Bow Thruster woes

[Paul_S123]

Was in the marina in Smir yesterday and the bow thruster looks like it took a dive...motor whirrs but only one of the props spins (very slowy) while the other just stays still...they are both turning freely by hand...any suggestions

 

[Portofino]

Check the shear pin .Its under the motor .You have to unbolt it and lift it off the gear box under the fwd cabin bed .Can be done with the boat in the water .
That’s a simple fix .
They normally have a little oil reservoir higher than the WL situated near the motor .This is to gravity feed and pressurise the gear box .The gearbox sits in the tunnel under water .
There’s seals where the prop shaft (s) exit and the oil gradually seeps out as planned preventing ingress of sea water .
If this reservoir is not timely topped up then the oil level drops and water gets sucked in to the gearbox .As time passes inevitably the gears corrode and fail .This is an expensive fix ...lift out and new gearbox if available or new whole thing motor + new gearbox if yours is obsolete.

Btw the horrible rattling noise you hear in the marina often on other boats is the gearbox cogs rotting away in seawater .
Owners oblivious to what’s coming round the corner .

A fully lubricated g box you should just hear the motor whirling ..faintly.

 

[Momac]

There may be more than one shear pin.

On my QL thruster the plastic propeller had failed rather than the metal shear pin behind the propeller.
There is a further shear pin accessed inside the boat by removing the motor.

Some bow thrusters are belt driven. I guess a belt can fail?