By Andrew Spaulding
Most of us put the transmission in reverse while sailing to lock the propeller shaft from turning. On some boats this works fine for many years. However, on some boats this behavior can damage the transmission. Whether or not sailing with the transmission in gear will damage your drive train is dependent on what kind of transmission and propeller you have. We will review a Yanmar technical bulletin to get the official word from one manufacturer. This information applies to mechanical marine gear transmissions and saildrives only.
The first kind of mechanical transmission that we will discuss is one with a cone clutch. Cone clutch transmissions are highly susceptible to damage when left in gear while sailing. The cone slippage will be introduced which will void the warranty. There is also the possibility that the cones won’t disengage, making it impossible to shift the transmission out of reverse. With a fixed propeller, the transmission should be in neutral, which will allow the propeller shaft to turn. With folding or feathering propellers, put the transmission into reverse to fold or feather the propeller, and then put it into neutral.
The other types of mechanical clutches are dog clutches or disc clutches. When using a fixed propeller with these clutches, the transmission must be in neutral while sailing. When using a folding or feathering propeller with these transmissions you may leave the transmission in reverse while sailing.
Ok, now you’ve decided to stop putting your transmission in reverse while sailing. What to do about that noise from the shaft rotating? Is the transmission getting enough lubrication? What kind of transmission do I have? The best option to keep the shaft from rotating is to install a shaft-lock device inside the boat. Or, if you have a saildrive, your option is to switch to a feathering or folding propeller. Transmissions without oil-coolers attached are lubricated when the gears turn and splash the transmission fluid around. This will continue to happen if the propeller is turning with the engine off. If you cannot determine which type of transmission you have, contact us with your transmission’s model number and we will find out for you.
What else can you do to keep your transmission in top working order? When the engine is running, only shift the transmission when you are at idle rpm. With the engine turned off, only shift to fold or feather the prop while sailing at less than 3 knots. Change the lubricating oil in your transmission at intervals recommended by the manufacturer.
Thanks to Wikipedia for the illustration, click here for the page.