propeller not turning

verestsailnet · #1 08-19-2012

I have an Islander 32 with a volvo penta MD7A inboard. The engine turns on. Transmision spins the shaft turns forward and in reverse as expected; however, the prop does not turn. My thinking is that the propeller became loose. I see the propeller is there but it simply does not turn and the shat is turning. Help needed before diving in to determine how to fix it. Recently I had the shaft fitted with a new zink. Is it posible that they removed the propeller and did not install it correctly? It worked fine for about two hours. How is this posible?

Thanks

ParadiseParrot · #2 08-19-2012

Missing key maybe?

verestsailnet · #3 08-19-2012

Thanks, a minute ago I spoke with to a diver that provides propeller replacement and he stated that it is likely that the key broke.

SimonV · #4 08-20-2012

Either the keys sheared, or the prop fell off.

DivingOtter · #5 08-20-2012

Sounds like a bad keyway

DivingOtter · #6 08-20-2012

They wouldnt have removed the wheel ( well they SHOULDNT have ). The zincs around the shaft should piece around it. Just make sure you use a reputable INSURED diver. There are way too many fly by nights out there.

verestsailnet · #7 08-20-2012

Great advice. It is good to know that the propeller was not removed when replacing the zinks. I'll will check on insurance and reputation, before hiring the diver.

The key must be broken. I must have been bad for a while and it finally broke. If anyone knows what could have couse the propeller key to shear that would be great knowledge to everyone.

thanks

SchockT · #8 08-20-2012

I doubt very much the key broke, because if it did, where would it go? It is trapped half in the prop keyway and half in the shaft keyway, and there is zero clearance between the shaft and the prop hub. It is possible that the key fell out, but if it is anything like my shaft that is next to impossible to. The most likely scenario is that somebody installed the prop without the key, and instead was relying on nut tension and the shaft taper to keep the prop tight. Regardless, if the prop has been spinning on the shaft, you are likely going to have to deal with a damaged prop and shaft. I would be surprised if a diver could do anything more than tighten it up enough to get you to the nearest haul out. If you have a haul out nearby you should get a tow to the lift, and put the diver fees towards the haul out where you can properly inspect and repair the problem.

DivingOtter · #9 08-20-2012

Many things could cause it to give. Poor fit, corrosion due to old age, fatigue or even play in the cutlass bearing causing "chatter" in the shaft resulting in harmonic imbalance or sympathetic resonance over time causing the break.

DivingOtter · #10 08-20-2012

Quote:

Originally Posted by SchockT

I doubt very much the key broke, because if it did, where would it go? It is trapped half in the prop keyway and half in the shaft keyway, and there is zero clearance between the shaft and the prop hub. It is possible that the key fell out, but if it is anything like my shaft that is next to impossible to. The most likely scenario is that somebody installed the prop without the key, and instead was relying on nut tension and the shaft taper to keep the prop tight. Regardless, if the prop has been spinning on the shaft, you are likely going to have to deal with a damaged prop and shaft. I would be surprised if a diver could do anything more than tighten it up enough to get you to the nearest haul out.

Relying on nut tension alone wont work. As soon as torque is put onto that shaft it would free spin. Ive seen keyways that were too big resulting in not being able to remove the wheel, and keyways that were too small resulting in a shockload everytime gear was engaged.