Just to be clear, we are talking about Volvo folding props and Volvo saildrives? My response below is based on this.
We just replaced a folding prop because of teeth wear. The old prop was 11 years old and had 1700 hrs on it. I think a contributing factor was my having the yard sandblast it to remove the old primer and paint. I didn't notice the worn teeth when I gave it to them (and the prop worked fine) but there was significant loss of metal and pitting on the teeth after and the prop blades would slip when opening/closing and not work properly. I know of two other boats with worn prop teeth after ~8 years and many hours, but one was directly contributed to stray current in a marina (lots of damage besides the props).
The saildrives and folding prop combination have been in use together for many years across the globe without incident, and the props have also been used on Yanmar saildrives, so I don't think the props are responsible for the transmission damage. More likely is that the blades did not open evenly because of the worn teeth and the resulting unbalance did the damage. If this was the case, I would expect water in the oil due to worn lip seals and possible bearing damage. Or gear damage caused by these. What type of damage did you find?
I agree it shouldn't be happening with the age of your props and number of hours. How did you rule out corrosion? Can you post a picture of the gear teeth?
Go to their Blog www.Mahe36.blogspot.com, it is a great read, and they are a very interesting couple. Sorry to see them leave the thread. I'd also suggest Lonnie and Terri's web site, another adventuresome couple WWW.pgacouple.com
I agree with Colemj about stray current in a marina making your props wear prematurely.
Here are other possible causes:
1. Stray current in a marina
2. Prop Zincs worn prematurely
Even though your sail drive may have good Zincs, your props have a Nylon Isolation ring that keeps it electrically isolated from the Sail drive, so this makes having good prop zincs very important
3. Gears not greased (Yearly)
4. Each blade is numbered 1, 2, 3 and must go into hub space 1,2,3 if not they will ware unevenly when placed in the wrong hub location
5. To much barnacle growth grinding in the teeth
This is not likely, this bronze is very hard. I used a file on it and had a hard time removing any metal
Attached are pictures of Blade gear teeth after 7000 miles they still look great.
Note: the best way to extend zinc life is to paint your props (Not with bottom paint with copper). By painting your props you give less electrical contact with the water which will make the zincs last longer
Lori, Mark, and the other Mark,
Galvanic corrosion by stray currents may not be the cause in my idea, since the sail drives and the propellors are isolated from shore power ground and boat 12V ground. There is a plastic ring between engines and sail drives.
Our folding propellors are very good after 7200 miles. The zinc anodes of April 2009 were almost totally gone 3 weeks ago, I replaced them and are worrying about the cause of the fast wear. Bad zinc quality? Coppercoat?
Because of this fast wear I have been considering galvanic isolators, however seeing the sail drive isolation this might only protect the aluminium rudder shafts.
Kind rgds, Jef
Good news for Oceanview, F-P and the manufacturer of the Trampoline have agreed to replace my damaged one. The best I can tell is the netting has not been treated or just marginally treated for UV protection, the tears are occurring along the edge were the load is greatest, if you step right at the edge. I now make sure that I step well past the edge to distribute the load more evenly. I have to say the netting looked fine before the rip(s), until you get down very close and inspect them, you can see fraying starting with little "hair" like fibers sticking out from the webbing.
Keep an eye on this, don't want to see anyone getting wet (unless they want to ).
You can replace the Hepworth red or blue water pipes with Whale 15 mm pipe and fittings, which is readily available (even at West Marine). The Whale product has much thicker walls and will hold up better than the original piping, also the push on connectors are much easier to use and, I believe, better than the threaded connectors. Also the Whale push on connectors fit the Hepworth piping, so it is easy to retrofit. Used it while plumbing the water maker. Just my 2 cents worth.
After having sailed this week end mostly downwind,I realize that it would be really fun to have a light air headsail on our Mahe. Without spending a fortune I would like to pick your brains and get some ideas from all of you.Some thing easy to set up that would really make a difference down wind.
Thanks to everyone for the very usefull informations on the last posts.
The cheapest and easiest would be a assymetric chute in sock using a bridal for the tack point. I use this setup on a 44 foot cat and it works great. Used chutes can be found on Ebay or from several used sailmakers for very low cost. You can fix up a bridal on the bow quite cheaply. Then you only need a snatch block for the sheet. You can even use only one sheet and simply jibe the chute by snuffing it and move the snatch block and sheet around to the other side.