Signs of a Locked Up Transmission

Boating can be an adventure as well as educational. You shift into neutral to bypass the starter’s neutral lock, put your key in your boat’s key switch and give it a twist. Maybe it starts, maybe it doesn’t. Even if it starts, it stalls when you try to shift into gear. After ignominiously hauling the boat out of the water – without it ever leaving the trailer – you think about how, like so many things “boat,” testing can be as expensive as the repair. In this case, though, the testing is quick, dirty, effective and cheap.

  1. Shift System

    • If you have remote controls rather than a shifter mounted on the engine, the shifter moves the cable connects to the shift rod under the front of the engine. The shift rod connects to the transmission in the lower unit. Move the shifter and watch the shift rod under the front edge of the engine. It should move. If not, check to ensure the shift cable is connected.

    Direct Testing

    • If you shift the transmission to neutral and start the engine, it stalls. Try it from the other end. Shift into “Neutral”; don’t start the engine, but kneel at the rear of the outboard where you can touch the propeller instead. Propeller blades, even plastic propeller blades, have sharp edges, so put on some heavy, leather gloves. Try to turn the propeller clockwise, then try to turn it counterclockwise. If it won’t move, the gears may have locked up or the shift linkage may be bad.

    Kneel to Your Outboard

    • Remove the small grills or grates on the sides of the outboard’s exhaust tunnel, the “leg” that connects the lower unit where the propeller shaft lives, to the powerhead -- the internal combustion engine that powers the whole show. Look into the opening and you’ll see the joint between the shift rod and the shift shaft. If the shift rod and the shift shaft are disconnected, insert a screwdriver and reattach the shift shaft and shift rod.

    Seizure!

    • If the shift shaft isn’t disconnected and the propeller refuses to turn when the transmission is in neutral, your gearbox is locked up pretty effectively. Remove the nuts or nut-and-bolt combination that holds the lower unit to the outboard. Pull the lower unit straight down and out of the exhaust tunnel. Inspect the shift shaft for bends. If the shaft appears straight, ensure it’s in the neutral position. Look for fishing line around the propeller shaft, near the lower unit seal – a big enough wad of it will stop an engine when you try to put it in gear. Finally, try to turn the propeller once more. If it won’t turn, the problem definitely is a locked up transmission, and repairs require professional help.