Bad Volvo Penta Props?

Stringer

Idiot Savant
Jul 7, 2005
1,226
234
Bakersfield
Name
Stringer
Boat Name
25 Skipjack FB
Launched out of Channel Islands on Saturday, picked up some decent fin bait and motored out of the harbor. I had just throttled up and was starting to come up on plane when I heard a thud and started getting a really bad vibration. I immediately killed the motor and lifted the outdrive, thinking maybe I missed seeing some debris in the water. Nothing on the outdrive and couldn't see any issue from the angle I had on the swim step, so we donated the fin bait back to the sea and crept back to the launch ramp.

As soon as we got the boat back onto the trailer I noticed that the forward propeller had lost a blade. There was no sign anywhere on the outdrive, rear prop, or other blades that there was an impact of any kind.

Just curious if anyone has ever seen a blade just let go? I'm thinking maybe it was a bad casting, or there was some porosity in the metal?

These props are less than a year old, probably don't have 20 hours on them, and the boat is kept in covered storage when I'm not using it.

The rest of that forward prop looks like it did when I pulled it out of the box. The rear prop though is showing some pitting on all the blades about a half inch out from the hub, so I'm also a little concerned about that. If anyone has some prop knowledge, I'd be glad to hear what you think the issue might be. Thanks


prop.jpg
 
Upvote 0

jiggermyster

Goin' out...
Dec 12, 2003
765
1,414
So Cal
Name
Clay
Boat Name
n/a
That dark area in the middle sure looks like an inclusion.
Also the dark line along the bottom right and at the rear on the left.

fwiw, shiny, crystal looking areas are fresh break. Darker areas are usually where cracks or inclusions have been for a while and have oxidized.
Those areas will also appear more 'polished' as the weakened prop flexes and rubs the surfaces together.

ed: That lower unit looks kind'a crusty. How are your zincs?
 
Upvote 0

Albiebac

Member
Jul 23, 2004
303
121
Scripps Ranch
Name
Eric
Boat Name
25' Skipjack, Albiebac II
The rear prop pitting is due to cavitation, all VP duoprops (Aluminum) do that. >:(
 
Stringer
Stringer
Thanks Eric, I had wondered if that were the case., is there any way to minimize or combat the affects of the cavitation? Or is it just the nature of VP Duoprops? I wonder if it would help to smooth it out a little and re-powder coat them when they start to show heavy pitting, as a preventative measure?
Upvote 0
Upvote 0

jiggermyster

Goin' out...
Dec 12, 2003
765
1,414
So Cal
Name
Clay
Boat Name
n/a
The rear prop pitting is due to cavitation, all VP duoprops (Aluminum) do that. >:(
I'm looking at the lower unit on the right.

Stainless pits too. We'd get surface pitting on the Mercruiser cleavers we ran on this. 'course, they were spinning 8,000 rpm.

ed: nevermind... You were replying to the OP.

ul38vidiot1.jpg
 
  • Like
Reactions: One_Leg
Upvote 0

Stringer

Idiot Savant
Jul 7, 2005
1,226
234
Bakersfield
Name
Stringer
Boat Name
25 Skipjack FB
That dark area in the middle sure looks like an inclusion.
Also the dark line along the bottom right and at the rear on the left.

fwiw, shiny, crystal looking areas are fresh break. Darker areas are usually where cracks or inclusions have been for a while and have oxidized.
Those areas will also appear more 'polished' as the weakened prop flexes and rubs the surfaces together.

ed: That lower unit looks kind'a crusty. How are your zincs?
Zincs are a few years old, but don't see the water that often and have lots of meat on them. you would be hard pressed to tell the outdrive itself from a new one.
 
  • Like
Reactions: jiggermyster
Upvote 0

dctrjayyy

Member
Jun 27, 2005
434
256
44
Tustin
Name
Joshua
Boat Name
whaler
Yes, bad prop. No, the cavitation burn there's nothing you can do. Fyi, your lower looks nothing like a new one in the pic. Looks like the guy said, like it had been in the water without zincs
 
  • Like
Reactions: One_Leg
Upvote 0

Stringer

Idiot Savant
Jul 7, 2005
1,226
234
Bakersfield
Name
Stringer
Boat Name
25 Skipjack FB
Yes, bad prop. No, the cavitation burn there's nothing you can do. Fyi, your lower looks nothing like a new one in the pic. Looks like the guy said, like it had been in the water without zincs
I loaded a pic of the outdrive, you’d be hard pressed to find one as clean.
 
  • Like
Reactions: jiggermyster
Upvote 0