How do I replace the cutless bearing on an Arcona 340?
I can feel some movement at the propeller on my Arcona 340 and suspect the cutless bearing needs replacing. How do I identify the right replacement, and can it be changed without removing the shaft?
Answer
First check whether your Arcona 340 has a saildrive or a conventional propeller shaft, as a saildrive has no external rubber cutless bearing and movement at its propeller needs a different diagnosis. For shaft drive, replace the bearing ashore after confirming its dimensions and retaining arrangement, using a suitable extractor and supporting the shaft.
Check the drive and movement
Look behind the engine and beneath the stern. A saildrive has a gearbox leg passing through the hull, with the propeller mounted directly on its lower section. A conventional installation has a shaft running aft through a stern seal to a bearing in a stern tube or separate supporting bracket.
Do not order a bearing by boat model alone. Engine installations, build years and later conversions can differ. The information available here does not include a verified bearing size for the Arcona 340.
With the boat ashore, grip the propeller hub and lift it gently while watching the shaft where it enters the bearing. Movement between the shaft and rubber suggests bearing wear. Movement within a folding propeller can come from its pins, bushes or hub. On a saildrive, investigate the propeller assembly and output shaft instead.
Isolate the engine starting circuit before handling the propeller, and have the yard support the boat securely.
Identify the bearing dimensions
You need three measurements for a replacement: shaft diameter, bearing outside diameter and bearing length. Measure the exposed shaft with a vernier calliper. Establish the bearing sleeve dimensions from an accessible end, the removed bearing or an installation drawing.
A 25 mm shaft does not establish the bearing's outside diameter. Bearings with similar bores can have different metric or imperial outer sleeves. Bronze and composite sleeves are available, and their installation requirements can differ.
- Photograph the bearing housing, exposed bearing end and any markings.
- Ask Arcona or the original installer for the shaft-line specification, providing the hull number and build year.
- Check whether the housing has retaining grub screws, a shoulder or a removable carrier.
- Buy the bearing only after confirming all three dimensions and the sleeve type.
Vetus and other marine bearing suppliers offer several sizes. A bearing reported to fit another yacht is not enough to confirm a match for yours.
Remove propeller and extract bearing
Record the propeller assembly order before dismantling it. Folding and feathering propellers have model-specific procedures for blade pins, locking screws, tab washers and shaft nuts. Follow the propeller maker's instructions.