Corrosion Damage Bow Thruster

[South lake]

As the folks who take care of my 2010 R25 were prepping it for the new season they found that the shaft of the bow thruster was severely corroded.



When they started working to clean it up they determined it's destroyed and now I'm looking at a replacement.

The boat is always docked at my house in fresh water. No other boats around as it's a private dock. It is plugged into shore power when docked. Never had a corrosion issue before.

When I know Ranger Tugs is open I'm going to call and see if there is a wiring schematic for my boat that I can get. The service manager also asked me to ask RT if the thruster is supposed to be bonded.

Just curious. Has anyone else had a similar experience?

 

[JeffE]

I've had a Sidepower thruster experience crevice corrosion on it's drive shaft. The source is from sitting in water and non-usage. Stainless steel corrodes when it doesn't have oxygen and is wet.

The prevention is to run the thruster for a short time frequently, even when you're not taking the boat out.

Jeff

 

[Scuffy]

Have the anodes been replaced on a regular basis? How did they look when this inspection was done. Fresh water might require a different anode material as the saltwater anodes I believe are aluminum. We installed a galvanic isolator to extend the life of the anodes. Some marinas have more issues with corrosion caused by electrolysis than others due to some boats introducing more electric current than normal into the water. I have heard of a salt water boat needing a bow thruster shaft replaced because the anode was not replaced when needed. If I remember the shaft is not hard to install but was expensive.

 

[Kaisardog]

fresh water anodes should be magnesium not aluminum. that being said, that is an unusual amount of corrosion for one year. i assume the bow thruster shaft looked OK during last year's hauls ?

if you spent time at another marina and there was an improperly wired neighboring boat near you , that could have caused the extensive amount of corrosion i see. old carvers are particularly notorious for being a source since some owners have improperly wired them themselves..

do let us know what you find out. we've kept our boats in lake erie for years, with both AL and MG anodes, and never seen the kind of corrosion i saw in your picture.

 

[Kaisardog]

more on the bow thruster wiring; : Imtra.com has the install manual on line for this thruster. p. 15 that manual shows wiring to be + terminal of battery to on/off switch to slow-blow fuse to terminal of motor. other terminal of thruster motor goes to ground.

 

[South lake]

Quick update as I'm still waiting on a call back from the boat yard.

As to the posts from others (Thank you!).

1) Thrusters get lots of use. I use the boat 4 or more times a week during the season and use the thrusters every time I dock so plenty of usage.

2) I haul the boat every fall and take it to the same boat dealer/service facility. Know them all well and have dealt with them for years. They go over the whole boat including thrusters and they caught this as part of my normal winter maintenance. Anodes replaced as needed each year.

3) No signs of corrosion last year or any prior year.

4) The boat is docked at my private dock, no marina, on a lake in West Central Ohio. Other boats in the vicinity are pontoons and 1 sailboat, none of which use shore power and all are some distance away. My boat is plugged into shore power when docked.

Here's a silly question as I've been trying to think of anything that's changed in the environment the past year. Last year our Homeowners Association installed aerators in our channel. The closest one to me is down the channel about 100 feet away. Could there be some electrical issue from the aerator compressor that could cause something like this? Don't laugh, I admit my knowledge on this is below a 1st grade level.

On a positive note, I reached out to Ranger Tugs and in a short time was connected to Andrew. I still can't get over the fact that I buy a boat 6 years ago and get that kind of customer service from the manufacturer. Just a great company with really great people.

Will post more as I get more info.

 

[tlkenyon]

I, too, live on an inland lake.

What it your dock made of and is there any corrosion on it?

Your thoughts on the aerators are spot on. We have had them on our lake (thankfully not near my dock) and the lake residents were told to stay well away from them because of the possibility of electric shock.

TK

 

[South lake]

Boat docks in a slip, stern in, with a seawall along the starboard side and at the stern. Shore power stanchion is on the seawall walkway at the stern of the boat. A wooden dock runs along the port side. Been docked that way for several seasons.

Aerator compressors are in cabinets sitting on seawall walkways, again, a pretty good distance from my boat. Hoses run from them along the channel bottom.

 

[stwendl]

Take a multimeter in voltage mode, attach one lead to the ground on the shore connector and one to the ground of the boat connector. Do not plug the boat into shore and see if you get a reading. If you do, add a galvanic isolator.

Might also hang a sacrificial anode on a wire over oars and connect it to ground be on the boat. Easier to check and change.

 

[Red Raven]

The galvanic isolator Is a good idea if the problem is external to your boat....Have you checked all wiring in your boat for a lose wire in the bilge? Is there water trapped in the bilge near the bow thruster contacts? Electrolysis from a loose 12V wire could also explain the sudden corrosion.