Stiff Strb Prop Shaft

[LMBoat]

Hi All,

I need some help. Boat is a ’99 45’ Express Bridge with Cummins 6CTA’s with ZF IRM280VLD V-drive transmissions. All shafts, props, cutless bearings were pulled, checked, replaced when we got the boat 3 years ago. Strb prop has always been a big harder to turn than port. Alignment had been checked then, all good. This was attributed to a differences in the cutless bearings.

Boat has run fine since then, but when cleaning the hull 2 weeks ago, the strb side prop is now more difficult to turn, It takes a lot of effort, and I can’t spin the coupler inside the boat without a wrench. I was assuming the alignment was getting out of whack.

Yesterday, I split the prop and trans couplers (still attached, bolts lose) and checked the alignment. I was expecting the shaft to spin easier when I did this, but nope, and alignment seems to be ok, about .010 out, but side to side not up and down. So, I’m trying to figure out why this shaft is becoming more difficult to spin.

Everything runs fine, I have not hit anything, no vibrations, no other symptoms, etc. In my experience, cutless bearings usually become looser with use, not tighter. Is this accurate? Could this be something in the trans? Any other ideas? Troubleshooting steps?

Thanks for the help!
Larry

 

[480ces]

When it's not connected to the trans how does it spin? How does the trans spin when the propshaft is disconnected?

 

[barlow]

Same problem for me turned out to be a bent strut. Worth checking.

 

[LMBoat]

Thanks guys, it looks like this is the most likely problem, but I don't remember hitting anything that might have caused this. I split the couplers but did not seperate them completely because the boat is in the water and I was concerned that if it is a bent strut, that I might not be able to get the couplers back to gether again, or having an issue with the shaft seal or stern tub, etc. What are the odds of this happening?

 

[peterkvs]

On my 99 400 Sundancer the cutless bearings got tighter with age. When I replaced them this spring they were so tight it took both hands on the ends of the prop blades and a lot of strength to budge them. When I would take the engines out of gear, one of them would squeal. When I replaced them I could easily turn the prop shaft with two fingers. However the cutless bearing was lubed with some soap at that time. Now after 100 hours or so it is still easy to turn with one hand.

When you check alignment you need to check that the coupler mating faces are parallel to each other. They should be parallel to within 0.004" across the face of the coupler. Side to side and up and down is almost impossible to measure in a meaningful way unless you have something to hold the shaft in the center of the shaft log.

Hope this helps,

Pete

 

[LMBoat]

Update: I seperated coupler halves. Trans spins fine. Prop shaft coupler still very difficult to turn. When I seperated the halves, the prop coupler dropped 1/16" of an inch. Is this abnormal or just normal shaft drop? Alignment is still off .022 on side to side. With the shaft drooping, alighnment is now off up and down. It was within .002 up and down when conneted. If the strut was bent, wouldn't that cause the shaft coupler to be farther out of alignement? Could this be just a tight cutless bearing? FYI, shaft seal is not leaking. Thanks for any comments.

 

[peterkvs]

The shaft is supported at the strut end and by the transmission coupling flange. It will always droop when you disconnect it from the transmission if you separate the couplings past the alignment boss.

You measure the alignment by measuring between the flanges, not how they match coaxially. separate the flanges, pull apart slightly, put a .010 shim in somewhere between the flanges, push them back together (no bolts) and then measure the gap all the way around. The flanges should be within 0.004" of being parallel to each other. If they are, then turn the prop shaft 90 degrees while not turning the transmission coupler and make the measurement again. If the measurement changes, then you may have a bent shaft or an untrue coupler face.

Pete