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Thread: Will a 9.8 hp Tohatsu get me on step?

  1. #1

    Default Will a 9.8 hp Tohatsu get me on step?

    I have been a fan of this forum, always a reader, never a writer. But, this time I need help on a decision from someone with personal experience - I know you are out there - so get on the keyboard and lend me a hand.
    Here Goes.....
    I have an 11' 9" Titan inflatable sport boat with aluminum floorboards. For the past couple of seasons I've flown it and a 6 hp Tohatsu 4 stroke outboard out to camp on fishing and hunting trips. With 2 fairly small men and light gear the boat will get up on step. 3 men and a days worth of gear and we plow along at 5 knots and chat for hours watching the scenery go scrolling past. Very economical, and easy to pack that little outboard - but I want to upgrade and get a larger outboard capable of planing the boat with 3 men and a days worth of gear aboard. Portability is a big factor. We need to be able to carry the boat and motor above the high tide line at night and such - plus be able to load the outboard on and off the plane, charter boat, whatever. I much prefer 4 strokes but they do get heavy for packing around.
    Tohatsu/Nissan makes a 9.8 hp 4 stroke that weighs about 81 lbs - fairly light weight but nearing the 100+ pound mark where all kinds of 15 hp outboards come into play. Will the 9.8 hp Tohatsu get 3 men on step in my boat? (very similar hull to a 380 zoom, or classic 12'5")
    And....
    Is there any practical power difference between the 9.8 Tohatsu and the Honda 9.9 hp power thrust? (The Honda weighs 92 lbs).
    Anybody out there own a Tohatsu 9.8, or Honda 9.9, and get an 11' 9" inflatable on step with 3 men and fishing gear?
    Thank you in advance for your time and effort.

  2. #2
    Member AKBighorn's Avatar
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    I used to have a 10'6" zodiac with an inflatable keel and composite floorboards. I used a 9.9hp yamaha 2 stroke. It pushed 3 guys and fishing gear up the big sue but after catching 2-25+ kings we floated down underpower. The zodiac and the motor were both right at 100lbs each if I remember correctly. I don't know for sure but it seems like a 9.9hp motor is a 9.9hp motor. Hope that helps.

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    I'm not familiar with Tohatsu motors, but here's the rub with the other brands. Typically a 9.9 is a derated 15. Same powerhead, same weight, less power. It's been that way for as long as I can remember. I never could figure out why people bought 9.9's. I jumped to the 15 to get maximum output per pound. My 15 Yamaha 2-stroke weighs 80#. It goes with my little Quicksilver blow-up boat that weighs 64#. An old Yamaha 4-stroke is at least 25 pounds heavier. That doesn't seem like a good thing to me. The new Yamaha 15 shares the same powerhead as the 20 and gains 20-some pounds over the old 4-stroke. Better than 50% heavier than my 2-stroke. That would make the motor twice as heavy as my boat. No thanks.

    I still have my first Yamaha 15 2-stroke. It's over 20 years old. I'd bet that the first time I pull it this season it'll start. I say that because it's done so for 20 seasons. 1st pull. Every time. No maintenance. That motor is incredible.

    I looked it up. Tohatsu 9.8 is 81# while their 15 is 115#. How much do you prefer 4-strokes?
    Last edited by Mr. Pid; 04-03-2007 at 07:47.

  4. #4
    Moderator Paul H's Avatar
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    I'd also vote for finding a 15 horse two stroke. Light weight, decent power. You'll give up some fuel economy, but trying to push 3 people and gear needs power and the 9.9 is still going to be on the marginal size. The rule of thumb is your gross weight, ie hull, engine, crew, gear should be at most 40#/hp, which puts a 9.9 @ 400 lbs, and a 15 @ 600 pounds.

  5. #5

    Default I doubt it will get 3 guys/gear on step

    We used to have a 10'6" Zodiac as a dinghy with an 8 horse and two guys could get on step but three guys wouldn't even come close. I doubt the 9.8 will will be enough. I would go with the 15 2-stroke as well. The high thrust Honda and other similar are designed more for kicker duty as they have lower gear ratios and swing larger props.

  6. #6
    Member breausaw's Avatar
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    Run a 2004 two cylinder 9.8 Tohatsu 2 stroke pushing a 14ft Portabote. The boat will plane along nicely with 3 or 4 adults; boat at 90 lbs and motor is 60lbs wet. I bought the 2 stoke for its weight and portability; itís not a d-tuned 15. Some EPA regulation kicked in and Tohatsu had to quit selling these motors in the US.
    Marita Sea & Ski bought up a ton of these motors before Tohatsu quit selling them and may have some left.
    This motor burns clean for a 2 stroke and wonít leave you smelling or oil at days end. For the money this motor gives a lot of bang for the buck. Not sure if it will push an inflatable the size you have as well as my Portabote.

    FYI, Tohatsu, Mercury, and Nissan come out of the same factory.

    Hope this helps,
    Jay

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    The quick answer is no. Up to 900 lbs of gross weight, including boat,engine, fuel, gear and people, it will plane. Anything over that and it will be luck. The 9.8 Tohatsu 4-stroke is a great little engine, but it suffers the same drawback that all 4-stroke engines suffer....No hole shot. Since there aren't any 2-strokes left anymore(except DFI's) due to the EPA, you really need to go to a 15, 18 or 20. Or buy used.

    High thrust model engines, regardless, of brand sacrifice all speed potential for low end thrust. You would be in worse shape with one of those.

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