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Trolling/slow speed drive/maneuvering ZF Gears

Discussion in 'Engines' started by Capt Maritime, Jun 19, 2022.

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  1. Copacetic, May 11, 2026 at 12:31 PM
    #21
    Copacetic

    Copacetic New Member

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    Mar 5, 2026
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    Location:
    Homer AK
    Does anyone have experience with Yanmar 6LY2-STE (420 hp) with single-speed ZF gears. Currently have the two-speed units but need replacing. Will the single-speed units get down to 2 kts using troll valves. Typically I am in low gear in troll mode to get below 2 kts now.
  2. Capt Ralph, May 11, 2026 at 3:17 PM
    #22
    Capt Ralph

    Capt Ralph Senior Member

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    Ouch, Not much of that stuff out there.

    It's all in the ratios, shaft speed & prop size.
    None of that data was provided for us to even guess (SWAG) about.

    I do recommend you find this data and go to a real ZF shop AND a real Prop shop and inquire.

    You may end up just dragging a bucket (drogue) on one engine to keep 2kts.
  3. ranger58sb, May 12, 2026 at 7:19 AM
    #23
    ranger58sb

    ranger58sb Senior member

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    Location:
    Chesapeake Bay, USA
    No experience with larger Yanmar diesels...

    But previous boat, we had Cummins 450s and ZF 280-1 A gears with trolling valves (mechanical control) -- and we could get speeds down to about 1 kt running on only one engine. Presume these are an example of what you're calling "single speed."

    Local trolling routine is generally between 2.5-3.5 kts and we could do that easily enough, too, usually on one engine alone but occasionally with both running due to some combination of wind and tide impacting steerage.

    -Chris
  4. DOCKMASTER, May 13, 2026 at 11:28 AM
    #24
    DOCKMASTER

    DOCKMASTER Senior Member

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    Ketchikan, Alaska
    The engine should have no impact on trolling valves as they are tied to the gears only. Single speed or two speed shouldn't matter either. The trolling valves simply reduce clutch pressure significantly and allow the clutch to basically slip. Do your engines have a slow idle mode? If yes, can you use it for extended troll periods? Even if you have no slow idle mode, are your engines OK to idle for extended troll periods? I assume it's not an issue so long as you run them up to full cruise for a bit after trolling.

    The two things you need to confirm are: 1) Can you get trolling valves for the gears you intend to install? 2) what will you use to control the valves? Do your current engine controls have that feature? If not, you are looking at new controls.
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