12 December 2009 Zen & the art of bow thruster maintenance

Do you have a list of jobs to do and some of them keep getting put off until tomorrow? Well, today tomorrow finally arrived and we serviced the bow thruster. It's been on the list since we left Florida over a year ago.


We'd delayed because we thought we'd do it seemed a complicated procedure better attempted when Jackster was out of the water than when she was still afloat. Most bow thrusters are in a lateral through hull tube. Not Amel, ours is a propeller on a shaft which is lowered from within the hull by means of a motor and pulley. When in the up position its fits flush to the hull.

Servicing to replace the oil and neoprene seals that keep it watertight and to change the oil, requires disengaging the shaft with propeller from the motor behind the chain locker and dropping it out of the bottom of the boat and bringing it on board to do the work. The scary bit doing this afloat was firstly, we could drop the propeller in the water, and secondly it leaves a gaping whole in the hull which seawater ingress and potentially sink. A double challenge. Don't drop and don't let water in. The answer to the first was to rig a catching 'nappy' slung under the bow. Our 'nappy' was fashioned from a large sail bag, lines tied on each corner and these fastened onto the guards rails. The hole plug a regular tennis ball.

To lower the propeller and shaft from inside the boat maker supplies a special tool – a 15” length of polished teak with cord attached the same diametre as the carbon fibre shaft. You detach the shaft from the lifting / lowering motor. Unscrew the shaft, attach the special piece of wood and lower away.

As the assistant engineer it was my job to be inside the boat and lower the bow thruster to the chief engineer who was precariously hanging out of the dinghy holding the fishing net under the lowering bow thruster. The nappy was just a back up.

We'd got the bow thruster on board without dropping it and now there was a viewing hole to the sea 4” below. With the sunlight on it the water was a beautiful pale turquoise. Not so beautiful if we got bounced and salt water slashed into the forward cabin. Solution? A tennis ball, which I just happened to have to hand, is a perfect fit to seal the hole.

Working on the unit in the cock pit we drained th e old dirty oil, replaced the old neoprene seals with new ones, chipped off some barnacles and we were ready to go back.

To replace bow thruster have one person hang precariously out of dinghy with unit in a fishing net and have the second one inside pul it back into place using the attacjed nyllon cord. There was huffing and puffing and 'you pull' and 'you push' shouted until I got a grip and hung on desperately while David climbed back on board and could use his greater physical strength to pull it back in place. It all went back together without any bits left over and we hadn't sunk. The service should last for 2 years and we became intimately acquainted with another essential part of the giant jigsaw puzzle that is our boat.

We finished the day with a well deserved gin and tonic and a kiss for the chief and assistant engineers.