I have a twist in the splines on my propshaft. It's pretty severe but does not cause any vibration or problems.

My first question, do I need to replace the propshaft?

If I do need to replace it, how much should I spend and where should I get one?

Last but not least, if replacement is necessary, how difficult is it to replace? Would you recommend a professional?

I think the shaft was damaged when I hit bottom (rock) and narfed up my 4 blade hydromotive pretty bad. Is it possible that the shaft is twisted from just normal wear or is it more likely twisted because of the contact with the bottom/rock?

Sounds like you are lucky you didn't break the prop shaft AND lose the prop.
I don't know what engine/drive or boat you have but if your engine/drive package doesn't absolutely require a solid hub run with a rubber or plastic hub. They prevent this type of damage.

ThrottleUp-Thanks for the reply...but now that I have the damage, I'm still looking to repair it.

I'm running a 25' Eliminator Eagle with 500HP.

Help?!!

IT'S TWISTED FROM WHAT YOU HIT OR LAUNCHING OUT OF WATER AND NOT THROTTLING BACK. IF YOUR PROP WAS ALL MESSED UP WHEN YOU HIT BOTTOM THEN YOUR SHAFT MAY ALSO BE BENT. VIBRATION WILL COME FROM THE PROP BEING BENT OR EARS ROLLED OVER. I HAVE RUN TWISTED SPLINES WITH NO PROBLEMS. WHAT IS EXCESSIVE TWIST??? IT'S FOR YOU TO DECIDE. REMEMBER WHERE THE SHAFT IS TWISTED IT IS ALSO WEAK IN THAT AREA. THE SHAFT CAN BE CHANGED ON THE BOAT. IF YOU NEED NEW BEARINGS OR ANYTHING OTHER THAN A SHAFT YOU WILL NEED TO TAKE LOWER OFF, AND GO THRU IT.

You'll want a solid hup prop with the HP. And yes, you must replace that shaft! Any time a twist shows up, it means that the shaft has wrapped up beyond it's elastic limits. Any visible twist would be considered a failure needing replacement. It's total failure is imminent! And when it fails, you'll be shopping for a new prop too! I think that IMCO may have a shaft that is cheaper than the merc piece. You may also want to consider upgrading to the 1.25" shaft.

If that was an IMCO shaft you would be shopping for a prop,there to hard to twist,they just snap off.Go to the xr larger shaft and change the hub on the prop.

If it's twisted, it's bent.
What's the chance of it not having no runnout when it is twisted? My guess is none.

Dave,
I would recommend you change the shaft. If it is bent, that spells trouble. If it breaks, you loose the prop, etc, etc.

There are several options for prop shafts, hardened shafts, larger shafts and the stock shaft. Stock shafts are two pieces welded together and will break. Years ago it was common for cats to break prop shafts, not so much an issue with the newer shafts.
It isnt hard to replace with the proper tools. But I recommend you have it gone through and setup properly. A new crush ring should be in stalled and the bearing preload set.
In other words if you want it to last, have it setup right!! There are short cuts to a long road sometimes!!

Dick