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Thread: need advice on what motor

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    Default need advice on what motor

    i am looking at buying a 18ft alumacraft 08 and was triing to decide between a Merc 90hp or the 115hp jet. if anyone has any adivce that would help me with my choice it would be appreciaied. thanks p.s. not the four strokes

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    Member AKRoadkill's Avatar
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    Not too many folks complain about being overpowered. All else being the same, I'd opt for the 115 over the 90.

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    Member Akgramps's Avatar
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    The boat is never too big unless your stuck on a sand bar........
    You never have too much gas unless your on fire!!!!!!!!!!!!!
    And you never have too much power..............

    Seirously it depends on how much you want to haul, bigger motor will haul more weight. It seems with todays efficent motors a bigger motor will allow you to back off on the throttle and you may actually burn less fuel, I think often times boats are set up underpowered, ok if you are mostly fishing and not planning on trying to put large dead animals in the boat.

    Be wary of buying a jet motor set up on a prop tunnel.


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    Why be wary of setting up a jet on a tunnel boat?

    Wooldridge sells many tunnel boats a year that are equipped with jet motors and I never heard anyone complain or am I missing something? Isnt this why the tunnel hull was devised in the first place? For jets?

    As far as motors go I would absolutely stay with a 2 stroke for jet useage and would recommend you look at the Mercury Optimax. My research tells me they are most likely the most fuel efficient outboard at cruising speeds on the market today.
    Tennessee

  5. #5

    Default Fuel economy

    Quote Originally Posted by Snowwolfe View Post
    As far as motors go I would absolutely stay with a 2 stroke for jet useage and would recommend you look at the Mercury Optimax. My research tells me they are most likely the most fuel efficient outboard at cruising speeds on the market today.
    Did your research include the GoDevil Surface Drive?

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    Yes it did and what you are promoting will not move my boat as fast as I want to go when it is fully loaded. Plus I do not like hanging on a tiller all day long as I steer the boat.
    Now if godevil is making a 200 hp motor that weighs the same or less than my Optimax and has remote steering then I am all ears to listening to you for the next time I purchase a outboard motor.
    Tennessee

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    Default Differant brand

    Mercs are OK, but they tend to blow reed valves when they catch air.

    I would go with the 115. You loose 30-40% hp by going to a jet.

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    Quote Originally Posted by Snowwolfe View Post
    Why be wary of setting up a jet on a tunnel boat?

    Wooldridge sells many tunnel boats a year that are equipped with jet motors and I never heard anyone complain or am I missing something? Isnt this why the tunnel hull was devised in the first place? For jets?
    There is a difference between prop and jet tunnels. And you lose even more power if you set up a jet on a prop tunnel because the prop tunnel is deeper. Wooldridge puts jet tunnels on their boats. All the alumacrafts I have ever seen have had prop tunnels.
    "When everything seems to be going against you, remember that the airplane takes off against the wind, not with it."
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  9. #9

    Default River

    Rivers vary a lot in AK. some allow the use of propeller operation, and some require a shallower draft i.e.jet. HP for HP a propeller driven motor is 25-30% more fuel effecient than a jet. In this day and age of rising fuel cost, will that be a factor? You can always factor in the power lost by adding a jet and increase motor size, there again yo will use more fuel. The larger 115hp jet still won't be as fast as the 90 hp propeller drive.Catch 22. Speed costs money, HOW FAST YOU WANNA' GO?
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    Member Akgramps's Avatar
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    What I said was " Be wary of buying a jet motor set up on a prop tunnel"
    I know, sometimes I read things fast and miss the whole point, i should have been more specific.
    As riverboater pointed out there is ahuge diffrence betwwen jet and prop tunnels, a prop tuneel looks (and I have never measured one) like it is 6-8" tall whick would place the jet way too high.
    Alumicraft does offer a jet tunnel in their 17 footer, why the local dealer is using prop tunnels is beyond me????
    I will try to attach a photo so it can be seen.
    Maybe some one knows how well this is working?
    Last edited by Akgramps; 03-21-2010 at 22:56.

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    Thanks for the education. I never knew there were specific tunnels for props vs jets. I thought a tunnel was a tunnel.
    I apolgize for getting off track of the original question.
    Tennessee

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    Quote Originally Posted by brav01 View Post
    Rivers vary a lot in AK. some allow the use of propeller operation, and some require a shallower draft i.e.jet. HP for HP a propeller driven motor is 25-30% more fuel effecient than a jet. In this day and age of rising fuel cost, will that be a factor? You can always factor in the power lost by adding a jet and increase motor size, there again yo will use more fuel. The larger 115hp jet still won't be as fast as the 90 hp propeller drive.Catch 22. Speed costs money, HOW FAST YOU WANNA' GO?
    True. I thought he was asking about a 90 hp jet vs. a 115 hp jet. a 90 prop vs a 115 hp head with a jet unit is a different story. In this case the prop would be more efficient and have more "power", as a 115 head with a jet unit will be about 80 hp at the jet.

  13. #13

    Default fuel economy

    Quote Originally Posted by Snowwolfe View Post
    Yes it did and what you are promoting will not move my boat as fast as I want to go when it is fully loaded. Plus I do not like hanging on a tiller all day long as I steer the boat.
    Now if godevil is making a 200 hp motor that weighs the same or less than my Optimax and has remote steering then I am all ears to listening to you for the next time I purchase a outboard motor.
    Fair enough. 20 mph upstream and 28 downstream in a 24' jon is fast enough for this old retired guy. On my income, I like 7 to 10 mpg because I can still cruise the Yukon for Pike holes. I couldn't afford the Optimax or the fuel to run it. I'm happy for you that you can.

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    thanks for the info guys. the boat has a deep tunnel and both motors i was asking about where jets.

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    so what is the differece between a prop tunnel and a jet tunnel? i have seen props with shallow tunnels and most jets with deep tunnels. I did not know that there was a differece.

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    The diffrence is, a jet tunnel is usally 2 -1/2 to 3" tall and it is usally wider than a prop tunnel. the reason I suspect is because on a jet, the intake is in front of the prop shaft (long vertical shaft that drives the prop or jet) so as the intake foot pivots when you steer the boat, the intake is continously recieving a clean flow of water.
    On a prop unit the prop is behind the prop shaft and so it is farther away from the transom and therfore the boat will work with a narrow tunnel.
    Any tunnel will affect displacement, (the natural bouyancy of a particular boat and how it floats in the water) That is why tunnels should be no bigger than necesary to do the job.
    If you look at the exit end of a jet you will see the outlet, and notice it is up some distance from the bottom of the jet (intake side). If the jet outlet (propulsion) is to high out of the water it will not be efficent. The water coming out has to have something to push against.
    Wooldridge and speciality developed the jet tunnel design years ago and if you do some looking on the internet you can find some specific information about the most optimum shape of a jet tunnel. If in doubt call speialty jet in San bernadino ca. They are good people. Speciality is the sole manufacturer (to my knowledge) of out board jets.
    I have no personal experience with aprop tunnel and dont know why someone would buy one except it would raise the prop w/o the normal 30% reduction in horsepower when you go to a jet.
    Alumacraft makes a 17 foot boat with a jet tunnel, or at least they show one in their catalog.
    I asked this question several weeks ago after seeing these boats at the Carlson center and this is the response i got. http://forums.outdoorsdirectory.com/...ad.php?t=29595
    If still in doubt call alumacraft and ask them.
    As fas as 90 or 115, in my opion bigger is always better when it comes to outboards. If you only plan on using it for fishing, the 90 will be fine. if you want hunt and put a moose in the boat, buy the 115.
    Let us know what happens and what you buy....................Good luck

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    Member Akgramps's Avatar
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    http://forums.outdoorsdirectory.com/...54852#poststop

    I am trying to post a link to a question i asked 2 weeks ago "jet on aprop tunnel"

    If the link doesnt work you can got my personal page and acess it from there.


    ##@@&&** blasted computers@@#&***

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    thanks gramps. i looked at your post and i am going to to do some more research on those deep tunnel alumacrafts. my friend has one and seems to love it but it is nice to have a differfent opion. thanks alot for the great info. going to do some more looking now. I will let you know what i decide.

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    Bigger is better, go with the 115Hp.All the reason,s stated above, Back off the gas stay on step less fuel. And when you load it down you going to wish you had that little extra..

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    I couldnt take it, so I e-mailed Alumacraft, and this is the response.
    Hopefully it will paste OK.
    Of course it reads in reverse order!!!



    Truthfully we have tested the boats here like he has them setup and they want to cavitate really bad. I do know that the difference in altitude helps that situation though. We do not recommend it in the lower states because of this but I do have dealers in Utah & Idaho that use the same setup and it appears to be working for them. The trouble we experience is the water flowing through that deep tunnel mixed with the air and then pulling through the bottom of that pump. If a dealer purchases a setup like this down here they will weld a plate and close off the entire tunnel except 2” so the pump can pull the water correctly.
    Thanks!
    Peewee Strother
    Sent: Friday, May 16, 2008 11:35 AM
    To: peewee@alumacraft.com
    Subject: RE: ALUMACRAFT JET TUNNELS
    Peewee,
    Thank you for the reply, I am disappointed to hear the Jet tunnel has been dropped. I am curious as to how a jet drive on your prop tunnel would work?
    A dealer in my area is setting up boats in this fashion, It doesn't look right?
    And I am wondering if this an acceptable method.
    Looking forward to hearing from you,

    -----Original Message-----
    From: Peewee Stother [mailtoeewee@alumacraft.com]
    Sent: Friday, May 16, 2008 4:40 AM
    Subject: ALUMACRAFT JET TUNNELS
    Sir,
    I do appreciate the interest. We have deleted the only model we ever built with the Jet tunnel for 08 model year due to slow sales of the boat. It was the model 1756 RiverRunner. The boat had a 2” jet tunnel with a 27” transom. We have some dealers that still have the models in stock. One dealer is LaCanne Marine in Faribault MN 507-334-6415. The boat ran really shallow and actually ran better with the 90 /65 jet than the 115/80 jet. Anyway this is the only model we built and at this time do not have any plans to bring back a jet tunnel.
    Thanks and have a nice day!
    Peewee Strother
    Sales Coordinator
    (870) 246-5555 Ph
    (870) 246-4507 Fax

    Does Alumacraft still offer a jet tunnel hull option?
    I have seen it listed as available on a 17 footer in past catalogs, however I could not find it in the online catalog.
    If not available can a jet drive outboard be installed on a boat with a prop tunnel with satisfactory results?
    If so are there any drawbacks?
    Thank You,
    Last edited by Akgramps; 05-19-2008 at 09:18. Reason: e-mail

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