As you may have guessed, we've been rather busy over the last few weeks with little time to put pen to paper or fingertips to blogs as in this case. The annoying drip I'd written about in the 28 June, 2015 blog on the shaft seal which we were monitoring, continued to drip. It changed from a few drips underway to a few drips at anchor. Then the other shaft seal started to do exactly the same thing at the same time within 5 days of the first sign of drips. Now that's strange don't you think? Yes it is. When we experienced a similar problem in the Dominican Republic in 2013, it turned out to be a metallurgical issue according to the manufacturer of the seals, PSS. Surely this couldn't be happening to us again could it?

We'd had a plan, not a hard plan, but it was a plan nevertheless. We would cruise as far north as possible this season and see where we'd end up but you can't head off into remote areas if you have these sorts of issues so we felt it was best to get to the bottom of it. We spent a couple of days at anchor on Roque Island in the shifting fog on the phone to PSS going through various methods of diagnosing the problem, from sanding off the space between the bellows and the rotor to increasing the bellows pressure but nothing changed. Finally after exhausting all tried and true solutions, they suggested going to the Front Street Shipyard in Belfast, Maine, a highly reputable shipyard with fantastic facilities including two lifts of 440 tons and 150 tons and over 100 professionals capable of dealing with a multitude of servicing requirements. To tell you the truth, we haven't hauled Vanish for 2 years and 3 months, the longest we've ever kept a vessel in the water without doing maintenance. Antifouling was done in 2013in the Dominican Republic but we could have gone another 12 months. However, we've been developing a wish list of items to buy, fix and maintain so the prop shaft leak sealed the deal.

Before being hauled out, a very extensive galvanic test was performed on every electrical system on the boat. After an entire day of testing, every system checked properly except for the bow thruster which was putting a rather large amount of current into the water every time it was being used. Once we were washed down, the prop shafts were removed the same afternoon and to our amazement, we saw that both shaft seal rotors were pitted and very corroded. It was determined that the rotor corrosion was galvanic corrosion, most likely the result of the faulty bow thruster. No amount of tightening of the bellows or sanding was going to stop water leaking through this mess. They were rusty and terribly deteriorated in just over two years. Strange! We decided to have new rotors made from a highly corrosion resistant N50 stainless steel. Now we needed to figure out why the thruster was leaking so much voltage.


Initially it was thought that the grommets and seals that electrically insulate the bow thruster motor from the water might be faulty. This is actually a fairly common problem so the bow thruster was removed and new seals and nylon washers were put into place.

We'd spent a week living in the shipyard before it was decided to move us into a giant shed to do the bottom paint while we waited for the new rotors to be manufactured. After a very substantial amount of bottom preparation, new antifouling was applied and this time we used American approved Seahorse Biocop TF over a primer. All stainless steel fittings under the waterline and props were spraycoated with Petit Prop Coat Barnacle paint. We also changed the gear box oil in both bow and stern thrusters, and serviced the stabilisers as this hadn't been done for 5 years.

On one of our recent trips, we were sorely outdone in the underwater lighting display put on by practically every power boat in every anchorage in Panama. This was a bit of an indulgence but high on our priority list so it was a good time to install four very powerful OceanLED underwater lights. In perfect water conditions such as the Bahamas, the lights will shine for up to 150 ft. There are around 300 different programs which will make the lights strobe, pulse, and rotate, even to music if we desire it in every colour of the rainbow.

Although we could have stayed in a motel in town we thought we'd be more comfortable on the boat so I will gloss over the unpleasant parts of living in a shed. After a week, we were dropped back into the water and a new galvanic test showed that now the bow thruster was spiking off the chart to the right-hand side but not the left-hand side. This was apparently a key indicator of something but what? More phone calls and much head scratching before the manufacturer asked us if there was any carbon build-up on the bow thruster? We looked and yes there was black powder on the outside of the thruster. The bow thruster 25 hp motor weighing about 150 lb was removed and Mike drove 4 hours to Massachusetts to take it to Imtra Marine, who does all servicing of Sidepower thrusters in the United States. This was becoming more like a detective story than anything else we've encountered so far.

After several hours with the bow thruster motor being completely dismantled, the source of all our problems was revealed. Last year, when we were in Charleston, North Carolina, a severe thunderstorm struck a yacht in our marina. The stray electricity went through the water and destroyed equipment on several nearby yachts including us. We replaced two stern thruster batteries, the bow thruster controller and several fuses but didn't realise that our bow thruster had been compromised as it had been working normally although we only used it once or twice last year. This year, however, we had used the bow thruster a lot while retrieving the anchor and docking. The tech at Imtra said this was a very unusual occurrence as it had destroyed a lot of insulation in several field coils yet had not done enough damage to stop it from working at the full 25 hp. He said this was a very rare event as normally a good lightning strike like this makes it inoperable.



This completely explains the stray current and the high amount of corrosion seen on our shaft seals. We had no choice but to buy a completely new bow thruster motor. After installation of this motor, a galvanic test was re-performed on all of the systems on the boat and no stray current was found from any system. Stray current is an insidious problem as the symptoms from that stray current can show up almost anywhere on the boat and are seldom related to the faulty piece of equipment. Because of this, we purchased a galvanic meter and will now perform a galvanic test over all systems every couple of months on Vanish. Who knew?