Mercury 15hp

[zeus50]

Question.

This happens "some times" i haven't pinned it down yet, but looking to see if you guys with WAY more knowledge may be familiar.

While driving, it feels like my prop is skipping in the water. I knew my prop was pretty dinged up, so I replaced with new one, still does it.

Now it "seems" that if i build up speed gradually, it doesn't happen. I haven't confirmed this just started.

What "could" this be? what options do I have? WHat should i look for?

Thanks,
Z

 

[kofkorn]

Is it a sharp feeling like a "clunk" or a smooth feeling like a loss of power.

Sharp feeling could be a slipping clutch dog. This will tend to get worse over time and will show up more in high power situations (full power launch or running WOT).

Smooth feeling could be cavitation if your motor isn't riding at the right height.

I'd tend to lean toward the clutch dog. Make sure that you are doing quick, strong shifts on your lever, don't try to ease into gear. Try to make sure the engine is at a low idle before shifting. Make sure the prop is going as slow as possible when going from rev-fwd or fwd-rev.

If it is your clutch dog, you'll need to open up your lower unit to inspect/replace components.

Good luck!

 

[zeus50]

thanks for the quick reply. it feels/sounds like a quick rev up. it's more smooth than sharp.

 

[kofkorn]

Can you post a picture of the setup, specifically where your cavitation plate sits in relation to the bottom of the boat? Which hole is the trim pin sitting in? Can you move the pin to a hole that will trim the motor down?

You've already changed out your prop, which should remove the possibility of a spun hub causing your issues.

 

[GYPSY400]

What kind of prop did you replace it with? Was it a Solas two piece?

 

[lovedr79]

Sounds like a bad hub, prolly on its way out. Put a mark on the hub and one on the prop. Run it until it slips. If the marks move you have a spun hub

 

[zeus50]

Here are pics

 

[kofkorn]

Your height looks good, if anything, it's a bit low. Shouldn't be seeing any issues with cavitation at that height. You shouldn't be having any issues with a spun hub, as your prop is new, but as mentioned above, it's easy to determine and you should eliminate that as a problem.

Make a mark or nick on the inside of the prop aligned with the cotter pin or another mark. Run it until you feel the slipping and the re-check. If the marks aren't aligned the same, the hub is slipping and needs to be repaired.

Other than that, There isn't much else that could be happening. Any slipping in the clutch dog or gearing would produce a very obvious sound or vibration.

Are you possibly getting fouled with weeds? Does it occur at a particular speed or boat loading?

If possible record a video when it occurs.

Sorry I can't provide more info.

 

[lovedr79]

clutch dog makes a heck of a racket and so does a blown gear.......