Selecting Gear Correctly on an Outboard Motor

Are You Damaging Your Gearbox when Changing Gear?

Clutch Dog Gearboxes

Outboard motors and most stern drive gearboxes (like Mercruiser’s Alpha drives) use a Canine Clutch set up for selecting and shifting gear.

If you choose gear slowly and careabsolutely with these gearboxes you will actually be damaging the gear box.

Do you hear a grinding or chattering noise when deciding on either forward or reverse gear?

When you do, something needs to vary or in the future your decrease unit will not have any drive and it will continually soar out of gear.

Firstly I will clarify how the decrease unit/gearbox works.

They’ve an input shaft that’s driven from the engine or ‘energy head’. (This input shaft is called the driveshaft. The driveshaft has a gear linked to the underside of it called the Pinion gear. The pinion gear is always in constant mesh with the forward and reverse gears. When ever the motor is running, the pinion gear is rotating the forward and reverse gears. Between the forward and reverse gear there is the mechanism that selects gear. This is called the Clutch Dog.

The Clutch Canine sits on the propeller shaft that protrudes out the back of the gearbox and drives the propeller. The Clutch Canine has an internal spline that’s in fixed mesh with the propeller shaft.

Image the Clutch Dog having a front and a back. At every end it has giant, square teeth. When you select gear on the motor you move the Clutch Canine forwards and backwards alongside the propeller shaft.

When the Clutch Canine is moved to pick gear it engages with the identical sized sq. tooth on the particular gear that is being engaged.

Do not forget that each of the output gears (forward and reverse) are rotating as they are in constant mesh with the pinion gear (input gear).

If you choose gear slowly, the Clutch Dog will slowly move into mesh with the gear. This slow movement causes the teeth of the gear to ‘skip’ over the teeth on the Clutch Dog. This steady skipping wears away the great sharp edges of the tooth and will ultimately cause the motor to leap out of gear.

Tips on how to Select Gear

· The way to keep away from doing damage to your gearbox is to positively select gear. This means to literally bang the engine into gear so you hear one clean engagement of the gearbox, not chatter.

· You must also pause in neutral when shifting from forwards to reverse or vice versa. This allows the propeller time to stop spinning.

· Do not shift into reverse when you are moving forwards quickly. It creates an enormous quantity of pointless force on the gearbox (and engine). Sluggish the boat down of the aircraft, come back to an idle and pause in impartial to let the boat sluggish proper down. Reverse is purely a reverse, not a break…

Engine Idle Speed Too High

· One other cause for damage being finished to the Clutch Canine is your idle speed could be too high. For those who motor is idling higher than round 900rpm in impartial you will be doing damage each time you are choosing gear.


· Make positive your idle speed is set to what the Manufacturer recommends!

· Positively select gear

· Pause in neutral between gear changes.

· Let the boat slow down before turning into reverse

· Have the gear oil changed each a hundred hours or annually, which ever comes first.

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