Stumped on Prop Problem - Carolina Classic

[njfishing]

1999 Carolina Classic. 8.1 jack shaft and a Volvo Penta Duoprop. I keep the boat in a slip here in NJ April - Nov.

Last spring when I was getting the boat ready to launch I noticed the aft prop (aluminum B6) had some pin holes that bore through the blades where the blade curves to meet the hub. Got a brand new set of props and the same darn thing happend.

Anyone have any ideas as to what could be causing this ? I was thinking maybe cavication burn but there is nothing forward of the drive like a transducer to cause bubbles. I'm also thinking it could be galvanic corrsion or electrolysis but if that were the case I'm thinking both props would have had similar pin holes but it's only the aft prop.


Some additional info... I change the zincs at the beggining of each season. The zincs are usually pretty well shot when I pull the boat for the season. I don't have shore power or a battery charger.

Any one have any ideas as to what might be causing this ? I was thinking of going to stainless props but the people are Carolina Classic advise against it because of electrolysis problems.

Thanks for the help guys. I'm tired of spending $700 bucks for a set of props every year...







some bad rops I've had to replace

[auguste]

There was a report of similar problem with Mirage ? boats and they tied it to galvanic corrosion

I understand that the aluminum props are also prone to cavitation decay . . . but I don't know if that is your problem

When I got my 2 Volvos 18 or so months ago the service guy said that he would prefer not to sell me the aluminum props, wanted me to get the stainless . . . they charged me less than $100 per set . . . they apparently didn't want an issue

Sorry, but I do not possess more specific answers HOWEVER under the forums you will find SHIPYARD INDUSTRIES MARINE . . . SIM is a good fellow and he knows his Volvos . . . ask him the question

[backman]

check your bonding strap and make sure all thruhulls; shaft, rudder, and tab's are connected via the green wires to the copper bonding tape running throughout the boat.

Does your boat run down the batteries over time if left off? Do you have a radio wired off the main switch? Minje (98 CC28) had a ground leak which was a design problem where the #22 gauge wire to the radio circuit came off the hot side of the main switch and over time bled down the house side of the batteries - that ground leak to an unbonded thruhull such as the outdrive could cause the pinholes.

Call Mac and ask about ground leaks....

[njfishing]

Thanks for the replies guys. I'm beginning to lean more towards electrolysis because the issue with the prop seemed to coinside with problems we are having with the house battery holding a charge.

This issue came into play after our 7.4 motor was replaced with an 8.1. I'm wondering if some of the wiring was disruppted in the process of swapping the motors.