Propeller.

[kindredspirit]

Heading back towards the marina Saturday after a morning of photography. Doing about 20 knots because trying to make the lock gate opening time of half past the hour when we see a very, very slight vibration on the boat. 3 seconds later, an almighty bang, racket and vibration all over the place. Shut the engine down instantly. Look all around the sides of the boat, particularly under the stern. Look in the engine bay. See nothing. Start up the engine again. Engine OK. Put her in gear. Loud noise. Take her out of gear, turn off the engine, get a boathook and hanging over the bathing platform, go poking at the propeller in the murky water.

What's this? Can't find a propeller blade past the left hand side of the rudder. Diagnosis: Must have lost a propeller blade although we didn't hit anything.

Find out we can just about make way with the boat in gear and idling and head for the lock gates. Boat speed 3.5 knots but against the tide we were making 0 to 1 knot. SOG. An hour and a half later get in. Get the boat lifted and and lo and behold we only have 3 blades on our 4 bladed propeller. The fourth blade has completely sheared off! A clean break.

Is this very unusual? Or can it happen occasionally? I checked the propeller before the boat went into the water in the spring and it was OK.



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[Moose]

Ask Col /forums/images/icons/laugh.gif

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[kindredspirit]

Aaah! But he hit something!

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[Moose]

Did he?

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[KevB]

Got a friend who coming back from Channel Isles could only manage 18 knots instead of his normal 23. When back in the marina checked props only to find the INNER prop on one of his outdrives had totally disappeared, leaving only the rubber bush!?!?


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[Chris_B4]

I had my stainless propellors refurbed last year cos I could see some small cracks in a couple of places, probably caused over time by hitting small stuff. The chap told me that one blade was close to shearing off due to a crack that I hadn't even been able to see !

So I guess it can happen, even if you think the blades look OK

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[Sunnyseeker]

Do you have rope cutters? it has been known for some designs to cause root cavitation and blades to be lost. Difficult to prove as cavitation an be as result of several factors.
Send the prop back to the manufacturers and I'm sure we'd all be interested to see their comments here...

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[burgundyben]

I lost one off my port shaft last year, seems to happen quite a bit, you can get dye penetrant kits to check for cracks although its not widely used on boats, dont know why, seems a good idea to me.

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[Col]

No "he" didn't

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[Dave_Snelson]

Yep - lost 2 blades (well most of the blade) from a 3 blade prop on a 90 merc. They had been badly refurbished and parted company. Still went like a bat out of hell though, it just vibrated a little...

I carry a spare on board these days - and a dry suit - and a snorkel.

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[kindredspirit]

Had ropecutters on 4 years ago but took them off when a rope got entangled around the shaft anyway. (They were the disc type.)

On my previous boat with two outboards, I always carried a spare prop but I never thought of having a spare prop for this boat. I have a spare of nearly everything else, though!

I'm just thankful it happened where it did, and not out at sea in a heavy sea or off a headland. (Although I have a policy of keeping two miles off headlands if possible.)

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[oldgit]

Re: Propellers Alloy vs S/Steel.

Normally can tell when something has hit prop(loud thud etc) but unless extra large bit missing no obvious vibration.However have lifted legs on occasion to find large dent and no idea how it happened.As to stainless props,good up to a point.If you hit anything with alloy prop it will bend absorb the shock,but still be there to get you home and then bash sort of true with hammer.With stainless all that shock is going straight to your bearings/shafts/gearbox before the blade drops off leaving a totally U/S prop.

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[commissioner]

Are you on d pontoon at port hamble??

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