How to troubleshoot lackluster bow thruster on the hard?

[pukeanddie]

I have an old 5hp key power bow thruster in my Camano. Last season it was fine, except when I was coming into the dock at haulout at the end of the season. I heard it running but it had no effect. I tested it on the dock by holding the bow and running the thruster and felt no pull.

With the boat out of the water, I did notice a fair bit of growth in the tunnel. How much would that effect it's performance? In the yard over the winter I have been able to confirm that the prop is not spinning on it's hub and it appears to run fine when testing in short bursts out of the water. The wiring terminals all look fine.

Can I just chalk this up as a marine growth issue, or is there a way to further test and confirm it's ok while still on the hard?

I'd hate to launch the boat and find I still have a problem.

 

[Flatswing]

Step 1: check the voltage drop with thruster running, it may surprise you

 

[fgarriso]

The yard you're working with should be able to test for voltage and current. You may need to clean all battery connections. Also load the battery you're using.

 

[Comodave]

You probably don’t want to run the thruster with the boat out of the water. It may damage the thruster. I agree on checking all the electrical connections. That is the most likely area that would have a problem. Also the battery can be bad. Or the thruster could be going out, but check the simple easy stuff first. Are the battery cables large enough?

 

[Bacchus]

Not familiar with key power but SidePower recommends AGAINST anything other than a brief burst when out of water.
Yours likely has a shear pin somewhere in the drive that connects the prop to the drive.
Look for applicable manual or call the mfg or dealer

 

[mvweebles]

Not familiar with key power but SidePower recommends AGAINST anything other than a brief burst when out of water.
Yours likely has a shear pin somewhere in the drive that connects the prop to the drive.
Look for applicable manual or call the mfg or dealer

Sheer pin was my first thought too since it sounded like it was working fine until very recently. However, OP says it's not spinning on the hub so maybe not. I'd pull the prop and see - should not take long.

Side story - After my thruster was installed, when I went to first use it, the thruster ran but had no thrust. One of the many incompetent gifts from the boneheads who originally worked on Weebles was neglecting to install the sheer pin.

I don't know what it takes to break the sheer pin, but in theory, if there's a lot of growth in the tunnel - especially hard growth like mussels - either the prop will break or the pin will break.

Good luck. Please update when you know more......

Peter

 

[Bacchus]

If the confirmation of prop not spinning on hub is that it rotates with short bursts while out of the water... there could be just enough drag /ingagement to spin the prop with no load.
My thinking is prop could spin w/o load but with load not spin or only slowly and not provide thrust.
Have you tried rotating the prop by hand or with a stick w/o engaging the thruster?
Bottom line... Best bet would be to remove the prop(s), clean the props, hub & tunnel, bottom paint the tunnel lube & reassemble.

 

[Endeavor GB 32]

Our boat is in the Semiahmoo Marina in Blaine, WA. The growth of mussels here is amazing. Our bow thruster becomes useless after 4-5 months due to mussell growth in the tunnel. We have to have a diver clean the tunnel regularly. The thruster will still run and turn, but the flow disruption caused by the mussels render it completely ineffective. So your theory might be spot on. Good luck!
Regards,
Scott

 

[chriscritchett]

No real experience, but I have to believe growth in the tunnel is a huge hit to performance. Water cant get TO the prop easily, and then it can’t go anywhere afterward. And if the prop had growth, too - which you would assume if the tunnel wasn’t cleaned out - game over. Bet it still made that fun noise, though.