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Thread: Lower Prop Unit

  1. #1
    Member Stanly's Avatar
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    Default Lower Prop Unit

    Took my 22' SeaArk to Valdez this past weekend. Have an Yamaha 80 Jet. Bought the boat new last year. I have a couple of questions, I have not done any research yet, but know this is "THE" place to go for good info. I seemed to always be picking up sea vegetation down there and it had a major effect on my motors performance. Do you know how much new/used lower prop units run (ballpark) and how hard are they to swap out? Is it something you can do in your garage or do you need special tools etc...Thanks in advance!

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    Member SusitnaAk's Avatar
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    How bad you want it, how much are they willing to sell, Can,t help with the price no idea there. But if good with a wrench not hard to do 1st time always the tuffest, I would ask about the transom height though, There could be some differences, And can be made up with brackets you can buy.

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    Member MARV1's Avatar
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    Lower prop units run about $1200 at a dealership, some places more though. Can find a used one for cheaper, 80/100 4-strokes are the same.
    The emphasis is on accuracy, not power!

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    Member MARV1's Avatar
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    Oh, and doesn't take long to swap out if you know how to do it. The lower unit just goes right in place with 6 bolts total.
    The emphasis is on accuracy, not power!

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    Member Akgramps's Avatar
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    You will need to lower the motor 5"-6" to get the correct height for the prop, so if you have a 115/80 Yam 4 stroke that ~ 420 pounds to wrestle up and down again, do you have a power lift/ trim? Anyway you can use that as a aid to slide the motor up and down on the transom. or you can use a lift (jack plate) which will give you this adjustment either manually or via a switch. the lift will set the motor back from the transom some distance and while that arrangemnet will not hurt your performance when operating with a prop, it could compromise your jet performance some.
    Lower units price can vary considerably depending on brand, good thing is there a ton of Yamahas out there. If you decide to make the swap. suggest picking up a secong water pump which will eliminate having to swap that as well.

  6. #6
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    PowerTrans jackplate will help you a great deal. It has 7.5 inches of vertical lift.

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    Member Dupont Spinner's Avatar
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    Or you could get a 5 inch extension to go between the lower and upper.

    20 minutes to go from prop to jet...35 to 40 minutes from jet to prop.

  8. #8
    Member Stanly's Avatar
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    Default I called

    Dewy's, they sell a new lower unit for $1,225 plus another $40 for hardware. My boat has an adjustable plate. Does anyone know where to get a used unit? Are they easy to come by etc...? I'm pretty convinced I have to have one, I don't need to be out and have issues with getting stuck somewhere due to crap floating in the water. Thanks again for the help!!

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    Member Akgramps's Avatar
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    Yeah, forgot about them, they are called "Bay extensions"

    Below is link and they do have some Yamaha units, and the good part is you dont have to move the motor back......

    http://www.marineparts.com/PARTSPAGE...ories/ACC8.HTM

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    Member Akgramps's Avatar
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    Try a wanted ad on craigslist or search craigs

  11. #11
    Member Dupont Spinner's Avatar
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    I found one for Tblooma, used, off Ebay for 289 shipped.

    His river sled, Woolridge, is a jet sled with that prop, but it doesn't like the chop. I am hearing something about suspension seats are in his future. It looks like I will be hunting Ebay again for him.

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    DO NOT INFLICT UPON YOURSELF THE PAIN OF A MANUAL TRANSOM JACK! Unless you are a masochist. I know, I had one. Also, using the power jackplates you have to be VERY careful to find one that has better than 5.5 inches travel. Speaking of experince with Johnson and Evinrude motors. The difference between the prop and jet and getting the adjustment correct is roughly 3/4". Now that doesn't seem like much. All you have to do to see with you own eyes what this adjustment means is to lower your jet so the leading edge of the foot is 3/4" under the straightline waterflow from the bottom of the hull. Lots of drag, and tremendous shower of water into the air and back of the boat. I had to have a custom extension weldd up that I bolted to the top of my CMC jackplate. It was a b!tch switching back and forth. You have to find a jackplate that will allow you the greater adjustment height to make the conversion painless. Unfortunately there are none made that are affordable. The highest lift plate I have found in years of internet searching is Bob's Custom Marine, it is 6", and has been out only a couple years. There is one outfit in Florida that has a parallelogram arrangement that will lift 17" to 24" but they want $2.5k for the lift, and it has a two-foot set-back that is just a lever to bend your transom. CMC used to make an 8" lift, but quit making them years ago. I called them last year to ask if they'd build me one from spare parts, but the fellow said no. So there you are.

    If Snowolfe would post the link to the PowerTans jackplate, I'd like to see it because I wasn't able to find it after 1/2 hour of searching.

    www.cook-mfg.com
    www.portaproducts.com
    http://www.thmarine.com/category.cfm?CID=43&CHID=1
    Great spirits have always found violent opposition from mediocre minds. The latter cannot understand it when a man does not thoughtlessly submit to hereditary prejudices but honestly and courageously uses his intelligence. Albert Einstein

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  13. #13
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    Here you go:
    http://www.powrtran.com/cgi-bin/cart...?parts_id=9662

    I could not find it myself untill I realized it was spelled Powrtran. My mistake. Sea Marita installed it on my Wooldridge. Believe the price was $899. My only complaint is it does not have a gauge to measure the lift.
    I have only used this boat a couple of hours so far this year as it was built for moose hunting so I can offer a better report upon my return. It should prove to be advantegous as I can raise the motor after getting on step and allow me to run a little more shallow and hopefully improve my fuel economy. But the main reason I had the lift installed was because I want to add a jet pump next year as my finances permit.

    The owner of the company told me he visited a handful of marine dealers in Alaska asking them what they needed in a lift and this is why he went with 7.5 inches.
    If you live close to Eagle River you can swing by and take a look at it as we do not leave until Wed.

  14. #14
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    Well there it is!! So someone does actually make one. I am going to have to telephone them tomorrow and have some info sent to me. Thanks for the link. Years of frustration have just evaporated. Wow!

    Thanks again.

    Ok, getting back to the jet and lower unit. On my Evinrude 90 h.p. it took about 30 minutes to make the switch, and that was just me. On my Johnson 175 h.p., that took about an hour with just myself. The jet pump went from 50 pounds to near 100, so it was a pain. And there was the little rubber puck to seal off the gear control tube.
    With that 7.5 inch lift, the possibilities are now endless.

    I know I spent many hours at the back of my boat, with boat the 90 and 175 adjusting the motor to the plate, plate to the transom, ect. All that was needed was that additional 3/4".

    Good to go now!
    Great spirits have always found violent opposition from mediocre minds. The latter cannot understand it when a man does not thoughtlessly submit to hereditary prejudices but honestly and courageously uses his intelligence. Albert Einstein

    Better living through chemistry (I'm a chemist)

    You can piddle with the puppies, or run with the wolves...

  15. #15
    Moderator stid2677's Avatar
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    Did this jet to prop mod on my Wooly last year. Check out the thread.
    Go with the electric lift and a water pump on each unit.
    http://forums.outdoorsdirectory.com/...ad.php?t=12357

    Steve
    "I refuse to let the things I can't do stop me from doing the things I can"
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