Is my prop slipping or not?

ashedd

Petty Officer 2nd Class
Joined
Jun 16, 2015
Messages
175
I've been looking around and can't really find a description of a spun prop hub that fit's me. I have a '68 Johnson 20hp SS pushing a 14' inflatable. I've been using a 9X9 prop, I do have a 9X10.5 too but it's got a chunk taken out of it, and last time out it started do something odd. I first noticed it while going through a canal(cut) with other much larger boats, the wake/chop in that narrow canal were pretty intense and my motor would rev a little high and we would seem to stop moving. After letting off the throttle a little the prop seemed to bite water again and push us forward. It was slowing us down enough that I had to pull all the way over to the wall to let the other boats get past me. At the time I figured that the heavy chop was causing the prop to surface a little. After the canal we motored around a little while watching the sunset. It was rapidly getting dark and I don't have lights, so I high tailed it back towards the canal to get to open water and my launch area.

On the way back I had the same issues, but instead of an engine rev, which it would do if I added power, it felt like we would stop being pushed by the prop and the bow would rise from the bow wave, then I could feel us getting pushed again by the prop. It would do that a lot. I was able to add some power and get going faster, but still had what felt like slipping. No loud clunks like I think I would hear/feel if there was a gear issue. It got bad enough once past the canal that I had to go along at trolling speeds to make any headway. I was hugging the shore because it was 1030 pm and I didn't want to attract the police with no lights, or get run over by someone else. Finally I was left with the option of swapping props for the bent 9X10.5 in the dark, or trying the only thing I could think of and that was put it in reverse and see what happens. I got good power in reverse, made a full circle with decent power then tried fwd again. This time I was able to make full throttle and get back to the dock pretty quick.

So do I have a spun prop, or a trim issue? I'm on the last peg of down tilt, and going up tilt seems to cause problems. I couldn't get on plane that day either from what I remember. When I felt a slip or the engine rev'd I looked down and the prop was well below the the water.. Last time I tried the 9X10.5 I couldn't get on plane either, but I'm sure I have a trim issue and that prop has a bent blade with a small chunk missing. I would draw a line on the hub and check it after a slip but it's a pain to set up the inflatable just to test for a bad prop, then deflate. I would like to get the prop fixed this week,providing it's bad.

I'm new, obviously..

Thanks.
 

ttankmoran

Seaman Apprentice
Joined
Mar 22, 2015
Messages
39
You need to take the prop off anyway.... swap your spare on, should be pretty easy to tell then if its a trim issue or a prop hub issue, if you dont experience the revving up and not going anywhere then your 9x9 is already off, ready to be repaired and boat still useable.
 

Sea Rider

Supreme Mariner
Joined
Sep 20, 2008
Messages
12,345
Make a hub test and check if already kapput, trim engine to sit perpendicular to boat's bottom.

Happy Boating
 

ashedd

Petty Officer 2nd Class
Joined
Jun 16, 2015
Messages
175
I jumped the gun and took a visit to the prop shop. I'm having the 9x9 hub replaced for about $40 and the spare with the chunk missing and bent blade fixed. I'm still amazed what people want for a 40 year old used prop, I figure I'll keep the props I have for now. I'll report back when I know more.
 
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