What would cause this? Sportmaster drive shaft spline notch. .

[Pachanga_rick]

2.5 ... just noticed this.

[Frank Molé]

crank might be a little worn

[Euroski]

Ran without the correct grease on shaft.

[tunnelmike]

If they are all like that I agree with wear in the crank.

[outasite]

If your on a cut mid.It was was ether not lined up properly,was not welded so it is flat,or both.It is amazing the mids that are cut and welded that are not STRAIGHT AND SQUARE.Thats what gives them a bad reputation,and causes them to crack.The other possibility is a motor that idels hour after hour without any lube at the shaft.https://www.yahoo.com/news/m/a0d398c...rce.html?nhp=1

[stoker2001]

what about the neutral-drive drop at 2500RPMs or more?

[89LASER]

Not backing out of the throttle when jumping waves/airborne. Check your gear oil for metal.

[Onetime]

Not backing out of the throttle when jumping waves/airborne. Check your gear oil for metal.

There's the correct answer. Very common on offshore boats with a lot of throttling and air time.
JMO

[bigboy]

If 15" shaft possibility that shaft has been shortened and resplined but not hardened again....

I have two shafts like that.

[Tom Foley]

Stainless shafts will do it with an older crank . run it .

[David Borg]

Not backing out of the throttle when jumping waves/airborne. Check your gear oil for metal.

I agree with above statement. I have seen quite a few that way ,here we all boat offshore.I have also seen twisted propshaft splines

[HStream1]

The wear is consistent the whole length of engagement so its not an alignment issue. if it was alignment the wear would be skewed. Looks like lack of Grease to me. Possible no grease was applied when lower was dropped and serviced or carrier seal i.e. (Crank seal) isnt installed or is bad allowing grease to sling out. That shaft is factory and never been cut and resplined so thats not in the equation either.

Make sure the Crank seal is installed and not damaged. Apply a liberal amount of grease" And Like Tom said "Run it".

[outasite]

There is a difference between not flat,and not lined up.Not flat will wear splines askew.Not lined up will constantly walk the spline to one side,causing it kinda roll in and out of every tooth,wearing hard on the leading edge.A working spline,properly lined up,such as used in a Merc application needs virtually no lube were it not for water intrusion,the seal and grease is more to keep water out,and protect the parts from rusting,rather than lube for the spline.JMO

[WillySteve]

Just my 2-Cents on spline wear....ANY Spline!!
Working in drive line related repair for 50ish years I have always noticed those with wear and those without! IMO shafts that are constantly being loaded and unloaded will Always show much more wear than shafts that are just loaded for long durations, whether it be in a boat gearcase or a bull dozer!!!!
Take a vehicle with an automatic trans, or a boat under normal cruzing....the splines are loaded, (on the one side), when it's shifted into gear and stay in contact and loaded until it's out of gear or the direction changed. On a Standard shift, (or a boat surfacing in waves), the splines are loaded, unloaded, and then reloaded with each gear change or wave hit!!!
I can assure you that any standard shift vehicle will show 10 or 20 times, (OR MORE), the wear on any spline than the same vehicle running an automatic, with the same mileage, EVERY TIME!!!!!
A spline on a steel shaft does not know where it's installed but certainly knows when it's constantly loaded and unloaded....the wear comes with the initial contact!!!
Cheers!