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Folks,

Planning on using a 6 hp Tohatsu 4 stroke on an 18 foot Sotar raft on a VERY long Yukon River trip. New outboard broken in last summer and running great. Got the factory repair manual and am putting together a maintenance parts list to include spare water pump. I have little experience with a small outboards on the silty Yukon and am trying to decide if having adequate spare parts will suffice - or do I need to actually take a spare motor (or have one ready to ship to a village along the way as a replacement). I just have no idea how reliable a water cooled 4 stroke will be in this kind of silty water. I do plan on changing oil and drive shaft fluids during the trip and will have provisions for flushing the water pump system. The raft is outfitted with an excellent rowing set-up, but I believe the motor will be "required" to combat the constant up-river winds for the long trip so I consider the motor very important to complete the trip. Any advise/suggestions would be most appreciated. Thanks.
 

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I have used my 6hp Nissan to push 5 rafts out of The Grand twice. I don't think you will have any problem. How many hrs of running will the motor get? 50 hrs is ok for the oil. Even at 5mph that's a lot of river miles. Unless you use it for a rototiller the silt won't be a problem. The 3gal tank had over a gallon left after 60 miles if that helps.
 

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The silty water won't be a big problem. The extra impeller/water pump is a great idea though..your oil should be good for the entire trip, change it after when you clean/flush the motor.

My best advice is to read the water carefully, even flat water. Gravel/cobbles bars will wreck a prop or lower end. Always pay attention. Sand bars and running in mud will ruin the water pump. Read the river, little glassy areas, upwellings, and breaks in the surface chop will reveal shallow areas.

Have fun man!
 

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By the way I run silty water and swamps in my fiberglass boat with a 8 hp kicker motor and a 50 hp mercury. Boat motors, especially two stroke are made to be low maintenance. Stay out of shallows, and kill the motor near shore.
 

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You are FAR more likely to need spare prop (s), cotter pins and a prop wrench. "Twatzoo" makes a great engine- you chose well

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Tohatsu on the Green and Colorado

Couple spare impellers and a spare prop nut and pins.
Couple spare props.
Carb rebuild kit.
Couple fuel filters.

Impeller has lasted from purchase to present time, 5 years, 8-900 miles of silty river operation.
Props last a long time at low throttle operation. Bring a file.
Crap in fuel, sandstorms, storm fronts moving through, eventually carbs clog and will not run slow or idle. Two rebuilds for me in same time period mentioned above. Bring something to poke out the jet with. Small-stranded wire.
Good Luck!
 

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Check with this outfit

The Boat Shop in Fairbanks. Good folks that I'm sure can give you good advice on running an outboard on the Yukon.

+1 on whatever you'd need for running a prop into a gravel or sand bar - AK silty rivers can be VERY hard to read and the gravel bars are always changing.

Boat Shop, Inc. Fairbanks, Alaska
 

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Never used the motor you are referring too, but I have run a plethora of motors on silty rivers ranging from 4-stroke 10hp's to 2-stroke 30hp yamaha's and beyond. To the guy's saying bring a 2nd prop I agree 100%. When I was running motors frequently I always had my "beater" prop, which I used when the going was sketchy as in rapids, shallow water, and also a prop that I only ran when I wasn't worried about hitting stuff such as a deep channel where I was going to be running the motor at 50-75% cob for an extended period of time. If you do nail a rock or tree or gravel bar even just one bent prop-fin will cause vibrations that will destroy the motor. I always carried a hammer, and a file and have many times resorted to amateur prop repair on the river in a last ditch effort to get to the take out by filing and pounding the prop back into a workable shape. Also, I always carried a length of bailing wire, and paperclips in case the water pump tubes got plugged up with gunk. Something to think about... Also breaking a pull cord is a pain and I carried a spare recoil assembly. One thing that I took for granted until I didn't have it was a quick release on the lock mechanism so that I could pull the motor out of the water quickly. I found when the motor could be pulled out freely without having to pull a pin and whatnot, was that when a motor does hit a rock it simply slides over the top of it, not receiving as much damage.
 

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Get a good prop guard like the one below. I have one on the same motor you have. It requires some slight mods but they are easy.

Rock Hopper Motor Guard : Cabela's
That prop guard looks awesome, paired with a motor that doesn't lock into the down position that thing would basically let the motor slide over rocks, logs, etc. and even keep it out of the mud and gravel bars.
 

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Never used the motor you are referring too Mercury & Nissan are built by Tahatsu at least the small engines,maybe a lot of others too. Yamaha builds there own. If I was to buy another 6hp I would spend the extra $500 to get a Yamaha. 2 cylinders make it run so much smoother
 

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Mercury & Nissan are built by Tahatsu at least the small engines,maybe a lot of others too. Yamaha builds there own. If I was to buy another 6hp I would spend the extra $500 to get a Yamaha. 2 cylinders make it run so much smoother
Good to know! The last trip down Cataract that we took a motor on we used a 10 hp (i think) 4 stroke mercury. The motor has been well cared for throughout its life with regular maintenance and whatnot however we encountered many problems with it. I was not a fan of it... Having mostly used 2-stroke motors from a ease of use standpoint I find them much more reliable, easy to deal with
 

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Hi,

I've uneventfully run Honda, Nissan, and Tohatsu outboards on my rafts -- ranging from 5 to 18 HP in size, all four stroke. My Honda five ran for 7-8 years in numerous silty trips with no noticeable loss in output pressure. I'd guess it had a thousand miles on it's impeller before I changed it as a precaution.

It's worth noting that fuel mix is a huge issue with these relatively small engines, and could be a possible explanation for some problems people have with them.

The addition of ethanol to gasoline -- and continued ethanol exposure while the fuel mix is in tanks, carburetor bowls, and hoses -- can cause deterioration of some seals and gaskets. And of course, any gas left in a carb over time will be subject to gumming, which creates a different kind of performance problem.

Whenever possible, I try to fuel my outboards with pure gas just before a trip, and put Stabil in my tanks as well. That helps avoid those kind of problems, which some folks say can crop up after as little as 30 days after the mix is put in a tank and left to sit there.

FWIW.

Rich Phillips
 

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Hi,

Fuel mix is a huge issue with these relatively small engines, and could be a possible explanation for some problems people have with them.

The addition of ethanol to most gasoline -- and continued ethanol exposure while the fuel mix is in tanks, carburetor bowls, and hoses -- can cause deterioration of some seals and gaskets. And of course, any gas left in a carb over time will be subject to gumming, which creates a different kind of performance problem.

Whenever possible, I try to fuel my outboards with pure gas just before a trip, and put Stabil in my tanks as well. That helps avoid those kind of problems, which some folks say can crop up after as little as 30 days after the mix is put in a tank and left to sit there.

FWIW.

Rich Phillips
Rich, are you saying that you run a stabil/gas/ every time you use your motor?
 

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Hi utrafter,

It may seem like overkill, but I put Stabil in my storage containers if there is any chance at all that the fuel won't be used in the next few weeks -- even for my home power equipment. Living in Midwest corn country, it's really hard to find fuel that isn't ethanol-infused. I sort of have to live with it. That's my preventive strategy, and I've never had a gumming or seal/gasket failure like a lot of folks seem to have.

Also when the motors are going to sit for a while and still have fuel in the lines (and bowl in the carbureted ones), then I run some fuel with Stabil through them. That's for the same ethanol-related reason, plus to prevent the more common gumming problem on jets and other internal parts. For example, I put Stabil in my snowblower tank at the end of the season, run it long enough to be sure it's hit the carb, and then put it away. It sits there for 7-8 months and inevitably starts right up.

When I'm doing the Grand or some other Western river trips with a motor, I try to stop somewhere closer (in Page for GC trips) and get pure gas. Regular Lake Powell boaters talk a lot about using non-alcohol fuel mixes because of the potential problems it creates for them -- particularly if the motors are older or if their fuel tanks have anything resembling fiberglass in them. And I also find I get better fuel economy with the pure fuels than with the "E" blends.

FWIW.

Rich Phillip
 

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I have a 6hp Tothatsu and have found that switching to the high thrust prop made quite a bit of difference pushing a bunch of fully loaded rafts out on Cataract and below Diamond on the Grand Canyon. The stock prop that comes on the normal model of this motor is designed for higher speed dingy use. The "pusher" prop used on the sail pro model of this motor is intended for heavier loads when used as a kicker motor on sailboats. I keep the stock prop as my spare.
 

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RichP and Dsrtat identified the two most serious issues I've ever had with motors, bad fuel and, though not critical, having a high thrust prop definitely helps. The Sail Pro you have comes with the high thrust prop so you have that covered. I only run premium in small motors to get the highest octane I can. Haven't tried Stabil but I run mine dry and loosen the drain screw on the carb when storing them. Other than that having a spare spark plug, impeller and gasket kit won't hurt and of course some tools. Most of my motors have run well so long as I don't crash them into a rock and break something, which has happened. Gravel bars and sand have not caused any serious problems over time so long as you have the prop guard.
 
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