

I'd go for about a 4 or 5 HP 4 stroke for push-out duty on a small raft flotilla. That tank on top of a 4 stroke would get you out of any day trip row-out (westwater) without having to take along extra gas. A 15 HP outboard is a pretty big motor for these sorts of things- made more for a small fishing boat on a lake- on plane and going 25 mph or so. Way more power than you need for a slow push on a raft flotilla.... and heavier and thirstier every time you want to use it.
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Old 08-08-2013   #5
 
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Telluride, CO, Colorado
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Thanks for the info everyone. Keep it coming!
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Old 08-08-2013   #6
 
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electric

Saw a guy on the Upper C that had an electric trolling motor hooked up to a car battery. Not sure what size, but he said it worked great and was only a couple hundred bucks. Anyone use one of those?
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Old 08-08-2013   #7
 
SLC, Utah
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I have an 8hp yamaha 4 stroke for my 18' cat. It's much quieter than any 2 stroke out there. I've pushed 6 rafts out of westwater easily in the 5 to 6 mph range. On cataract with 3 rafts we were doing 8 to 10 mph (even with some wind). The prop you use will make a lot of difference as well. I have an oversized prop that pushes some serious water.

Lash up frame to frame, never use D-rings or boat handles since there is a fair amount of force generated when all tied up. From what I've tried: 4 boats = diamond pattern, 3 boats = 1 on each side of the motor boat, 5+ boats = just start strapping together because that is just a lot of rubber to be pushing.

Now if I could only get on a Grand trip, I'd be happy to report how well the motor did there (fingers still crossed for lottery success).
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Old 08-08-2013   #8
 
La Grande, Oregon
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motor

We have used a motor many times for lower Salmon-Snake river. Much flat water and lots of up stream wind. We used a 7.5 Honda and an 11hp Yamaha, both 4 stroke. not a lot of difference. About 5-7mph is all you can expect to get, afterthat that boats push much harder, causing a lot of stress on the tie-together points. We use short pieces of rope with carbiners, so that we can quickly disconnect, but that is due to the placement of rapids about every 3 miles in the last 15 or so, so we have to unhook through them. Note that sometimes it is easier for the outside boat to stear using an oar, than it is for the person controlling the motor.
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Old 08-08-2013   #9
 
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Single file

During heavy wind and waves we usually switch to single file.
The motor cat in the front cuts the wind and waves and there is less splash/spray.
Rig each boat with a simple front and back bridal loop tied to both sides of the frame then clip boats together for fast disconnect.
Realize that additional boats behind will really increase the strain on the first rigs.
In a pinch after second motor failure we have rigged 6 boats with one 9.8 merc and still made decent progress with the front cat "jumping" whitecaps.
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Old 08-08-2013   #10
 
East of the Pine beatle, Colorado
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Quote:
Originally Posted by glax View Post
Saw a guy on the Upper C that had an electric trolling motor hooked up to a car battery. Not sure what size, but he said it worked great and was only a couple hundred bucks. Anyone use one of those?

Whole different ball game. Trolling motors measure their "thrust" in Lbs... rather than HP. You'll find that for one boat, with no wind- it'll work for a while. Nothing matches the efficiency of a gas powered engine. Not even close. I've had several trolling motor rigs on saltwater fishing boats- and while they're invaluable in certain situations, their forte is silent, slow and minimal current. Not the design you'd want for moving multiple rafts-
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