DIY Boating
When the prop-nut goes AWOL
TA big bronze prop for a launch or large sailboat can cost several thousand dollars.
Even if you aren’t able to use chart tracking to identify the exact location, a high-resolution side-scanning sonar, like the newest Active Imaging units from Lowrance, can resolve even small objects like a propeller with remarkable clarity provided the water isn’t too deep.
Of course, this won’t help if you have a single-engine boat, so put a call out on the VHF and see if anyone nearby can help.
Having located the missing prop, we fortunately had a number of experienced divers on board who went into full recovery mode, and with the prop back on board we considered our options. Given the prop weighs about 20kg, re-fitting it in situ wasn’t realistic, even if a replacement nut and locking washer were available.
For most outboards and sternleg installations though, the leg/motor can be turned to full lock before being tilted up, enabling access to the prop shaft. The shear pin can be replaced, if that is the issue, or the prop and retaining nut replaced if you have a spare nut on board.
Tip: If you ever replace your prop, keeping the old one on board is not a bad idea, with a spare nut and shear pin, as an emergency back-up.
In our case we motored slowly home on one engine, after calling Coastguard and reporting our situation. If you have a single engine and no way of replacing the missing unit or repairing a sheared pin, a Coastguard tow is probably your best option.
If you ever replace your prop, keeping the old one on board is not a bad idea...