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Thread: What is the biggest jet unit an Alweld 18X4 ft will run?

  1. #1

    Default What is the biggest jet unit an Alweld 18X4 ft will run?

    Ok, I have an alweld 18x4 ft flat bottom does not have a tunnel on it..and i think that it is a 22 inch transom?....

    what is the biggest jet unit i can put on it?....I've been told by a guy at the boat shop that there is a light weight 90 hp 2 stroke that can handle it if i do the remote steering ....

    don't care about gas mileage, got the money...but, recommendations are appreciated for models, hp, etc....the guy also said that a 70 hp jet yamaha 2 stroke would do good, but that the 90 weighs the same....dang, i dont' ahve my notes with me...i would like one that is convertible between prop and jet..

    my boat says 50 hp max with remote steering...but the motor i have on there now is a 35 hp and weighs at least 300lbs.....with me in the back running it.....

    Scotty in the AK bush

  2. #2
    Join Date
    Apr 2006
    All-I-SAW, AK.

    Thumbs up

    My cousin down in Washington runs a Smokercraft (newer welded model) with the same dimentions as your Alweld, and he has a 4 stroke Yamaha 90/65 jet. He had the tiller set up and converted to the center console after the first year, mainly to get some weight forward. 4' isn't very wide and it sits a little deeper in the water then a 5 or 6 foot wide boat. It was taking a bit longer to get on step too. It goes just fine with 3 guys and a days worth of fishing gear once on step. He put a 185 Honda 3 wheeler, his camp and a 5 point bull elk in it and it did great. He also does surprisingly well in the mileage department.
    I don't know about how beefed up your transom is to hold any extra weight if you upsize, but his transom on that Smokercraft was pretty stout from the factory. I'd weld a gussett or a stiffener in it somewhere anyways mainly because the roads are bad up here and they get bounced around sometimes creating uneccessary cracks from flexing/vibration. I swear that you'll get more damage on a boat from trailering it up and down the highways up here then you will running it. IMO...
    I'm pretty sure that almost all of the motors that have jets can be converted to a prop-job. I've heard that "some" motors are built specifically just for jets and shouldn't be converted. I can't confirm that theory, it's just things you hear now and again. Play it safe and ask the manufacturer and/or the saleman to be sure.
    The placard indicating 50hp max on the hull is for manufacturer liability reasons. They don't want guys taking a 16' boat, beef up the back, slap a 150hp VMax on there and then go out killing themselves. You can "usually" go a little bit above that placard recommendation, just don't over do it. I've done it myself to one of my earlier river boats a few years ago and was very glad that I did. I went from a 115/80 jet (factory recommendation) to a 150/105 jet. It was nice having that extra power when I needed it, especially with a load. It made a night and day difference a few times. The mileage was similar when cruising, but I also wasn't working it as hard as I was with the 115. When I stepped on it, economy went down the toilet, fast!!!
    I've also heard hear and there that the newer Suzuki 4 strokes are some of the better running engines these days and are some of the lightest weight-wise in the industry. Something to consider for ya. But, since there are more Yamaha mechanics and motors here in Alaska then Suzuki, if there's a problem, then maybe Yamaha is the way to go. Who knows, shop around.

    Anyways, my .02.. Good luck to ya...

  3. #3
    Join Date
    Jun 2007

    Default 75hp good to go

    I have 20' X 52" flat bottom with an OMC 88hp that weighs in at close to 360lbs. I have used it for years, and even though I have 2 other boats refuse to get rid of it.
    The torque and power are very good. But in reality, the 3 cylinder 70, 75, or 90 would be lighter and offer comparable power, but maybe a bit less torque out of the hole. I think the Yammy's are coming in around 270lbs or so which is considerable for that size boat. The 70's would generally use less gas.
    If you want a big motor, I agree with Swampdonkey, and really beef up that back end.
    Riverboater just bought the 90 Yam and seems to like her pretty well. He is running that on a Marion 18' I believe, but with a prop, not a jet.
    When I was shopping motors, I looked pretty hard at the Johnson 4-stroke that was built by Suzuki. The 140hp was using the big Super Pump on the jet, the same as the 200hp and up. Maintenance around here was a bit of a concern though, so went with the Yam myself.


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