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Changing a starter motor at sea

Jul 1, 2016
Access to the starter was nearly blocked by engine room pipes.

Access to the starter was nearly blocked by engine room pipes.

Fiona’s engine is an 85-hp Perkins, far too big to start manually; an electric starter motor is essential. I always carry a spare starter as a functioning engine greatly enhances safety and, of course, can provide greatly improved comfort by charging the batteries, running the freezer compressor, raising the anchor, etc.

Access to the starter is not easy. Above it are two pipes carrying cooling fluids and the side is blocked by two heavy-duty batteries that power the electrical service buss. Removing them is when it is good to have a young, strong crew. Once we removed the batteries it was possible to get limited access to the starter, but first the thick copper lead that carries hundreds of amps from the separate starter battery had to be immobilized. Then it was important to tape the terminal of the lead with masking tape once it was free of the large copper nut fastening it to the starter. This lead is extremely dangerous if it — or any tool connected to it — touches ground, the resulting spark can cause burns or even start a fire. The lighter-weight solenoid leads also had to be disconnected. 

Doing all this was complicated by the fact the boat was rolling heavily and all movement required adequate support before transferring weight and passing tools or pieces to the helper. The starter was held in place by three nuts on studs set in the flywheel casing. They could be reached by a socket wrench on an extension, but only one was plainly visible. By using delicate feel, all three were removed and the starter slid forward. 

On inspection I found that the casting holding the pinion bearing had cracked. This wasn’t surprising; the rapidly spinning pinion had re-engaged with the rotating engine when power to it had failed. By good luck, the broken piece of the casting had not fallen into the flywheel casing. If it does, then to get it out the engine has to be lifted and the transmission removed to get inside the casing — an operation that can only be done in port (unfortunately, I speak from sad experience). The spare starter was installed doing all the aforementioned in reverse and worked fine. 

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