Results 1 to 7 of 7

Thread: Propellers.....Help.....!!!

  1. #1
    Join Date
    Mar 2000
    Posts
    202
    Rep Power
    25

    Talking Propellers.....Help.....!!!

    RE: 1990 18 2+3
    Merc 350 260 HP

    Propeller performance so far:

    Mercury Black Max propeller

    14 x 21 4000 rpm’s = 47 mph
    14 x 19 4400 rpm’s = 45 mph

    I can’t believe my speed went DOWN !!

    Any suggestions??

    A friend is suggesting I try his Land & Sea variable pitch propeller 14 x 12-22.
    Any thoughts ?

    Will a propeller off an OMC King Cobra fit my Alpha ?

    I feel I should be able to achieve between 55 to 60 mph with my setup. Isn’t that very reasonable !!


    Stan


  2. #2
    Join Date
    Mar 2000
    Posts
    1,556
    Rep Power
    26

    Post

    Stan, I ran your numbers; assuming a 1:50 gear ratio; on the computer http://www.boatramp.com/prop_applet/...erAppletG.html The number add up. Approx. 12 to 13% slip. I think an 18 with an Alpha and 260hp should run 55 to 60mph!!. Are you trimming the outdrive up, to loosen the hull?
    GEOO
    " Sometimes the object of the journey is not the end, but the journey itself "

  3. #3
    Join Date
    Mar 2000
    Posts
    202
    Rep Power
    25

    Cool

    Yes, I probably need to learn to work my trim better. The engine is rated 4200-4600 rpm. I think the Thunderbolt V ignition system has a rev limiter built in. Can that be changed ? Will that be bad for my engine ?

    More Questions:

    Do I need more rpm’s to achieve the speed I want ?

    Do I need a different prop ? ( Obviously ) What prop ?

    I am about to try a Torque-Shifter prop and thoughts ?

    Will a 4-barrel carb help the situation?

    The list goes on and on……

    Stan

  4. #4
    Join Date
    Mar 2000
    Posts
    1,556
    Rep Power
    26

    Post

    Stan,

    I tried Land and Sea Torque shifting prop. Great for water skiing did not gain top speed.
    The props you have seam to be working correctly; Speed vs slip vs rpm's.
    Donzi's run slow unless you trim the bow up alot at full thottle. Is your engine fresh?? You should be able to hit 55mph GEOO
    " Sometimes the object of the journey is not the end, but the journey itself "

  5. #5
    Join Date
    Mar 2000
    Posts
    1,542
    Rep Power
    26

    Cool

    Stan,
    Here is my 2 cents about the Torque-Shift prop.
    They tell you when you buy the prop that "THIS IS NOT A SURFACE PIERCING PROP" they aren't kidding. while testing his brand new prop my freind gets his boat on plane,(pulls great!!!) then feels the shift (just like you're supposed to) reaches 40...50...trims it out a little, 55...60..wow this thing looks like it's going to work great!!! 65...trim it little more and BA-BLAM oops... what was that?!!!
    we stop the boat, raise the motor,and inspect the $600 investment "well at least we still have 1 blade left". It's a good thing that we were going up river.
    Don't get me wrong I'm sure it's a great product. Just be carefull.
    BERTRAM BOY
    ------------------------
    Charter member KWOSG

  6. #6
    Join Date
    Mar 2000
    Posts
    2,593
    Rep Power
    27

    Post

    Stan,
    I have a 96 18 2+3, 350 2-barrel, 210 or 215 hp, 14X19 Quicksilver prop. At 3700 ft elevation at WOT, drive trimed down I'm close to the speed and RPM you list for the 19 pitch, maybe a little more speed though. With drive trimed all the way up though, RPM's peak at 4600 and speed is 54 MPH (speedo).
    RickS-E

  7. #7
    Join Date
    Mar 2000
    Posts
    202
    Rep Power
    25

    Post

    Rick,

    Your HP should be 260 with the 350 2- barrel

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •