Cut The Old Shaft Out
If you know the shaft needs to come out why risk damage to the gear box or gear box flange by trying to press the coupling off the shaft. It is far easier and far less time consuming to simply cut the shaft out. This took all of about 45 seconds to free the 1″ shaft from the flange.
WARNING: NEVER, EVER, EVER, EVER use a “Slide Hammer” to remove a shaft from a coupling if the coupling is attached to the gear box. If you want to throw 3k out the window feel free to use a slide hammer, if not, use proper procedures for removing the shaft from the coupling such as a coupling press tool.
Only sub rate hacks, that don’t care about your wallet, your boat or your gear box, use slide hammers to remove prop shafts from the couplings when the couplings are attached to the gear.
Yes using a slide hammer is quick & dirty, and the damage to your gear box can largely goes unseen, for a period of time, but PLEASE DO NOT be fooled by hacks with slide hammers and do not allow a yard to use one on your boat.
Would you go to a dentist who used a Milwuakee Sawzall on your teeth? Sounds extreme, but this is about the same level of stupidity as using the wrong tool to remove your prop shaft..
A slide hammer is essentially a long piece of metal bar-stock that threads onto your shaft where the prop nuts go. It is about 4 feet long and has a heavy metal weight on it. The weight is slid up the bar to the prop shaft and then thrown down the bar until it hits the end and SLAMS to a sudden stop. The idea is that it breaks the coupling from the shaft when the weight comes to the sudden and abrupt stop. The reality is it destroys gear boxes in the process.
This destruction of your gear may not be readily apparent so the hacks who use them assume they get away with it and it “works“. Yes it works, it works to DESTROY gear boxes. If your boat yard tells you “we do it all the time” please do yourself a favor and find a new yard.
Slide hammers can cause brinelling of the bearings or races in the gear box. Brinelling means the shock loads imparted on the static bearings, by the “slide hammer“, create FLAT SPOTS or DIMPLES in the races or bearings. The gear may work for some time after the slide hammer event but eventually the damage rears its ugly head. The damage is often never attributed to the slide hammer and this is a mistake as the slide hammer started the failure by brinelling the bearings or races..
An Ouch Moment:
About twelve years ago I was at a yard when I overheard the summer help yard boys slamming & slamming & slamming a slide hammer to free a shaft from a coupling. All of a sudden I heard one last SLAM, then a clunk and the sounds of metal bits on fiberglass, then I heard;”OH SHIT!!!!!!“……
You guessed it, they hit it so hard they blew the case of the gear box apart and destroyed it. The slide hammer literally cracked the iron gear box wide open. The shaft, after all the beating that finally destroyed the gear box, was still firmly embedded in the coupling.
Rant over…. Please use common sense…