Motor on 18 foot raft - self bailer - Mountain Buzz

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Old 02-08-2013   #1
Yukon, Alabama
Join Date: Jan 2013
Posts: 92
Motor on 18 foot raft - self bailer


Contemplating putting a 10 hp 4 stroke outboard on an 18 foot Sotar self-bailing urethane raft with 24 inch tubes. Total weight in the boat will be about 1,900 pounds which is well below it rated capacity.

I am planning on using a 10 h.p. 4 stroke motor to help with the slow spots and to battle the wind. Not expecting any speed

ISSUE: I've heard from some folks that that they have experienced a couple inches of water pooling in the stern when motoring with a self-bailer - water coming up through the bailing holes as the stern dips down under power. I've hear from others that this won't be an issue with the 18 foot Sotar.

QUESTION: Looking for any first hand knowledge on this issue of stern dipping down and taking on water through bailing holes when using a motor - particularly with an 18 foot Sotar raft.

Many thanks for any and all comments.

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Old 02-09-2013   #2
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Join Date: Oct 2003
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I dont know about an 18' sotar specifically but i would think there would be a little water in the stern of any raft with a motor running. Definitely was on any raft i have ever motored, even the 22' snout would get water sloshing around on the back floor. The force of the motor draws the back of the raft down. Every boat sinks the ass when it is under way, makes me think of miami vice.

I have a raised floor in the back that my gas tank, motor kit, fire extinguisher, etc. sit on. The water splashes around under the floor. I sit on a platform above the floor that spans the tubes. It makes a nice place to sit, gets me away from the motor a little bit and gives me a place to stand up high real quick to have a look or just stand and motor for a change of positioning on long days.
zach baird
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Old 02-09-2013   #3
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Westminster, Colorado
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Have a 9.8 mounted on 18' floor boat, so only comment I have is gear distribution in front needs attention so boat rides level in the water. And yes, beats rowing against afternoon up river winds!
"If you understand, things are just as they are; if you do not understand, things are just as they are."
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Old 02-11-2013   #4
La Grande, Oregon
Paddling Since: 1984
Join Date: Dec 2011
Posts: 107
plenty of motor

We float the lower salmon/snake every year we don't secure a permit on the main or middle fork of the salmon, like last year. The snake below the salmon is like a great big pond with a up stream wind. We take a motor, tie several boats together and motor out. I have a 15' Hysides, with a motor mount in the very back. I am sure there is water in the self-bailing floor, as by the time all the gear, the motor and me are back there, there would be water anyway. We use a 7 horse Honda, also a 4 stroke. It works it a little, but we run it about 6 hours, maybe 4 gallons of gas, and it works great. usually have 3-4 other boats tied to the one. I sometimes have problems with cavitation, if I don't get the motor low enough in the water, or try to go faster than it can push, but it sure beats the wind blowing us upstream! We have used the motor probably 6 times. will NOT go without it on that streatch.
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Old 02-11-2013   #5
codycleve's Avatar
salmon, Idaho
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Once you drop the motor is it required that tou have your boat licensed and have a fire exstinguisher...
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Old 02-11-2013   #6
Searching for water....., Idaho
Join Date: Apr 2012
Posts: 187
I think that on most waters you need to register your boat if it is motorized. I know for sure that on the Lower Salmon the boat has to be if it is motorized.
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Old 02-11-2013   #7
whoville, Utah
Paddling Since: 1988
Join Date: Feb 2013
Posts: 12
raft w/outboard

We run rafts with outboards. We are getting lazy in our old age- grand, cataract, westwater, deso, etc., just for the flat water.
Motor size of choice is 8HP (best overall gas economy and speed), but depends if you are pushing/dragging along other rafts.

Yes, where will be water in the stern of any raft pushing with an outboard.
I've got a NRS 18' & Marvia 16', my buddy has a 18' sotar, pushing with a 8hp merc.

Only issue is if river is dirty from recent rains, it'll leave a scum ring around raft and dry bags.

Trick is finding a really good transom mount thats bomber.
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Old 02-11-2013   #8
whoville, Utah
Paddling Since: 1988
Join Date: Feb 2013
Posts: 12
If you are using an Outboard on your raft, it must be a four stroke on all NPS, BLM & USNF rivers. ALL western states require the raft or motor (depends on state) to be registered. You must provide annual registration paperwork, placards w/ decals (for bow both sides), fire extingisher, throw cushion (coast guard requirements), spare paddle (or oar), and lights (if rafting at night- don't laugh we have had to do this in an emergency).

At put-in, you will be checked for all of these items by the river ranger. You may also be checked on the river by river rangers (happens routinely).
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Old 02-11-2013   #9
The Mogur's Avatar
Oregon City, Oregon
Paddling Since: 1972
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Originally Posted by Yukon77 View Post
Contemplating putting a 10 hp 4 stroke outboard on an 18 foot Sotar.
That seems like overkill--and a heck of a heavy motor. We used a 6 hp single-cylinder Nissan (about half the weight of a 10HP Honda) to push five rafts down to South Cove. We didn't have a headwind, but we ran the engine at barely over idle speed most of the way.

The extra horsepower won't make you go much faster, because the hull speed of an inflatable raft (or in our case, a cluster of rafts) is pretty slow--hull speed being the maximum speed a given boat can be moved through the water regardless of power. All the extra horsepower will do is cause cavitation and whip the water into a froth.

On our next trip, we're going to take a lightweight Honda 2HP motor, which weight under 30 lbs. Yes, it is a 4-stroke.
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Old 02-14-2013   #10
Yukon, Alabama
Join Date: Jan 2013
Posts: 92
Good information. I sincerely appreciate you folks taking the time to share your knowledge.
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