Need Urgent Advice on Shafts

[JC]

Had my startboard shaft break on saturday while comming back from a fishing day. Nos a great day. =(

I wasnt on the boat just my captain with some custumers. He said all he heard was some vibration that was increasing and he then went down on throttles to see what had happened. So they went in the water and to their surprisee prop and shaft were gone. Broke of right after the strut. On the port I have 1.5 inch aquamet 22 as we relaced that one about a year ago but the starboard am not sure since it was on the boat already.

Here is my dilema...

I am in El Salvador Central America with no acces to aquamet 22 other than in the US. I was ging to purchase one exactly like the one we purchased on the stb side but am not sure if they could be different lenghts between port and stbd?? I dont know maybe from the engine installations??? Should I just get one exactly the same as the oposite side or should I measure from where it broke to coupling and add some length???

Thanks for your help.. I need to move quickly...

JC

[Bruce]

JC,
Post your engine type and HP and prop size so I can see what your safety factor is.
Confirm the broken shaft was 1.5" also.

[scot]

JC,
Just curious, How far "was/is" the front hub of the prop from the aft end of the strut? Also, does the cutlass bearing extend to the aft end of the strut? Is the cutlass bearing worn badly?

[JC]

OK. Sorry not enough info.

My engines 2506btas, transmissions Twin Disc 502's , props nibral 21 x 22 4 blade, B31 Sportfish with full tower....yes the broken shaft is also 1.5 inches.

I havent "seen" the damage yet as the boat is still in the water. I understand from my conversation with one of my mates that went underwater that the shaft broke after the strut but he could not specify how close to strut... I am also wanting to see if the bearing is badly worn. Ill let you know. THey said the rudders look fine and that the hull looks to have only a scratch.

Thanks for your help.

JC

[Bruce]

JC,
If you can't get 22, 19 should be just fine for your application.

Do not use the opposite shaft length to determine your broken shaft unless you know for sure they are the same.

Make sure the key way at the prop is spooned at the end toward engine.

A loose prop, an unbalanced prop can cause this problem.

Look at the break and see what the metal looks like. A dull finish means its been cracked for a time and finaly broke. Shiney means it broke quickly and clean.

It can help try and diagnose the cause.

[AndreF]

JC,
FYI my shafts are 1 1/2 " different (done in Houston), like Bruce says, don't measure from the other one (I think your boat was repowered in Louisiana). Check distance from front of engine to bulkhead on each to see if they're the same.

[Bruce]

Andre,
That measurement would be okay if everything on a 31 was equal. But as we know it is not.
A slight deviation of bulkhead from port to stb, one strut fwd or aft of the other could be the difference of having too little or too much free shaft behind the strut.

If it is broken right at the end of the strut, which most do, measure the remaining length and tell the prop shop that length is to the back of the strut. They will determine the additional length needed.

If you are going to machine the shaft yourself, I can get that measurement for you.

[scot]

JC,

Keep us posted, we're curious as to the reasults of your investigation.

[JC]

Got the shaft out. The break was right at the front end of the prop. The shaft is 1.5 inches and the distance from the strut to prop was 1.69 inches which is a little greater than the recomended. The break looks like kind of dull like a weld looks. Ill try and take a picture. I measured from fron end of shaft all the way to the back of shaft wich measures 79.5 inches. On the port shaft (the one not broken) it measures around 1.69 inches from back side of strut to fron end of prop hub. Should I just give the shaft company those measurements???

Thanks,

JC