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Thread: Outboard upgrade?

  1. #1
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    Default Outboard upgrade?

    I currently have a 85hp yamaha jet 2 stroke on my 18ft jon boat. I can get a smoking deal on a new mercury 50hp prop motor. The yamaha is a 1989 and the mercury is a 2009. I can't use my boat to dipnet on the Kenai, so I end up renting boats every year.
    Do you think I should go for it, or will the loss of hp make me regret it?
    Just looking for opinions.
    Thanks,
    Matt

  2. #2

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    Quote Originally Posted by Coopspa View Post
    I currently have a 85hp yamaha jet 2 stroke on my 18ft jon boat. I can get a smoking deal on a new mercury 50hp prop motor. The yamaha is a 1989 and the mercury is a 2009. I can't use my boat to dipnet on the Kenai, so I end up renting boats every year.
    Do you think I should go for it, or will the loss of hp make me regret it?
    Just looking for opinions.
    Thanks,
    Matt
    There are a few things to consider that jump out at me.

    1.) If the 85hp rating is at the head versus at the "prop", then running it with a jet means that your effective horsepower is somewhat less, just guessing in the range of a 70hp at the jet unit. I am not an expert by any means on this, but know that some motors lose efficiency when using a jet versus a prop. You may be only looking at a difference in available horsepower of 15-20 rather than 35 (85 now to 50 with the newer one).

    2.) What are your other uses for the boat? Do you need a jet for where you go or are you just fine with a prop? If you need a jet and will need to convert that newer 50hp (at the prop) to a jet, then you will have less than that effective when all is said and done.

    3.) What you have in the boat and the physical characteristics of the boat are probably the biggest factor. If it is almost always just you and a buddy and a few bags of gear, you are probably fine with a 50hp. On the other hand, if you are normally hauling a group of people for longer trips with more weight, you may have a hard time getting a 50hp setup on step. Its hard to tell which side of the line you are on until you cross it and find out the hard way though...

    Sorry I couldn't provide any solid opinions, but maybe help to ask the questions....

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    Thanks. That is the problem though. I don't want to spend the money and find out it isn't enough. I don't hunt out of the boat now, and I only run to the Deshka and the on the little su. I think I am just going to do it, and keep the 85 until the 50 proves itself.
    Thanks again.

  4. #4

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    Dunno about the jet/prop comparison, but I can tell you this about a 50. I'm running a 50hp Yamaha 4-stroke with a standard prop on a 20' Hewescraft Open Fisherman, hull weight around 1k. Sounds under powered, doesn't it? You judge: With 4 people in it, it will do 24.5 mph (a la GPS) at 5,000 RPM and top out at about 26.5 at 5400 RPM. Best of all, it is really stingy on gas. I just came in from 4 hours of trolling and about 15 miles running altogether. Total fuel consumption was somewhere on the shy side of 3 gallons. I had a kicker can with 5 gallons in it rather than 6, and it's half full now if you want to check my math.

    How heavy your boat is and the load will determine a lot, but my instinct is you just might be pleasantly surprised if you don't need the jet and don't need to top 30 mph.

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    Thanks BB. I would get a jet to run to Deska and the little su, but would use the prop for the Kenai. I guess my real concern would be with using the jet unit.
    Thanks again.

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    Get an engine hoist and swap the 50 in for dip netting then the 85hp jet for the rest, that's what I do for my heavy 20' Koffler sled boat with a 140jet and 50 prop. It's a bit of work but worth it. The 50 should do fine on an 18' jon boat for netting but you'll need the jet if you're planning on running the Little Sue and Deshka. A 50 prop will push it fine, but if you put a jet lower on it you'll be running 35hp at the pump vs the 60hp at the pump you are running now. I ran a 55 hp Johnson with a jet on a riveted 16' john boat (light) with a couple guys and fishing gear it was ok but underpowered if I wanted to hunt out of it or haul any load. I highly doubt you'll be happy with a 35hp jet (50hp power head) on your 18' jon boat once you put any load in it.

  7. #7
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    You lose 30% of rated HP with jet. Yes you'll regret going to a smaller motor. Use the jet when you need to and switch back to prop for good water.
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  8. #8
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    My uncle has a 18 foot smoker craft kodiak with a 50hp effinrude etec on the back. He has an electric/hydraulic lift and both prop and jet.

    We put the prop on it last year and went to Deshka. 3 people, 1 dog, light camp gear. Replaced the health drinks (barley pop) with King fillets and although it would go back up the Su, we weren't breaking any record speeds......barely above hull speed.

    Going u the deshka with 3 people, dog, and fishing poles it went okay. Poor holeshot. No real speed - 18mph.

    With the prop out in PWS it does fine. 27-28mph with 4 big guys, a dog, rifles, fishin gear.

  9. #9
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    Quote Originally Posted by Coopspa View Post
    I can't use my boat to dipnet on the Kenai, so I end up renting boats every year.
    Why? I'm pretty certain you can unless the rules for dipnetting below the bridge on the Kenai changed in the last week!!!! If they did, there were over a 400 illegal boats out there dipping, me included....

  10. #10
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    Quote Originally Posted by swampdonkey View Post
    Why? I'm pretty certain you can unless the rules for dipnetting below the bridge on the Kenai changed in the last week!!!! If they did, there were over a 400 illegal boats out there dipping, me included....
    If you were running a 2 stroke motor as he states in his first post his old 85 HP is then yes you were illegal.
    Not by HP but by being a 2 stroke.
    That rule is not new either.
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