Selecting Gear Appropriately on an Outboard Motor

Are You Damaging Your Gearbox when Altering Gear?

Clutch Canine Gearboxes

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

If you choose gear slowly and caretotally with these gearboxes you’ll truly 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 change or someday your decrease unit will not have any drive and it will consistently leap out of gear.

Firstly I’ll explain how the decrease unit/gearbox works.

They have an input shaft that’s driven from the engine or ‘energy head’. (This enter shaft is called the driveshaft. The driveshaft has a gear linked to the bottom 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 may be 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 inside spline that’s in fixed mesh with the propeller shaft.

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

When the Clutch Canine is moved to pick out gear it engages with the identical sized sq. teeth on the actual gear that’s being engaged.

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

If you choose gear slowly, the Clutch Dog will slowly move into mesh with the gear. This gradual movement causes the enamel of the gear to ‘skip’ over the teeth on the Clutch Dog. This continuous skipping wears away the good sharp edges of the teeth and will eventually cause the motor to leap out of gear.

Find out how to Select Gear

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

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

· Don’t shift into reverse if you end up moving forwards quickly. It creates a huge amount of pointless pressure on the gearbox (and engine). Sluggish the boat down of the airplane, come back to an idle and pause in impartial to let the boat gradual right down. Reverse is solely a reverse, not a break…

Engine Idle Speed Too High

· Another cause for damage being carried out to the Clutch Canine is your idle velocity could be too high. For those who motor is idling higher than round 900rpm in neutral you can be doing damage each time you might be deciding on gear.


· Be certain that your idle velocity is set to what the Producer recommends!

· Positively choose gear

· Pause in neutral between gear changes.

· Let the boat gradual down before turning into reverse

· Have the gear oil changed each 100 hours or annually, which ever comes first.

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