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Thread: Power to Weight Ratio

  1. #1
    Member Kmagers's Avatar
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    Default Power to Weight Ratio

    Ok guys, im looking into buying a 20' thunderjet. It has a 115 prop on it when i jet it it will be 81ish. I plan on running some interior rivers such as chena, tanana, chitina also. When i take it to the salt ill put the prop back on. Im worried this might be a little under powered for moose camp with the jet on. Anyone got some literature for me or insight, first hand knowledge...... Its a 20' luxor thunderjet.
    Trying to play enough to make working for the money all worth it.

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    Member oakman's Avatar
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    That's what I would kinda guess. I used to own a 20' seaark with a 115hp on it. With the prop, it was a beast. It would jump up on step with a huge load without a problem. But with the jet on, totally different story. From my experience, the jet was great with lighter loads, not much use for heavier loads.

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    Member KantishnaCabin's Avatar
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    If your goal is to do some moose hunting with the boat then I would advise you to just leave the prop on. The Tanana and Yukon have hundreds of river miles you can access with that boat using a prop. If you jet that 115 you will be very limited in load carrying ability. You would probably be ok for 2 guys and a lunch sack, but forget hauling out a whole moose and gear.

    Forget the jet and use a prop for a few years. If you find that you want to go a little further than your boat can take you then you would be best to repower the boat or get a different boat. But you will be hard pressed to hunt all the areas you CAN access with that boat on the Tanana. Lots of moosey places you can get to with a prop.

  4. #4

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    I'm curious if a jet would even work very well on the hull of the boat you are looking at. I think the luxor has a 16 deg V hull which may not work very well with the jet. If this is the boat on craigslist right now you will also need to consider the extra weight of the hard top.

  5. #5
    Member Kmagers's Avatar
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    the dry weight with top is 2625. already looked at the weight to power ratio. 40 lbs per horsepower is what she comes to with the jet. that is including the hardtop.
    Trying to play enough to make working for the money all worth it.

  6. #6
    Member KantishnaCabin's Avatar
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    If you are going to be running mostly interior rivers and the occasional trip to Valdez then you should probably be looking at and inboard jet.

  7. #7

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    Found an article about selecting jet HP for boats. They recommend the following.

    A safe guideline for selecting the right size engine: You need a ratio of 1hp for every 25 pounds your craft will be pushing. Use the engine powerhead rating, not the jet rating.

    You would be about right at the limit with the 115 and the dry weight. Adding fuel, people and gear would probably put you under powered.

    Here is a link to the article with a graph that can be used as a reference.

    https://www.fishandboat.com/Transact...ts/jetboat.pdf

  8. #8
    Member Jimw's Avatar
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    Quote Originally Posted by KantishnaCabin View Post
    If you are going to be running mostly interior rivers and the occasional trip to Valdez then you should probably be looking at and inboard jet.
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^
    100% agree
    2005 20' Weldcraft Sabre XL 350 MP
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  9. #9

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    Ran an 18' Jetcraft with a 90/65 for 15 years doing exactly what you are describing. It was great for fishing with 3 people and if you watched the hole shot 4 people. Loaded with gear and weight was a different story. Took it hunting a few times. Once I hauled out a small moose with 2 adults, three kids, and dog. Had to be wot the whole time to keep on step. Long story short for what you are wanting to do, especially with a TJ Luxor, I'd think you'd want at least a 150/105. As has been recommended already what about an inboard? I went up to a 20' NW jet this last year with a 351. I run lakes and rivers and took it out of Valdez 4 times. No problems hauling weight and getting somewhere quick.

  10. #10
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    For me it would be underpowered with the PROP on! I'd want a minimum of 150/105--and I recommend staying away from Chitna with that 115/80 setup unless your life insurance policy is current.
    What are you planning for height adjustment for the prop/jet switch? Lift, or plates? If you're using a lift, you're losing even more power due to the setback.

  11. #11
    Member HCL's Avatar
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    Agee with the others, would look for inboard jet for what you are looking at doing.
    Also, i have never heard anyone complain about "too much power" but you hear more often than not, "wish i had more power"
    Just my 2 cents
    Mike

  12. #12
    Member akaviator's Avatar
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    My 6.2L L86 powered Wooldridge Sportstour with full fuel and 1000 lbs. of payload is at or under 12:1.

  13. #13

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    Quote Originally Posted by KantishnaCabin View Post
    If your goal is to do some moose hunting with the boat then I would advise you to just leave the prop on. The Tanana and Yukon have hundreds of river miles you can access with that boat using a prop. If you jet that 115 you will be very limited in load carrying ability. You would probably be ok for 2 guys and a lunch sack, but forget hauling out a whole moose and gear.

    Forget the jet and use a prop for a few years. If you find that you want to go a little further than your boat can take you then you would be best to repower the boat or get a different boat. But you will be hard pressed to hunt all the areas you CAN access with that boat on the Tanana. Lots of moosey places you can get to with a prop.
    This is about the best advice you can get having done it both ways. The biggest problem with a jet, as I see it, is without knowledge of the water one can get rather badly stuck whereas a prop telegraphs the bottom. Not to say that I haven't planted myself with a prop...

  14. #14
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    Quote Originally Posted by akgriz View Post
    I'd want a minimum of 150/105
    If you are hellbent on staying with an outboard, this is very accurate...

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