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Thread: Yanmar SD50 Sail Drive Slipping

  1. #41
    Join Date
    Jul 2009
    Big Pine Key Fl

    Default Re: Yanmar SD50 Sail Drive Slipping

    Quote Originally Posted by telecam View Post
    So, here is the latest on my SD-50 saildrive slipping in FWD. Prop and prop hub were replaced and that did not fix it. As I initially expected, the Yanmar SD-50 cone clutch was glazed and needed to be serviced. That is with just over 200 hrs on the engine.... I talked to Yanmar guys at the Annapolis Boat Show yesterday and when I mentioned SD-50, they all looked up in dismay... They say Yanmar maintenance schedule recommends that SD-50s cone clutches be inspected every 250hrs. In reading the maintenance manual, I actually see that this comes at every 500hrs, not 250hrs. In any case, there is obviously major flows with the SD-50s clutch design and reliability and Yanmar's own people acknowledge it. I think Yanmar owes all SD-50 owners a clear explanation of what the weakness are and a fair settlement in either retrofitting those sail drives or providing regular checks and service free of charge. I found it unacceptable that I am asked to get my clutch taken apart every 250 hrs for inspection, don't you?
    It make me not wanting to have anything to do with them!

  2. #42
    Join Date
    Sep 2009
    on the boat

    Default Re: Yanmar SD50 & SD40 Sail Drive Slipping and Leaking Oil at Motor. Problem Solved

    Some feedback on my very old post where we identified the cause of the Slipping Cone Clutch problem. Just a quick re-cap:

    The problem originates when wear set in on the Copper Thrust Washers used below the Top Nut and the Lower Collar, causing increased up/down free play on the Vertical Shaft. This free play, combined with the limited Selector Lever travel, causes the Selector to retract BEFORE the (male) Cone makes firm contact with the (female) Cup.
    This sometimes results in partial contact with some drive (but not the full thrust) of the propeller, which if not noticed quickly ruins the Cone due to slipping/friction. This more oftens happens in Fwd with LH propellers, which requires the Vertical Shaft to lift/rotate upwards along the Helical Spline untill the Lower Thrust Washer bottoms out.

    This all sounds very technical, but in a nutshell, it is the cause of the Slipping Cone problem.

    The problem is aggravated by Yanmar using Copper Thrust Washers with thickness increments of 0,5mm. This is too much, resulting in an assembly with a lot of up/down free play even before wear sets in!

    I also looked at, and have experience with the VOLVO drives operating on the same principle as Yanmar ( but without the slipping clutch issue).
    Volvo uses Thrust Bearings, (Not Thrust Washers) allowing much closer initial setting up tolerances, and reduced wear.

    I have developed a Cone Clutch Upgrade Kit for both the SD40 and SD50, based on using THRUST BEARINGS in place of the Washers, as well as an Adjustable SET SCREW and Lock Nut on the Selector. Allowing closer inital setting up tolerance, and reduced wear.


    The Kit consist of a bigger diameter Lower Collar and Top Nut (with more surface area), Thrust Bearings, Selector Set Screw and Lock Nut and a 10mm Brass Barb fitting and hose/end filter assembly to allow an "Open" breathing situation.

    The standard Yanmar closed saildrive does not allow for the expansion of the oil inside the drive when heating up, especially with mineral oil rather than synthetic oil is used. This is is aggravated when water has entered through the Propeller Seal, when heating up, causing more expansion.
    The "Open" breathing installation prevents pressure from building up due to heat generated when the drive is used at high power, resulting in the Engine Seal blowing oil out into the engine room and or the Prop Seal leaking oil.
    The "open" breathing also reduces the possibility of water entering the Prop Seal when the drive cools down after operating at a high power.

    I have both my drives in my 2010 V500 upgraded and with 2000Hrs all still good!!

    Quote Originally Posted by RobV440 View Post
    Does anyone know if you have to remove the engine from the sail drive to replace the cone clutches? My V440 has 850 hours and is starting to slip in forward some times. Very unnerving when pulling up to the gas dock.

    Dream Maker V440

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