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Thread: Outboard size for 15.5 ft inflatable

  1. #1

    Question Outboard size for 15.5 ft inflatable

    Hi folks,
    I'm looking to buy a 15.5 ft inflatable boat and need suggestions on the size of the outboard to put on it.
    The boat is rated for up to 50 hp motor with 235 lb as a transom limit. I plan on boating on lakes and
    saltwater out of Seward, Homer, and Wittier. 3-4 people, plus some camping/fishing gear.
    The boat will be stored on the trailer most of the time.
    I looked at Yamaha, Honda, and Suzuki 4 stroke outboards (want to keep it Kenai legal) and found that
    40-50 hp range puts me right against the transom weight limit - I think 40 hp Yamaha is 224# with the
    tiller. So is 50 hp Honda.
    Going down in hp lowers the weight some - e.g. 30 hp Suzuki or Honda weighs in at 160 lb.
    Would 30 hp do the job well enough or should I go with the higher hp?
    Anyone has/had similar set up - how did that work out for you?

  2. #2
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    I'd go with the 50, especially if you're looking to haul 3-4 people and camping gear.
    "When everything seems to be going against you, remember that the airplane takes off against the wind, not with it."
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    Member ChugiakTinkerer's Avatar
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    I have a 13' inflatable with a 30 hp Tohatsu two stroke. It has no problem getting on step with three people in it, but adding a fourth and gear adds a lot more time to getting on step.

    I imagine you're planning on spending a fairly significant amount of money on this purchase. I would try find a way to test drive comparable boats in the motor sizes you're considering.

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    Member cod's Avatar
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    I have Tahatsu 40 two stroke (detuned to 35) on my 15.5 Achilles and get 23-24 mph out of it with two people. (Mine has small steering console and big cooler w seats mounted on it).
    I would think u would want to go bigger rather than smaller on the motor. Then the next thing will be playing around with props of various pitches to get the best performance out of your boat and motor.
    Your sarcasm is way, waaaayyyyyyyy more sarcastic than mine!

  5. #5

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    Well, two out of four are kids, though they grow fast.
    I never owned a boat before. Any concern about putting the max weight on the transom of an inflatable?
    Like trailering or handling with lighter loads.
    Can two adults mount a 224 lb outboard on/off without getting a hernia?
    Thanks to all who replied!

  6. #6
    Member cod's Avatar
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    I doubt you're gonna want to put a big motor on/off your boat every use. That means in/out of the truck, garage, shed, etc. Major pain in the back. Can it be done? Sure. But major pain.Remember how wet, slippery launch areas will be. Not conducive to awkward mounting of motors.
    I'ld think you want a trailer (mine's all aluminum and ultralite) and always have the motor on the boat.
    Your sarcasm is way, waaaayyyyyyyy more sarcastic than mine!

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    I ran a Yam 25 2-stroke on a 16' Zod. That was about all the power I wanted; about 20 mph. Even those can flip if you get nutso. A friend ran a 35 on one and it was apparently quite fast. Good luck.

  8. #8

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    How heavy load did you have to get 20 mph?
    Quote Originally Posted by jklingel View Post
    I ran a Yam 25 2-stroke on a 16' Zod. That was about all the power I wanted; about 20 mph. Even those can flip if you get nutso. A friend ran a 35 on one and it was apparently quite fast. Good luck.

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    light. guessed at speed.

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    I have a JP Marine 15.5 and I run a 20 HP Yamaha four stroke. With two big guys and gear I can cruise at 16-18mph. It's light enough that I can take it off or put in on myself and it really sips the fuel. I mainly go out of Homer or Seward.

  11. #11

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    For many years I ran a 25HP Yami 2-stroke on a 13.5' Achillies. Solo and flat out that thing would flap your ears and cheeks, skipping across the water like a stone. No telling how fast I was going, but you wanted all the weight you could find up in the bow. With three big guys in it and an array of gear, it would get on step almost instantly, but again no idea of speed. Seemed like plenty for going upstream on a river, but that's a guess because it was ocean only.

    Guesses are free and come on rolls of toilet paper, but I'd be comfortable with a 15.5 wearing something in the 30-40HP range, on the lower end on the ocean and perhaps higher end for running up rivers. For my geezerly sensibilities a 50 seems like overkill, especially for solo use on the ocean. A bud has a 50 on a 15' (?) rigid hull. Might be a 16' but memory fails. I startled him badly one day when I outran him with my little 13.5 floorboard model with that 25, but I just barely did it. Of course, I was only hitting the water every now and then while he was cutting the waves in much greater safety and comfort on top of that rigid hull.

  12. #12

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    BrownBear, thanks for the informative reply!
    50 hp seems like an overkill to me as well, even though I don't know much about inflatables. Heavy to boot.
    So far, I'm leaning towards the 30hp Suzuki 4-stroke which weighs about 160 lb. It is the lightest in its class, fuel injected, and
    has a pull start - i.e. no need for the battery. Still heavy, but more manageable than a 230 lb-er.

    Quote Originally Posted by BrownBear View Post
    Guesses are free and come on rolls of toilet paper, but I'd be comfortable with a 15.5 wearing something in the 30-40HP range, on the lower end on the ocean and perhaps higher end for running up rivers. For my geezerly sensibilities a 50 seems like overkill, especially for solo use on the ocean. A bud has a 50 on a 15' (?) rigid hull. Might be a 16' but memory fails. I startled him badly one day when I outran him with my little 13.5 floorboard model with that 25, but I just barely did it. Of course, I was only hitting the water every now and then while he was cutting the waves in much greater safety and comfort on top of that rigid hull.

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    Member Alangaq's Avatar
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    I had a 15 ft Zodiac with a 25 hp 2 stroke Johnson. motor was 115 lbs, and about all I could handle when I pulled on and off for winter. Not so much the weight, but no real easy way to lift and carry it. With wife and three kids under 10, it would top out at 22 mph according to gps. Up on step easy and fast. But I got to tell you, 4 or 5 folks in that sized inflatable is really tight! Add fishing and camping gear and.. well, you get it.


    Also, a trailer is a must. Breaking down and reassemby is a real pain.
    “You’ve gotten soft. You’re like one of those police dogs who’s released in to the wild and gets eaten by a deer or something.” Bill McNeal of News Radio

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    Member Bullelkklr's Avatar
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    We ran a 15.5 zodiac for 3 years - mostly on the salt. Owned her for 6. It had a 40hp zuki with 35hp labels on the cowling. It was sufficient with most loads and overkill solo (if there is such a thing). We would load her up heavy heavy for weekend camping in PWS and most of the time could get on step when conditions allowed.

    I took her across the inlet over to the Su one time with my uncle, on a week long moose hunt. She was loaded for bear. We did not get on step going over, but coming back with the same load (added a bear) we got on step with the tide and came into port at 29mph on the GPS.

    Most days it would go 24-26mph. The 40hp was perfect, but there were times I wished for a 50hp 4 stroke.

    I sold that little boat a few weeks ago. Bittersweet.

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    Sounds like you've had lots of fun with that boat! How heavy was that 40 hp Suzuki? Was it a two stroke? Did you have to put a hydrofoil on it?

    Any suggestions on the brand for an inflatable? Are zodiacs better than say Achilles or JP Marine?
    Thanks a lot guys! Unfortunately I don't have an opportunity to test any of the boats being here in Anchorage.
    However, I'm learning a lot from your replies.

    Quote Originally Posted by Bullelkklr View Post
    We ran a 15.5 zodiac for 3 years - mostly on the salt. Owned her for 6. It had a 40hp zuki with 35hp labels on the cowling. It was sufficient with most loads and overkill solo (if there is such a thing). We would load her up heavy heavy for weekend camping in PWS and most of the time could get on step when conditions allowed.

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    Member Bullelkklr's Avatar
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    It was an injected 2 stroke (no gas mixing). Circa early 1980's. No hydrofoil. I don't know much about the new inflatables.

    I do know one thing though - they lack in comfort but are good on versatility. I sold the setup cheap...2600.00 to a couple here in town. Hopefully they are getting some use out of her.

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    Wow, that's a lot of stuff! Looks like it would be hard to see in front of it with all the gear piled up.
    Thanks for sharing!

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