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Thread: Outboard Motor Review

  1. #1
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    Default Outboard Motor Review

    Gents,

    This is my first post on this forum however I've been reading reviews for quite a while and have benefited greatly from other users opinions and know how. One piece of information that I've had a hard time running down is what size outboard to put on my 15' self bailing raft (nrs otter). After much research looking at 3.5hp, 5hp and 6hp motors, I ended up buying a 3.5hp Tohatsu long shaft from Storm Chasers Marine down in Seward. At my request, they graciously changed out the stock 7" pitch prop with a 4.5" Pitch, heavy load prop. I took the raft out to Sand Lake this afternoon and was quite impressed with the little motor's performance. With four adults, the frame and about 100lbs of gear onboard, my gps clocked us doing ~3.5 mph at ~15% throttle, just slightly above idle and quiet enough for you to hold a normal conversation. At ~30% throttle, the otter was moving along at ~5.0 mph. At ~60% throttle we were only doing ~5.5mph. The torque of the motor was pulling the back of the raft down roughly 4 inches and we had about 5" of water in the back of the boat coming through the self bailing holes. After seeing this, i believe that any additional horsepower couldn't be utilize with the self bailer. In fact, I wouldn't be surprised if a 2.5hp outboard with the appropriate prop could push the raft at 5+ mph.

  2. #2
    webmaster Michael Strahan's Avatar
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    Excellent first post, and thanks!

    Your experiences echo mine with self-bailers, and it gets even worse with a larger load, in terms of water migrating up over the floor in the stern. I think you hit the sweet spot in terms of horsepower, and I agree with your conclusion that a smaller outboard would probably do as well.

    Thanks for posting this! Lotsa folks out there wanting to increase their drift speed on longer floats, or perhaps even to navigate a lake.

    -Mike
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  3. #3

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    I too have the 3.5hp kicker on my 16foot cataraft. I have been wanting to know how a 5hp and a 9.9hp engine would perform on it but haven't had the opportunity. I have the stock prop on it now which must be the 7" pitch? What brand did you buy? I have a Tohatsu. Great little engine, quite, light but burned more gas then I imagined.

    Quote Originally Posted by texinak622 View Post
    Gents,

    This is my first post on this forum however I've been reading reviews for quite a while and have benefited greatly from other users opinions and know how. One piece of information that I've had a hard time running down is what size outboard to put on my 15' self bailing raft (nrs otter). After much research looking at 3.5hp, 5hp and 6hp motors, I ended up buying a 3.5hp Tohatsu long shaft from Storm Chasers Marine down in Seward. At my request, they graciously changed out the stock 7" pitch prop with a 4.5" Pitch, heavy load prop. I took the raft out to Sand Lake this afternoon and was quite impressed with the little motor's performance. With four adults, the frame and about 100lbs of gear onboard, my gps clocked us doing ~3.5 mph at ~15% throttle, just slightly above idle and quiet enough for you to hold a normal conversation. At ~30% throttle, the otter was moving along at ~5.0 mph. At ~60% throttle we were only doing ~5.5mph. The torque of the motor was pulling the back of the raft down roughly 4 inches and we had about 5" of water in the back of the boat coming through the self bailing holes. After seeing this, i believe that any additional horsepower couldn't be utilize with the self bailer. In fact, I wouldn't be surprised if a 2.5hp outboard with the appropriate prop could push the raft at 5+ mph.

  4. #4
    Member Birdstrike's Avatar
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    Thank you texinak 622. I too have a 15' Otter and have been toying with the idea of adding a kicker to help with some lake crossings. Your info helps tremendously.

  5. #5
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    MTfisher, my outboard is a 3.5hp 4-stroke Tohatsu as well. The stock prop on the 3.5hp Tohatsu is the 7" Pitch, but you can swap it out to the heavy load 4.5" pitch prop for about 35 buck. If your gross weight is heavier than 1,000lbs, it might be worth testing out the slow pitch prop before dropping another 1,500 bucks on a bigger motor. Your cataraft probably has significantly less drag than my self bailer and might benefit more from the additional horsepower. I'm surprised to hear that your full burn is that high. I motored around for almost 2hrs on less than a tank (1/3 gal) of gas, but I kept it under 1/3rd throttle for most of the time.

    http://www.tohatsu.com/accessories/prop.asp

  6. #6

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    I purchased a different prop, the moderate load prop which is the 5.7 pitch prop. It pushed the boat much better while we had 3 people a dog and camping and fishing gear. Seemed like I could run 1/2 to 3/4 throttle and it was using the hp much better. The nice thing with the props is they are light so we can bring a few for different conditions. I may pick up the 4.5 pitch and see what that does. That way I will have all 3 props. Fuel burn was still high. We motored across skilak and down the middle this weekend. Wish they had an external tank hook up.

    Quote Originally Posted by texinak622 View Post
    MTfisher, my outboard is a 3.5hp 4-stroke Tohatsu as well. The stock prop on the 3.5hp Tohatsu is the 7" Pitch, but you can swap it out to the heavy load 4.5" pitch prop for about 35 buck. If your gross weight is heavier than 1,000lbs, it might be worth testing out the slow pitch prop before dropping another 1,500 bucks on a bigger motor. Your cataraft probably has significantly less drag than my self bailer and might benefit more from the additional horsepower. I'm surprised to hear that your full burn is that high. I motored around for almost 2hrs on less than a tank (1/3 gal) of gas, but I kept it under 1/3rd throttle for most of the time.

    http://www.tohatsu.com/accessories/prop.asp

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