Folding prop -repair or replace?

[lumphammer]

The gear teeth on my two bladed folding prop are worn so that it is possible to open one blade without the other moving. I would be interested in the forums opinion on whether it is possible to repair this or should I replace the prop?



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[scottie]

any idea what make of prop

IF! you can get them i think that blade will most likley cost 60-70% of new prop but still leaves the any wear in the boss pins

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[PeteMcK]

You can certainly get replacements for Radice props but, as Scottie says, they cost a big chunk of the complete renewal and if the holes locating the pivot pins in the boss are worn, you could be throwing your money away.

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[lumphammer]

Unfortunately, the prop came with the boat and I don't know any of the details about prop manufacturer or size

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[davey]

Clean it up with steel wool and look for information stamped on it such as makers name, diameter and pitch. There may also be a part number. Wear (corrosion?) of the gear teeth suggests that the propeller might only be brass and not bronze. All is not lost as there are firms on eBay who will rebuild worn propellers by bronze welding. Whatever you do unless you are a millionaire DO NOT GO TO A CHANDLER WHO CALLS YOU "SIR" AND RIPS YOU OFF!

In actual fact some propeller manufacturers will want to sell you a new propeller. Whilst this may be better and more efficient it may empty both your wallet and your bank account. The bottom line is that its most likely that the fuel savings will NEVER recoup the cost of the propeller

Good luck!

PS Why not fit a second-hand fixed propeller as a temporary measure? You will need to know the propeller "handing" (left or right) and the shaft diameter and taper. Three common tapers are the Metric (AKA "Vetus" or "Continental") which is 1 in 10. Next comes the British taper which is 1 in 12. The last one is the North American SAE taper of 1 in 16.

Most Yanmar engines use right handed propellers but the older YSE, YSB and YSM use left handed props as does the Petter Mini 6. With a fixed propeller on a sailing boat you might want it to be a little undersized in order to lessen the drag. Another way is to choose a prop with fairly narrow blades. Motorboat propellers with a high Disc Area Ratio (wide blades) will give more drag.

 

[Tranona]

As this thread is over 11 years old, would guess that lumphammer has solved his problem now.

 

[davey]

Ah yes but there are bound to be other people with similar problems so all is not lost. Sadly these days it is rare for people to be given a proper education because of the dreaded Health And Safety At Work Act. Back in my school days we had an excellent metalworking shop and boys would leave school well versed in lathe-work and silver-soldering. Unfortunately the Natural Gas that is now used everywhere does not give such a high temperature as the old Coal Gas (AKA Town Gas) Back then one of the tasks that we were given was making a brass beaker. The construction of this was an exercise in Graded Soldering. Sub-assemblies were hard-soldered using red heat. Next they were assembled using "Easyflow" (Note that the modern "Easyflow" is not the same as the old British Easyflow as the unregistered name was taken over by a different company) The final piece, the beaker base, was installed using soft solder. That was over fifty years ago and I still have the beaker!

Provided that the propeller metal has not become crumbly it should be possible to repair it. If however it is de-zincified brass it will only be fit for using as a pattern. Some countries now use the throw-away mentality. For example chain-saws that have no proper bearings. With these the crankshaft runs directly in the aluminum crankcases and once the "bearings" wear the saw is only fit for scrap unless it can be reverse-engineered by installing suitable bearing-bushes. IMHO a good bronze propeller should last for several decades so the one with worn gears seems extremely suspect.

A perennial problem however is caused by machinery that is only rated for pleasure-use. When such machinery is used 24/7 owing to blue-water-cruising it may give trouble. For example there are small diesel engines that are known to be capable of running Thermo-King truck fridges for at least 30,000 hours. Similar engines mated to a marine gearbox suddenly become "Pleasure Use Only 500 hours per year maximum" but at that rate will the engine last for sixty years? The answer to this conundrum is of course that the gearbox is too small and for serious use it needs to be upgraded.

 

[johnalison]

There is a difference between such an engineer's approach to these problems and the rest of us without such knowledge. Although my 18-yr-old Volvo folding prop shows no sign of giving up, if I saw that the gears were wearing I would probably be content to fork out a large sum for a new part or replacement in the hope of trouble-free sailing.