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  1. #1
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    Lower Unit / Prop Issues

    '08 Ranger Z520
    '08 Evinrude ETEC 250 HO
    Model E250DHLSCS
    Prop: 3 blade, 14-1/2" x 24", Raker II prop with three 5/8" vent holes (Note: ~Prop to Pad height = 5" w/ 6" hyd. jack plate down)

    I just replaced my '08 Lightening lower unit with the M/2 gear case. Then the existing 24" prop would cavitate and spin out when trying to get on plane if exceeding 4500 rpm's. This was never an issue with this prop on the Lightening gear case. Therefore, I proceeded with the following 26" & 24" Prop Trials:

    The 26" Raker II w/ (3) 3/8" vent holes got on plane in 5 sec, and ran 68 mph at 5800 rpm's. VERY HIGH torque at higher speeds (Very Hard to turn left). This M/2 has no torque tab, only a flat plate. Thoughts?


    The 24" Raker II w/ (3) 5/8" vent holes, with 1 vent hole plugged, got on plane in 4 sec, and ran 63 mph while holding at 6000 rpm's. Likely could have run at 6200-6300 rpm's, yet BRP recommended maximum is 6000. Fairly high torque at higher speeds. Lost second plug or would have tried plugging 2 vent holes. Could plugging 2 vent holes increase top end and/or reduce maximum rpm's, vs plugging only one vent hole?

    Any knowledgable feedback appreciated!

  2. Member
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    #2
    Quick question while we wait on the gurus to chime in. Did you have the steering torque with the L2 gearcase?

  3. Member
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    #3
    Quote Originally Posted by yandeltx View Post
    Quick question while we wait on the gurus to chime in. Did you have the steering torque with the L2 gearcase?
    No torque tab before with L2 either. So I did have some steering torque before, but this M/2 with the 26” is MUCH harder to turn left at speed.
    Last edited by tbng381; 09-23-2020 at 12:03 PM.

  4. Pat Goff
    Join Date
    Jun 2004
    Location
    Seadrift TX
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    #4
    Simple answer is you’re too high. Big prop torque and very high prop slip are symptoms.
    Pat Goff

    Two degrees from center
    of nowhere.
    Smithwick TX.

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  5. Member
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    #5
    Ok thanks. I was running with the jack plate all the way down, but had trimmed up quite a bit to where I usually run and where it seemed to be running good up on step. Yet it was Very Hard to turn left. I can try again trimming down some.

  6. Pat Goff
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    Jun 2004
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    #6
    You might need to reset your motor on the plate. But that is based on things we can’t see. You might have something sticking down in the water that would cause the same issue.
    Pat Goff

    Two degrees from center
    of nowhere.
    Smithwick TX.

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  7. Member
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    #7
    Thanks. I have a hydraulic jack plate so I can raise it more and give it a try without trimming as much. Yet I believe I tried some of that. Would adding a torque tab help significantly?
    Last edited by tbng381; 09-23-2020 at 12:09 PM.

  8. Pat Goff
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    #8
    Torque tabs work great.
    But if you need them you’re not setup right
    Pat Goff

    Two degrees from center
    of nowhere.
    Smithwick TX.

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  9. Member
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    Red Oak Va.
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    #9
    That M2 gear case caused a lot of people to lose speed usually 5 mph.

  10. Member
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    #10
    Thanks. For an update, I plugged all the vent holes in the 24” prop . Good hole shot yet still over revving up to 6300 rpm at only 63 mph. Backed off to 6000 rpm (max recommended) with 60 mph. Plan to weld vent holes closed and re-pitch to a 25”.
    Then tried a 26” prop and ran 5800 rpm at 67 mph, then quickly spun the prop or hub.
    Learned the exhaust overheated through the prop and that heat caused spinning of the hub or prop. Plan to evaluate exhaust and water throughput in an effort to prevent overheating and to achieve proper cooling.

  11. Member
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    #11
    They make rubber hubs that will take the extra heat and you can get the right trim tab for that motor that has the hole in it to put extra water into the exhaust and cool it down. Simplest way to stop that is to get a 25" tempest with the right hub kit for an E-tec

  12. Member
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    #12
    Thanks. I plan to add that torque tab with water passage. I’ll check into that hub.

  13. Member
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    Sanford NC
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    #13
    If you have hydraulic steering, there will be no trim tab just flat cover, if you remove you will experience overheating at slow speeds.
    Comanche20 (Don)
    2008 Ranger Z 20, 225 RUDE
    Ultrex 45/36/112
    2 Birds
    2020 F150 LIMITED Eco Boost

  14. Member
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    #14
    Quote Originally Posted by Commanche20 View Post
    If you have hydraulic steering, there will be no trim tab just flat cover, if you remove you will experience overheating at slow speeds.
    Thanks. I’m just now seeing this response. Will over heating occur at slow speeds even if the flat plate is replaced with a torque tab having a water port hole?

  15. Member
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    Marietta, Ga
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    #15
    Well i just thought I would post about some of my experience with my old boat. (201 status w/2005 Evinrude etec) One problem I had when I switched to a Evinrude M case lower unit was that it would run good with a 4 blade prop with the weed ring installed, but when I switched to a 3 blade prop it was very hard to get out of the hole without the prop blowing out. The cure was installing a 3 blade prop seal That is much like the 4 blade weed guard but must be used for the magnum case because of its slightly larger case size. (3 blade prop seal part#0346462).
    Another problem i had after the Evinrude magnum case lower unit went out, I replaced it with a aftermarket SEI lower unit (Chinese made I believe). I believe they called it a Magnum 2 case but it was smaller in diameter than the Evinrude Magnum case and did not require the 3 blade ring. Then I started burning up prop hubs with any constant speed above about 5k rpm. This-would also Damage the prop seal from excessive heat. After much trial and error I finally found out the cooling system was not putting enough water in the exhaust thru the hub to keep it cool with this lower unit. The fix ended being a retro-fit kit from Evinrude that puts more water flow into the exhaust. Real simple install and cost I believe about 30 dollars. I don’t know if any of this applies to your problem but I thought i would share my experience.

  16. Member
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    #16
    Thanks for the information. Great to know. I’ll definitely look into how this may apply in my case.