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I’m sure it can be said that all engines have their own issues. Our last few years have been spent learning the ins and outs of outboard engines. While that info is still important as we will have a Yamaha outboard powering our tender, the Leopard that we’ll be living and working on has an entirely different setup for its auxiliary engines.

In the stern of each hull of the 4600 lies a 54HP Yanmar diesel engine. Unlike some of this boat’s Leopard predecessors, the engine is not connected directly to the propellor via a straight shaft. On the contrary, it transfers power through a couple of right angles via a system called a saildrive. On the 4600, the particular model of saildrive is a SD50, a piece of gear not unknown to have issues.

A SD50 saildrive

I have had the good fortune to be exposed to some of these issues because our friends Kirk and Donna have the exact same engines and saildrives on their Lagoon catamaran, Ainulindale. I have witnessed first hand some of their woes and the steps that they have had to take to rectify them. One particular issue relates to leaking seals on the saildrive, quite possibly the result of overfilling the gear oil chamber. How could that possibly happen? Quite easily actually.

It seems that most of the SD50s out there have a dipstick with incorrect markings for the high and low gear oil levels. While this info was made known to the dealers via a service bulletin, I’m not so sure it has filtered down to all of the users. Fortunately for us, Kirk did find out about this. The photo below is of the new, properly-marked gear oil dipsticks. Each one costs less than $10.00 and having them can help to avoid seriously costly engine drama. Big thanks to our buddy Kirk for sharing this info and for picking us up two of the dipsticks for the new boat.

The new properly-marked dipsticks.

If you have an SD50, you might want to look into this. I have been told that the new dipsticks are all marked with a dot on the top made by a back sharpie marker. If your dipsticks are missing that dot, you might want to follow up on this.


  1. Man, is that ever bush league. They should be sending replacements properly marked to all owners and hope they don’t get a class action for all the bills people had getting their sail drive fixed.

    Marked with a sharpie…. Wow.

  2. Hi ZTC!

    Wow, I love your blog, thank you for the great education. You have taught me a lot.

    Thanks for the note on the dip stick, I am going to look into that asap.

    We have a SD50 on our Oceanis 45. Additionally we have a 4 blade Maxprop Classic II hanging off of it. The performance of this setup is fantastic but it comes with significant maintenance cycle.

    Some hints/issues I have seen: (sorry, not well organized and you likely already know most of this)
    + We burn through a SD anode set every four months, ouch. And the anodes are not cheap, $40 per set. I think the zinc version lasts a bit longer than the Aluminum version.
    + In order to change the anode without taking the prop off you need a split ring adapter, I bought mine here
    + I have changed the lube once myself while the boat was still in the water. Wow, what a pain that is. I used the push / pull method noted in the SD50 manual. The 90 weight lube is thick thick! (Quicksilver HP 90).
    + For pulling old lube out: I used an electric dinghy pump attached to the oil fitting to blow out the lube while at the same time use the Yanmar hand pump (28210-000081) to pull it out.
    + For pushing new lube in: I initially bought the Yanmar (28210-000081) oil pump but it leaked horribly, huge mess. I have since purchased the but have not tried it yet. I use my electric pump to pull the lube from the other end of the unit.
    + Here is the part number for the lube fitting Yanmar (196311-92960)

  3. At the Annapolis boat show we went to a diesel class that talked about a class for Yanmar that teaches you how to tear it down and rebuild it. We could probably get some information for you if you want.

  4. Is the oil checked with the dipstick screwed in or not? I can’t seem to get a straight answer from a Yanmar dealer.
    Anybody know for sure?

    • Great question. I don’t know but maybe Kirk has found out.

      • The owner’s manual for the SD50 specifies that the dipstick NOT be screwed in. The revision to the dipstick length in 2009 did not change that directive. While we have received conflictiong instructions from varios “mechanics” we have been assured by Yanmar (Mack Boring) that the owner’s manual instructions are to be followed. Further, we have always understood that oil reading dipsticks that are secured by threading in are to be measured without screwing in. And as a final note, the HIGH level mark on the new, longer dipstick corresponds to the LOW level mark on the older, short (incorrect) dipstick. The change was made as a result of the shorter dipstick leading to a higher ovrfill fluid level that resulted in a smaller expansion air space at the top of the chamber. The smaller expansion space resulted in higher operating pressures causing the unit seals to “pop” or reverse, resulting in increased warranty claims. The operating pressure is effectively lowered with the lower fluid level and corresponding increased expansion chamber size. Since the thread dimension is approximately the same distance as the change, one could have threaded the old short dipstick in to measure the level and keep a reasonable correct level, however, that practice could obviously lead to errors. Threading the new longer dipstick in to check the level would likely result in an under fill.
        Sorry for the technical dissertation.

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