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http://www.marinedieseldirect.com/universal/200157/universal-owners-hurth-transmission.htmlUNIVERSAL DIESEL WITH HURTH TRANSMISSION Model HBW-50 (2:1)Used on Models 12, M2-12, M-18, M3-20, M4-30, M25 and M-25XPModel HBW-100 (1.8:1)Used on Models 30, 35, and 40Model HBW-150 (1.9:1)Used on Model 50Model HBW-150 V-Drive (2.13:1)Used on All of our V-Drive ModelsCAUTIONDO NOT LEAVE GEAR IN FORWARD WHEN SAILING. GEAR MUST BE IN NEUTRAL FOR FREE WHEELING OR SHIFTED INTO REVERSE TO LOCK PROPELLER WHILE SAILING.To lock the propeller vertically in line with the keel, mark the coupling and POSITION GEAR IN REVERSE. This will prevent slippage and damage to the clutch.CAUTION: TRANSMISSION MUST BE LEFT IN NEUTRAL WHEN SAILING, DO NOT LEAVE IN FORWARD GEAR WHEN SAILING WITHOUT POWER AS IT WILL DAMAGE GEAR.