The Boating Forum - What bent my prop shaft?

I swapped props for opening day from my factory 3 blade Suzuki prop to a four blade PowerTech on my DF300. Second day out and I hit rocks in the channel leading into my marina. I don't think it was too bad as I was idling into the marina off plane in a no wake zone...I've whacked my Suzuki props several times over the years as bad or worse. The worst blade is pictured below....

http://albertan.smugmug.com/Other/Warrior-V-2121/i-5t3SMx5/0/L/IMG0454-L.jpg

I pulled out of the water to take it back to my cabin to put the original prop back on. I couldn't get the Suzuki prop on for the life of me. After a few minutes, I paused to assess the situation and found the splines on my prop shaft to be slightly bent...

http://albertan.smugmug.com/Other/Warrior-V-2121/i-L5cBcs5/0/L/IMG0467-L.jpg

I couldn't figure out how this would have happened until I pulled out a tape measure and started measuring the splines on the prop shaft and the two props.

1) Prop shaft - 2.5" spline length

http://albertan.smugmug.com/Other/Warrior-V-2121/i-fF2W9WF/0/L/IMG0466-L.jpg

2) Suzuki Prop - 2.25" spline length

http://albertan.smugmug.com/Other/Warrior-V-2121/i-p67RzH3/0/L/IMG0474-L.jpg

3) PowerTech Prop - 1.25"spline length

http://albertan.smugmug.com/Other/Warrior-V-2121/i-DMRHzKH/0/L/IMG0462-L.jpg

So I'm thinking the prop shaft splines are twisted because the PowerTech prop only engaged half of their length. So then my question becomes did they twist when I hit the rocks or just from the torque of the motor? I would assume the rocks, but I had other issues with the prop as well. It cut into my lower unit as shown below, even though it seems fine when I fit it initially.

http://albertan.smugmug.com/Other/Warrior-V-2121/i-W4cqR6Q/0/L/IMG0471-L.jpg

http://albertan.smugmug.com/Other/Warrior-V-2121/i-jFPCqxW/0/L/IMG0469-L.jpg

Mind you it did always sit really, really close to the lower unit case...

http://albertan.smugmug.com/Other/Warrior-V-2121/i-GMDMDBn/0/L/IMG0459-L.jpg

I also had my boat shut down around 5700-5800 rpm, even though the rev limiter is at 6300 rpm. I'm not sure what that was all about as I never had a chance to look into it more closely.

Thanks for any feedback and suggestions. I'm not mad at PowerTech or the company that sold me the prop. Just trying to get some answers so the boats not down if I run the prop again.

What thrust washer are you using with that prop?

You should have got a thrust washer from powertech that came with the propeller.

That prop should not hit the gearcase like that.

There is a washer missing most likely still on the old prop

I sent you a PM. I have a brand new shaft for the std rotation lower unit that I ordered by mistake.

Definitely the right combination of thrust washers and prop nut washers are critical. Surprised to see only a partial engagement of the splines. The engine manufacturer makes them that long for a reason.

I used the parts that were shipped to me by PowerTech with the prop. I also took pictures to confirm assembly with the vendor who sold me the prop. There isn't a thrust washer made that will change the fact that the PowerTech prop only has a little over an inch of splines engaging the shaft. But I'll discuss that with them as well when I contact them. I'm just trying to get some opinions from people with more knowledge than myself.

Just as an aside, this is a picture of the Suzuki thrust washer, with the arrow pointing to it, and the PowerTech washer sitting on top of it. They look completely different. But then the hubs on the two props are completely different spacing-wise as well.

http://albertan.smugmug.com/Other/Warrior-V-2121/i-ZQZsTLc/0/O/PTCLWasheronMotor-M.jpg

And a picture of the PowerTech bolted on. Doesn't look out in left field to me. A larger thrust washer would have resulted in the prop nut being off the shaft/beyond the hole for the cotter pin IMO.

http://albertan.smugmug.com/Other/Warrior-V-2121/i-DKpxdk8/0/X3/IMG0461-X3.jpg

In that picture, you have both thrust washers on the shaft.

When you actually installed the prop, did you take the suzuki thrustwasher off first, or did you use the both like in the picture?

Oh how I long for the days of standardization.

Won't happen in my lifetime however.

In that picture, you have both thrust washers on the shaft.

When you actually installed the prop, did you take the suzuki thrustwasher off first, or did you use the both like in the picture?

I popped the old Suzuki thrust washer off (the one the arrow is pointing to). That is a picture I sent to the vendor to confirm that I was mounting it up right. To be honest there is only one possible combination that would let the prop bolt up. The PowerTech thrust washer replaced the Suzuki one on the inside. On the outside, there was a large Suzuki washer that engages the splines. That was left off and the factory Suzuki washer and prop nut were then used. There was a picture that came with the prop. I'll see if I can post it up later when I get home. Definitely not bolted up with both thrust washers on...the prop nut wouldn't have had any threads on the prop shaft sticking through the hub to engage.

That power-tech is a very heavy prop which is good for high hp motor performance. The damage on the prop indicates a very hard hit. This result is a risk that is inherent with heavy props. Not long ago I saw a 50 merc with a 4 blade ss prop that sheared the drive shaft when it hit a trap in the river....the drive shaft didn't like the sudden stop.

You hit rocks and your asking what bent the shaft???

You hit rocks and your asking what bent the shaft???

Yup. Because I've hit rocks harder with my Suze props and never had this issue.

And really, I'm fine with the explanation that the rocks twisted the splines. Still doesn't explain why the thrust washer and other parts were installed exactly as described by PowerTech and the gear case got chewed. Got an explanation for that?

Were your suki props aluminum?? Steal props have no give like the aluminum ones do. You hit something with a steal prop and your likely to bend a shaft.

Were your suki props aluminum?? Steal props have no give like the aluminum ones do. You hit something with a steal prop and your likely to bend a shaft.

Can you even get aluminum props for a 300? I was told you couldn't when I started shopping for replacements.

Definitely the downside of SS props, they show no mercy if you hit something hard. I bounced off rocks a number of times with aluminum with damage only to the prop, not so much with the SS.