Can a thruster tunnel get clogged?

[Streff]

We have been anchored for a week in an area with lots of sea cucumbers floating by. Tried to engage my bow thruster yesterday and initially nothing happened. Stern thruster worked fine. Later in the day, I tried again and the thruster engaged but it sounds labored/different and moved much less water than usual.

There are no error codes. The unit is an electric Westmar unit. I started thinking of the possibility that the thruster tunnel got clogged or choked with sea vegetation and debris which there are plenty around. Is that even a possibility?

My next step is calling a diver to take a look..

Any comments or ideas would be much appreciated.

Thank you

Streff.

 

[Comodave]

Yes, it can happen. Be careful running the thruster because it could break a prop or a shear pin if the unit has one.

 

[rgano]

It is a largish opening and "stuff" can lodge in there, but I doubt it happens very often. You don't have a method to either get in the water to check or a waterproof camera? With Comodave's advice in mind, maybe you can touch it back and forth to see what happens with the hope it loosens up.

 

[OldDan1943]

Some folks put a grate on each side of the tunnel opening.

 

[psneeld]

There are DIY earmuff style covers when docked made out of PVC and small buckets/ice cream containers, etc...... push on, yank out with a line/boathook. They look like the oversized version of the old style outboard earmuff style flushers.

Can't help you with anything more obvious that you probably already tried.

 

[wkearney99]

Yep, they can get clogged, and potentially have blades get broken. Though most usually have a shear pin that's supposed to fail first. I had a Sidepower bow thruster shear pin fail after 'something' got sucked into it. On inspection one of the blades was cracked. I had both replaced, and iirc it was done out of the water.

 

[Streff]

Thank you all for the comments. I will definitely get something over the openings at the next haul-out. I got in the dinghy and used an endoscope to examine the STD opening .. i saw vegetation inside the tunnel and some spongy entity floating at the opening but attached to something around the blades. Could not get a stable image.

Diver is trying to make time this Saturday. I wish I had a wetsuit or at least a scuba mask onboard to have a go at cleaning. I keep putting off buying a Hooka setup.. Not anymore.

Thanks again folks,

Streff

 

[boomerang]

Plastic bags from bagged ice, plastic grocery bags and mylar balloons are notorious for floating just on/under the surface, a perfect target to get sucked into your thruster tunnel. Years ago, on a customers sailboat, I pulled a removable thru-hull speed transducer to clean the paddlewheel blades. When I pulled it, a damn ice bag came in the 2" opening with the inrush of water. It got hung up in the thru-hull check valve & the boat had to be hauled so we could clear the bag out of it. That was an expensive day all because of a little plastic bag.

 

[Streff]

Today, The diver cleaned & freed the tunnel and checked blades & movement. The thruster moves but it does sound different for sure. Started digging into things .. The manual seems to indicate that there ought to be an oil reservoir to feed SW90 gear oil. My bow thruster does not have a reservoir. I see the 1/4” NPT plug where a reservoir would be attached.

Interesting the thruster are 14 years old.. so probably need oil. I bought various parts to make a reservoir and gravity feed oil.

Not sure if that’s the issue but will see.

Streff

 

[rgano]

My SP55 thruster bogged down due to excessive carbon dust from the brushes. Cleaning all that out brought it back. The SP tech said I have enough brush material to last a long time yet. Yours could have same issue or maybe worn down brushes.

 

[HypnoBob]

Yes, we caught a fish with ours. Jammed it right up. Removed the fish and we're thrusting again.

 

[backinblue]

The tunnel is generally not far underwater. A mask and snorkel should be good enough to take a look. On my boat, I have SidePower bow and stern thrusters. The stern has a sheer pin that can be changed from inside the boat, it's at the motor, not the prop. The bow blades are designed to break. There is a pin at the prop, but it's not really a sheer pin. It's a "drive pin". The prop is plastic and will fail first. Ask me how I know all this! I'd be wary of trying to dislodge anything by cycling the thruster. Better to clear it by hand. Also, switching direction on a thruster without a pause in between can sheer a pin.

 

[Hippocampus]

We’re in cold water much of the time. Have taken to running the thrusters every few days even if not moving the boat. Antifouling works better with motion across the blades periodically. Always run the thrusters before taking off. But that’s just to confirm they work.