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Thread: Need help with Yamaha jet unit.

  1. #1
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    Default Need help with Yamaha jet unit.

    I am hoping someone can steer me in the right direction, we have decided to go ahead and get a jet unit to bring with us up the Koyukuk this year. I have a 2000 F100 and am not sure what options I have, and cant seem to find the info. What lower units are interchangeable? I know I need a jack plate also, does anyone in AK have these in stock?

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    Converted my 2000 F100 to a jet 3 years ago. love it!

    Go here: http://www.outboardjets.com/index.php .... find info on jet units / dealers in town. Yes you will have to get a transom lift between 6-8 inches. AK Mining & Diving had some prefab'd and instock at the time (they looked a bit "under built") I had one made at one of the welding shops in Anchorage. I wanted one "over-built" (to handle 400 lbs of OB) they did a beutiful job and made it from 1/4 " Aluminum.

    Your question on interchangable lower units: If you mean jet to prop, then YES (as long as you have same drive shaft length) (say 25") Keep in mind you'll also have to change your engine height(transom lift) Deweys carries an adjustable jack plate, (More expensive then fixed plate)

    If you mean taking the jet from one engine and slapping it on your F100, your options get limited fast (see OB Jets website above)

    You'll save $ by doing as much of the conversion as is possible yourself... I remember the folks @ AK mining runing me a list that came to around 10K converting 50 Prop (tiller) to 100 jet (console steer). I did it myself for half that.

    It was an interesting project, I'm glad I did it, and happy w/ the results. If I were to do it again I might've opt'd for the adjustible jack plate giving me the lower unit change capability. Would've probly run me additional $1000-1500.

    feel free to shoot any questions my way. good luck

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    Dewey's for the jet. I would "strongly" recommend not going with a Jack plate option, rather give Ben a call at Silver Streak boat and he'll be able to set you up with a riser etc. But if you really want the jack plate, Dewey's as well. Expect to pay about $2200'ish for the jet and jack plate. Plus install if your not doing it.

    When you doing the Koyukuk? I am doing the second season... in all honesty though, if you have a prop, and your wanting this for the Koyukuk, keep your prop for the hunt, you'll be "much better off" with a prop. I am giving up a lot staying with the jet in regards to load and fuel.

    PM me with your contact info if you want to speak more about this.
    Tony

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    Power Tran for the power jack plate. http://www.powrtran.com/cgi-bin/cart...?parts_id=9662

    If you plan to switch back and forth between jet amd prop it makes life a lot easier, it has 7.5" of lift so allows some adjustment on either end for both lower units. The power tran is a jack screw, not hydraulic, so will not leak and lower. I am happy with mine, has worked flawlessly.

    Keep in mind it is a big lever on the back of the boat as it moves the motor some 5" back from the transom, and it will most likely have some effect on how fast your boat gets on step (will be most noticable with the jet) and how it sits in the water when drifting.

    If your boat has a tunnel, it will need to be extended some and some way to feed clean water to the jet.

    Other options are out there if you dont want a power lift.
    “Nothing worth doing is easy”
    TR

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    Thanks for the info. I have come across a jet unit from a 90 hp 2 stroke yamaha, that o.b. jets say will bolt up but the driveshaft is different, but they can get me the correct one. I am probably just going to go with a manual transom plate instead of electric or hydraulic,there are a few places I have found in state that have them in stock. As for why it is needed, I am just going too cary it with me for the run back up the Tanana to Nenana, last year by the end of season it was getting a little sketchy in places. Ref, do you know what impeller you are running?

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    I was running the three blade 7-3/8" ALum impeller that came w/ the unit (til I broke a blade 2 weeks ago) (too many gravel bar encounters) I ended up swapping out w/ a spare 4 blade SS that I found on CL couple yrs ago. Glad I had the foresite to buy and carry the spare... would've been a lond paddle home... I understand they have 3 & 4 blade in 7-3/8" AND there's a 7-3/8" "V6" variant (steeper pitch)

    I believe I've got the v6 variant because I'm not getting the full RPMs out of the motor w/ it.... (well the price was right, @ $100) I'm in the hunt now for a standard pitch 3 or 4 blade replacement.

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    Update, I have all the items together and will be going for a test run when I get off the slope, then go back to the prop and head for Nenana on the 10th. I have the manual jackscrew powerlift installed and seems to work fine with the dewalt. I have some concerns as to motor hieght, depending on trim position I may be a little low with the jet, but didnt have the shaft yet so we will see on the test run, I may have to drill some new holes. With the prop on it is a little higher, but I always felt it needed to be anyway. Think I might rig up a seperate cable for reverse so I dont have to mess with it on the river.

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    Update, I have all the items together and will be going for a test run when I get off the slope, then go back to the prop and head for Nenana on the 10th. I have the manual jackscrew powerlift installed and seems to work fine with the dewalt. I have some concerns as to motor hieght, depending on trim position I may be a little low with the jet, but didnt have the shaft yet so we will see on the test run, I may have to drill some new holes. With the prop on it is a little higher, but I always felt it needed to be anyway. Think I might rig up a seperate cable for reverse so I dont have to mess with it on the river.

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    Quote Originally Posted by kenaislider View Post
    Update, I have all the items together and will be going for a test run when I get off the slope, then go back to the prop and head for Nenana on the 10th. I have the manual jackscrew powerlift installed and seems to work fine with the dewalt. I have some concerns as to motor hieght, depending on trim position I may be a little low with the jet, but didnt have the shaft yet so we will see on the test run, I may have to drill some new holes. With the prop on it is a little higher, but I always felt it needed to be anyway. Think I might rig up a seperate cable for reverse so I dont have to mess with it on the river.
    Having done the jet to prop thing,, I can say that you will swear somebody stole half your engine when you run the jet. It has been my experience that the jet height is CRITICAL too low and it will drag and throw water everywhere.

    If you think you can swap from the prop to the jet and carry the same weight, you will be very disappointed.

    Another item to consider is that with the prop and the engine lowered, if you trim up the engine it can contact the transom. I had to have mine modified.

    I found that I could get by with 5 inches of lift travel, my sled has a tunnel and I can run the prop higher because of it and it gives me enough travel to get the jet in the sweet spot. Also notice the piece of plastic extending from the tunnel to the jet to keep clean water flow. I did for sure notice a performance loss, moving the jet back.

    Having done this hunt before, I would run the prop and carry a small canoe or other type boat with a small outboard and spike out with it as many others do. Some even tow a small raft or jon boat and even fill them with fuel.

    You will see and learn much on this trip.

    Take extra nuts and bolts and a spare key or 2 for your jet,, those tiny parts are easy to drop while changing out on the water.



    transom mod.





    One last tip, buy an extra water pump and housing and install it on the pump, saves time and you don't have to worry about damaging your impeller changing it back and worth.

    Good Luck

    Steve
    "I refuse to let the things I can't do stop me from doing the things I can"
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    Default looks like new!

    Quote Originally Posted by stid2677 View Post
    I found that I could get by with 5 inches of lift travel


    I don't understand how it is that you have a lift (so you must go some skinny water places) and yet you don't have so much as a scratch on your lower end unit?

    And no prop protector? Or are those only for the smaller motors, like mine?

    Even though I've still never yet broken the seal on my lower end unit, I have lost a considerable amount of paint from it, and plus dinged the holy heck out of my mac's river runner prop protector, not to mention polishing a few props down to a smaller size....

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    Quote Originally Posted by FamilyMan View Post
    I don't understand how it is that you have a lift (so you must go some skinny water places) and yet you don't have so much as a scratch on your lower end unit?

    And no prop protector? Or are those only for the smaller motors, like mine?

    Even though I've still never yet broken the seal on my lower end unit, I have lost a considerable amount of paint from it, and plus dinged the holy heck out of my mac's river runner prop protector, not to mention polishing a few props down to a smaller size....

    LOL, those pics were taken when it was new. Bent the skag on the first trip, I should say my buddy bent the skag after he dropped me off to kill a bear. It now has a scuffed up stainless steel skag protector on it. Use the prop mostly in the salt.

    Steve
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    Outboard Jet manufactures an adjustable outboard mount that allows the engine to be moved up and down to accommodate jet or prop bottom ends. It looks similar to a power plate but uses 4 bolts to set the height and is a snap to work with. I'm not interested in power operation, just the 5"+ of adjustability.

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    Thanks for the tips. I have done this trip many times, but we now like running from Nenana vs.the bridge. Last year I ran a jetboat, this year taking my Hewes, the jet is only going to be used if the water drops out before we get back to Nenana, last year it was floating ice and dropping fast when we returned. I am bringing my scanoe and 2hp honda again,as well as my BIL will be in his predator s.j. for when we are hunting skinny spots. I am hoping the test run will go good as I will only have 4 days between getting off of work and heading north!

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    Default Now THAT makes more sense, thanks!

    Quote Originally Posted by stid2677 View Post
    LOL, those pics were taken when it was new. Bent the skag on the first trip, I should say my buddy bent the skag after he dropped me off to kill a bear. It now has a scuffed up stainless steel skag protector on it. Use the prop mostly in the salt.

    Steve
    Sorry to nitpick, but it just didn't make sense to me; now it does. Thanks, and tell your buddy thanks, for scuffing up your lower end all proper like! It just didn't look right, all pristine like. That ain't the Alaskan way.

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