Another boat question

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OK, so boat motor has developed an intermittent issue. When I give it good throttle, it is "slipping". It will move fwd altho slowly.
Ill bring back to neutral, then try again and most times its fine. I decided to remove prop and see if I can detect any damage/issues.
None that I can see, splines good, sleeve(pics 3&4) fits snug in prop.....ideas?
Thanks
Steve

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It's usually the rubber bushing in the prop hub.
It'll take so much power. then slip like a clutch.
You may be able to get it re-bushed, but I had limited success, especially in bigger h/p motors.
Use a felt pen, draw/strike a line from center of hub all the way out to prop.
Next time it slips. See if line is still continuous .
Good luck
 
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I looked for a rubber bushing/coupler in Mercs online catalog. I did see a clutch, #16. I hope it's not that lol.
Inertia said:
It's usually the rubber bushing in the prop hub.
It'll take so much power. then slip like a clutch.
You may be able to get it re-bushed, but I had limited success, especially in bigger h/p motors.
Use a felt pen, draw/strike a line from center of hub all the way out to prop.
Next time it slips. See if line is still continuous .
Good luck
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4spdragtop said:
I give it good throttle, it is "slipping". It will move fwd altho slowly.
Ill bring back to neutral, then try again and most times its fine.
Click to expand...
Steve: before I had my oil canning hull welded up I would suffer from cavitation quite a lot. It’s caused by a lot of different things. Exactly the same symptoms. It’s like you have bite on the water and then it lets go. Slow down and start over and everything is fine.
Look for damaged surfaces on or ahead of the propeller or change the pitch of your outboard even…
 
Thanks Doug, there is slight corrosion/pitting on the prop. So cavitation is possible.
I reinstalled the prop yesterday, ill take it off and investigate a little closer. The black plastic/delrin sleeve slides in/out of the prop(as it should). I was under the assumption that the delrin sleeve replaced the rubber "bushing". There may be one "deeper" in the prop?? The sleeve on mine showed very little wear or cracks/damage.
When I spoke to dealership they couldn't(or myself) get a breakdown of the prop, which they thought was weird??
Here is a video with a very similar setup to mine, altho prop is different, everything else appears the same?
Its a 90 hp mercury efi 4 stroke, s/n 1B285195.
mercury site.
Mercury Marine Parts Digital Catalog


like_A_pike said:
Steve: before I had my oil canning hull welded up I would suffer from cavitation quite a lot. It’s caused by a lot of different things. Exactly the same symptoms. It’s like you have bite on the water and then it lets go. Slow down and start over and everything is fine.
Look for damaged surfaces on or ahead of the propeller or change the pitch of your outboard even…
Click to expand...
 

After some research it appears my issue was ventilation rather than cavitation. The later being the boiling of water in lower pressures around the prop, and the former was an introduction of bubbles into the prop.

Fun fact: cavitation is exacerbated by higher water temps. My worst experiences were in Sam Rayburn lake in Texas. Almost 0 issues in the North Pacific…so far. What’s your water temperature? Change as summer progresses?

Both can result in your symptoms but go away with changing your velocity for a moment.

The usual mechanical suspects seem to be ok. I say keep fishing until the ice cometh…and then tare it apart this winter???
 
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