stub shaft bent

[doc g]

Hoping someone can help me out with some spec's ........How much can a 2.5 " stub shaft be out? What is the spec on how bent it can be and still be OK?. Also what is the spec on how bent it can be and still be repaired safely? Thanks in advance ! ...............Pat

 

[Fanfare]

I don't know any of these answers, but a good prop shop will. They put the shaft on a special roller table to check them. Often they can be trued up. If they cannot straighten it then you should replace it.

How is your muff coupling? It could be damaged as well. Also, if the stub got bent then you should probably check the main shaft. Did you hit something?

Some on this forum have replaced two-part shafts with single long shafts. Might save some money and cut drag.

 

[Boatsb]

Its probably better to replace everything and use a one piece. Shafts can be straightened but how straight will be determined by how good the shop is. Ive seen things straightened to within .002. Ive seen other shops work where it was closer to .05


if the coupler is out it will transfer down stream making the whole system out of spec.

 

[doc g]

I actually found out that 2- 3 thousands out is ok and that up 175 or so thousands can be straightened, It can not be fixed if the bend is in the taper. We also found that my muff coupling and aft - most strut were loose , so maybe the shaft is not bent . It's in the shop now ....fingers crossed .......Pat

 

[saltshaker]

I'd be concerned about the condition of the muff coupling and shafts if they've been loose for a while

 

[dsharp]

If you hit something hard enough to bend a 2 1/2" shaft you would know it. They usually bend right in front of the taper. Do you think it's bent or are you just chasing a vibration?

 

[rsmith]

I'd be concerned about the condition of the muff coupling and shafts if they've been loose for a while

I'd be very very worried about the muffs being cracked or ready to. It happened to me. That's how I ended up with one piece shafts. Biggest improvement I've ever made.

 

[doc g]

shaft and coupling are at the prop shop being checked out .Why is one piece so much better? ......Pat

 

[saltshaker]

shaft and coupling are at the prop shop being checked out .Why is one piece so much better? ......Pat

You eliminate the potential for failure and alignment issues that can come from the coupling. Less drag in the water also helps a bit with performance. I had mine an alignment issue from a bent strut so we dropped everything and sent it all to a prop shop to be checked and trued. Mine were OK except for one stub was slightly out and had wear from the miss alignment. Cost to manufacture the 4' stub with the machined end for the coupling was about the same as a new 12ft shaft. I had a good spare stub but decided to put new one piece shafts in while everything was out. Boat was smoother and picked up about 1-1.5kts. Well worth the investment.