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Thread: School me on jet units....

  1. #1

    Default School me on jet units....

    I haven`t run a search yet but may get the time tomorrow night.

    Anywho, I have a pump for my 115 Merc that is mounted on a 18' Achilles.

    I have no experience with outboard jets and have never worked on a pump.

    Took a look at the sleeve and it has some good-sized grooves but enough material at the bottom to match the impeller. The impeller is aluminum and has some decent sized dents in the leading edge. The grate also has some fairly bent fins that look to be about an inch in the worst spots.

    Questions...

    1) Will the aluminum impeller get me enough performance considering the loaded boat will never exceed 2K pounds?

    2) Is a stainless unit just overkill for 2-3 trips a year in this application?

    3) Would it be best to file the impeller, get a new sleeve, get someone to shim it and call it good?

    4) Pull the grate and just hammer the fins flat or replace?

    5) Roughly how shallow do I dare go with this thing? I`m told it will do 30mph on the pump.

    Any thoughts or suggestions are welcome and appreciated.

  2. #2
    Member SusitnaAk's Avatar
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    Default Jet

    #1Yes we used to fig about 20lbs per Hp.
    #2 two to three could be, but they are the best at taking abuse
    #3Yes, yes yes,
    #4Pull Two long pins, Drop out the grates Remember what way they go, go to town on it with hammer they are soft medal
    #5 6 In, or so on the straight, no turns, She will dip a bit in the corners, Also you are running and intertube, They don,t get along well with rock,s or sticks.
    I would support it ,the motor, that is, when towing to your spot,That is alot of engine yanking on the transom going down the road.

  3. #3

    Default

    Quote Originally Posted by AK2AZ View Post
    I haven`t run a search yet but may get the time tomorrow night.

    Anywho, I have a pump for my 115 Merc that is mounted on a 18' Achilles.

    I have no experience with outboard jets and have never worked on a pump.

    Took a look at the sleeve and it has some good-sized grooves but enough material at the bottom to match the impeller. The impeller is aluminum and has some decent sized dents in the leading edge. The grate also has some fairly bent fins that look to be about an inch in the worst spots.

    Questions...


    1) Will the aluminum impeller get me enough performance considering the loaded boat will never exceed 2K pounds?

    2) Is a stainless unit just overkill for 2-3 trips a year in this application?

    3) Would it be best to file the impeller, get a new sleeve, get someone to shim it and call it good?

    4) Pull the grate and just hammer the fins flat or replace?

    5) Roughly how shallow do I dare go with this thing? I`m told it will do 30mph on the pump.

    Any thoughts or suggestions are welcome and appreciated.
    Answers,

    A 115 Merc sounds like a lot of motor for an inflatable - that is if I have the picture of your boat in my mind right. But with that said, square up and straighten up the leading edge of the impellor with file, If not toss it. Or, if you are not pressed for time, take to a prop shop to get fixed, it's cheaper. Also, throw away the sleeve if you can't shim it so its tight - tight meaning that just barely more than a regular old sheet of paper easily slides right in, and so it is not touching anything. Don't worry about the grooves in the sleeve, they don't seem to impact the efficiency much, if at all. Stainless will be a waste of money in my opinion as with that light load you are going to hop right up on step in about the length of the boat. Go ahead and hammer the fins straight, it won't hurt a thing as long as they still fit tightly. As far as how shallow, I get nervous in my zodiak (20 hp at the pump) in less than 8 inches of water as I worry about all the banging and a transom that is merely glued into the boat.

  4. #4

    Default

    Quote Originally Posted by T.R. Bauer View Post
    Answers,

    A 115 Merc sounds like a lot of motor for an inflatable - that is if I have the picture of your boat in my mind right. But with that said, square up and straighten up the leading edge of the impellor with file, If not toss it. Or, if you are not pressed for time, take to a prop shop to get fixed, it's cheaper. Also, throw away the sleeve if you can't shim it so its tight - tight meaning that just barely more than a regular old sheet of paper easily slides right in, and so it is not touching anything. Don't worry about the grooves in the sleeve, they don't seem to impact the efficiency much, if at all. Stainless will be a waste of money in my opinion as with that light load you are going to hop right up on step in about the length of the boat. Go ahead and hammer the fins straight, it won't hurt a thing as long as they still fit tightly. As far as how shallow, I get nervous in my zodiak (20 hp at the pump) in less than 8 inches of water as I worry about all the banging and a transom that is merely glued into the boat.
    The boat in question...





    I`ve spoken with someone else that has one that is powered the same but runs an Optimax 115 and is doing good with it. I intend to re-power in the 70-90 class 4-stroke next year and sell the 2-stroke with prop/jet. I personally don`t get muc of a thrill running the rivers and like you said I worry about strikes on a rubber duckie.

  5. #5

    Default

    Quote Originally Posted by SusitnaAk View Post
    #1Yes we used to fig about 20lbs per Hp.
    #2 two to three could be, but they are the best at taking abuse
    #3Yes, yes yes,
    #4Pull Two long pins, Drop out the grates Remember what way they go, go to town on it with hammer they are soft medal
    #5 6 In, or so on the straight, no turns, She will dip a bit in the corners, Also you are running and intertube, They don,t get along well with rock,s or sticks.
    I would support it ,the motor, that is, when towing to your spot,That is alot of engine yanking on the transom going down the road.
    Not running inner tubes however this is the commercial version w/7 layers and has 1/8" hypalon skins under the tubes.

    Working on getting the transom on the bunks this afternoon...we`ll lift it with the forklift and set the trailer/boat correctly and will also get a transom saver installed.

  6. #6

    Default

    Quote Originally Posted by AK2AZ View Post
    The boat in question...





    I`ve spoken with someone else that has one that is powered the same but runs an Optimax 115 and is doing good with it. I intend to re-power in the 70-90 class 4-stroke next year and sell the 2-stroke with prop/jet. I personally don`t get muc of a thrill running the rivers and like you said I worry about strikes on a rubber duckie.
    That is SWEET!!!

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