Cavitation Damage on Propeller

[Marley]

I purchased a new Mercury spitfire propeller last June and I am having what I think is cavitation damage show up. Not sure what is causing this, motor is at 5800 rpm WOT. Is there something wrong with the prop itself?

 

[Aquaholic]

All blades? 4 blade prop?

Do you notice any slipping or hear any rpm increase with no speed change?

 

[Corey_lax]

I purchased a new Mercury spitfire propeller last June and I am having what I think is cavitation damage show up. Not sure what is causing this, motor is at 5800 rpm WOT. Is there something wrong with the prop itself?

Height of the motor is probably the best place to start. What’s the prop wash look like when you’re planing? Where’s the plate when you’re planing?

 

[Corey_lax]

All blades or just that one? 4 blade prop?

Do you notice any slipping or hear any rpm increase with no speed change?

You can see it on 2 of 3 blades. So it’s on the other one as well

 

[Aquaholic]

You can see it on 2 of 3 blades. So it’s on the other one as well

Got me before my edit.

 

[Aquaholic]

What is the manufacturer max rpm for the motor? I agree it looks like cavitation, not ventilation.

 

[Marley]

Hi Guys

Sorry I should have been more clear. It is a 4 blade prop and showing up on all 4 blades in the same place. How would motor height affect the propeller? It’s a 2020 90hp Mercury. I believe max rpm is 6000

 

[Corey_lax]

Hi Guys

Sorry I should have been more clear. It is a 4 blade prop and showing up on all 4 blades in the same place. How would motor height affect the propeller? It’s a 2020 90hp Mercury. I believe max rpm is 6000

It might be too high. Get on plane and have someone film the back of the boat. You want the cavitation plate just above the water when on plane

 

[Corey_lax]

Did you have a 3 blade on there before? Four blades provide more stern lift so you’ll be more out of the water than before

 

[Aquaholic]

Hi Guys

Sorry I should have been more clear. It is a 4 blade prop and showing up on all 4 blades in the same place. How would motor height affect the propeller? It’s a 2020 90hp Mercury. I believe max rpm is 6000

I have read that those cavitation marks can show up on high lift propellers, which is what your four blade is designed to do. I have the same propeller in a 17 pitch that I had on a 90 Merc and it didn’t have any of those marks at all.

 

[ship happens]

That's the zinc / trim tab. It's either the wrong one or it's possible it's swung around?

Any pictures of the trim tab zinc and cavitation plate ?

 

[Sr SQ]

That's the zinc / trim tab. It's either the wrong one or it's possible it's swung around?

Any pictures of the trim tab zinc and cavitation plate ?

Agreed looks like a rub not cavitation to me also

 

[Aquaholic]

Agreed looks like a rub not cavitation to me also

Could be but interesting the rub mark doesn’t go all the way out to the edge on that top blade, when the cup in the prop would bring it closest to something leaving a rub mark.

 

[RevyG]

I am having same issues on my 2020 Merc 150, OG Prop and now the new one I put on, trying to figure it out
I will get some pictures as well.

 

[ship happens]

It's hitting the trim tab zinc

 

[Marley]

I looked closer this morning and it looks like there is pitting of the aluminum as well. I will get a better picture and post it. I also emailed M and P where I bought the prop to see if I can get a warranty claim as the prop is less than a year old.

 

[Aquaholic]

I looked closer this morning and it looks like there is pitting of the aluminum as well. I will get a better picture and post it. I also emailed M and P where I bought the prop to see if I can get a warranty claim as the prop is less than a year old.

Can you get a picture of the clearance between the trim tab and the propeller blades?

 

[Marley]

I will also check the trim tab but I think it is clear.

 

[zurk]

doesnt look like cavitation damage. cavitation damage looks like this : https://commons.wikimedia.org/wiki/File:Cavitation_Propeller_Damage.JPG
its an erosion of the surface with bubbles.
you probably whacked a rope in the water and scraped some stuff off your prop. or maybe a submerged branch/log/whatever.

 

[Flashman]

Cavitation is one of the easiest forms of damage to identify. If it's full of little pits, jagged and sharp it's most likely cavitation. Google images of cavitation damage, it's unmistakable.

Would need very close up photos to assess without being there in person. Macro camera settings on a smart phone with good light should be able to pick it up.