Bolt head broken off prop shaft collar

[ebbtide]

Okay so there's no owners manual for our boat...That figures! Can you imagine if toyota and ford did that.Oh thats right they're still in business!Well we'll just have to keep writing our own manual and keep asking questions and scanning this forum. The good news is that there are so many experienced owners with incredible knowledge that who needs a manual anyway.

[dowdster]

My diver went down to scrub the hull and discovered that the top bolt in the prop shaft collar (pictured in the string above) had sheared off and the bottom bolt was loose too, so the whole collar was very loose. He asked if I had been getting any terrible vibrations and I hadn't even noticed it. Now I've got the boat hauled. I'm also checking to be sure that the shaft hadn't been bent/damaged. This seems to be a common weakness?

[Capt Ron]

Thanks for the owner's manual question. I got a laugh out of that one!

Seriously, if you do decide to drill out the broken bolt use a left handed drill bit with the drill in reverse. The heat and vibrations from the drilling process may just walk the broken bolt out. If not then proceed with normal bolt extraction methods.

Another tip. Soak the threads with a penetrating oil product called "Aerokroil". It is without a doubt the best penetrating product made.

[gfuller]

I know this is an old thread but does anyone have the bolt sizes for the cutlass housing? I'm in the same boat so to speak and need to extract one and replace the other (bent) one.

any advice is HUGELY appreciated. Thanks guys... I'll take some lovely pics of the process...

[RobS]

Isn't the bent one a good exemplar?

[gfuller]

Hi Rob,;

Not really and here's why. The bold on the left is the one that was loose (bottom of housing) and I believe had broken off (especially now compared to the top bolt) The bolt on the right is from the top of the housing and appears to be stretched or something? I ordered a scope so I can look in the holes and hopefully get a better idea of what is going on in there. Now that i examine the shorter bolt that I thought was broke, I'm not really sure if it is... I guess I could try threading it back in there or just wait until the bore scope arrives...

[RobS]

I think it is an illusion and it is eroded, not stretched. Look at my "etch-a-sketch" - the top and bottom "calipers" I drew are the exact same size and both of them span the same number of threads

[gfuller]

You're good!

So the length of said "tapered" bolt should be correct and the shorter of the two appears to be broken off?

[RobS]

Anything is possible from the factory and the 17 years that passed since you acquired her - one of the bolts could have been shorter from day one, one could have been replaced with a shorter one over the years, etc. Also, don't go by the "cut-off" appearance since it is not uncommon to cut to length in the field. Just make 100% sure that whatever you replace it with grabs all available threads WITHOUT bottoming out..

[gfuller]

Good call.

Thank you very much for your quick and educated response on this. I'm going to get in there with a scope and see what I'm working with and then do a little bolt shopping. Are these brass/bronze? what would I replace them with material wise?

[RobS]

Silicon bronze