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The KBW10 is a VERY robust transmission. However these old Kanzaki transmissions do not tolerate engine to shaft misalignment nor shifting lever misalignment. They also need to have their fluid changed out on a routine basis, the same interval as when you change your engine oil.

Look on the ID top plate of the trans. to see EXACTLY which fluid is needed - will either be ATF or 30 weight oil. DRAIN the old fluid, using the drain plug under the output shaft, dont just 'suck it out with a vacuum source' as draining will remove the free floating metal particles. Many of these older Kanzaki's also have a 'strainer' which needs to be cleaned each and every time you change the oil - the strainer catches free metal particles and pieces of the friction material that comes loose. The strainer protects the internal OIL PUMP that feeds the upper bearings inside the transmission!!!!! If the strainer is not routinely cleaned, little oil will get to the upper bearings, etc.

To check for shifting alignment: shift into neutral, remove the pin from the shifting lever clevis ON the transmission, remove the pin and clevis ----- there should be NO binding when removing and the pin MUST come out easily OR you need to readjust the linkage. Then shift into forward and test the pin into the linkage, and then again when in reverse. Adjust as necessary. This shifting alignment at the lever on top of the trans. probably should be verified each and every time you change the trans. fluid.

These Kanzaki transmissions automatically adjusts the internal gear shifting and gear running clearances based on rpm of the gears and oil pressure developed by the pump ----- but IF AND ONLY IF the shifting lever and its connecting PIN are not binding and the OIL PUMP is getting sufficient oil/fluid.

If this isnt making sense, Id suggest that you go to your local Yanmar distributor and get a copy of the Yanmar Service Manual for the 2QM20(H)/3QM30(H) for detailed instructions on how to (regularly) check the adjustments on these transmissions. Dont do this and you can expect a $2000 repair bill for a complete 'rebuild' ... if you remove/reinstall the engine/transmission yourself; extra labor charges if you have this done.

Now that I have your undivided attention .... ALSO check your engine alignment and the condition of your cutless bearing as these can also cause such 'whining'. The Kanzaki's require NO MORE than 0.001" engine/transmission to propshaft misalignement when measured at the face of the transmission output flange and the coupler/flange on the prop shaft when measured with 'feeler gauges'.
Also, Yanmar engine mounts on these heavy old 2QM and 3QM 'should' be changed out every 5 years !!!!!! , they 'sag' over time and cause engine misalignment .... and that can set off a serial chain of events that can seriously harm the transmission. This natural engine 'mount sagging' happens whether the engine is run or not - change out these mounts solely based on AGE.

hope this helps ... hope you find that the problem is MINOR. ;-)
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