Lasdrop Shaft Seal Failure

actually it is pretty clearly oxygen deprivation if you have seen it. Electrolysis generally has more longer, streak like pitting and less of a somewhat uniform pitting like this.

I agree, I had never heard of the shaft rotation thing either and hence why I missed it. It's literally the last sentence in the manual. They don't specify if just turning the shaft with a wrench is acceptable but I'm thinking not. I would want some water flow to them as well which means starting the engine.

Lasdrop called me back after my conversation with them and said they really want to see the failed components. I will send them to them and let you all know what else they say. And, of course, I'm contemplating if I want to go with a different type of seal in the near future. This whole experience has shaken my confidence in a component I should not have to worry much about.

The only reason I chose the Lasdrop seals over the PSS was because I liked the dual water cooling ports of the Lasdrop. This makes it very easy and neat to run a crossover line so you get cooling water to both shaft seals when only running one engine. Hindsight being 20/20 I should have factored in that when only running one engine I'm going slow enough that the seal is getting adequate water through the stern tube and doesn't really need injected cooling water. Alternatively, I could have installed Tee's in the cooling lines to allow for a crossover. I'll see how these Lasdrop seals hold up going forward and decide if I need to make a change.

Boat went back in the water this morning. So far, all good with the replacement seals. Neither leaked a drop. We also verified that both are getting ample water flow to them from each engine. Time will tell I guess.

The spring and a few other parts are not exposed to air in the engine room, they are contained within the seal area. The cooling water hose barbs are installed into the carbon graphite housing and no contact to stainless. I’m not aware of any other bronze.

Putting that aside, you all raise very good questions, similar to mine. And the main issue I can’t seem to understand is, if this were oxygen deprivation, why didn’t it happen to both seals? The Stbd side looks like brand new inside. Both sitting for same amount of time, in same water, etc. Could it be electrolysis on one side only; sure. But all four shaft zincs (2 per shaft) were worn as about exactly as one could hope for.

It is certainly possible this is a matter of poor material quality. Both the port and Stbd seals are going back to Lasdrop. It will be interesting to see what they say but I’m not holding my breath.

Following up on this issue. I sent the failed seal back to Lasdrop for their input. They inspected and said it is apparent the seal overheated. I was confused on how it could overheat given their are water feeds from both engines. Through several conversations with Lasdrop we determined my seals are plumbed incorrectly. This is a bit frustrating as their are no plumbing instructions in the installation manual. Each seal has two cooling ports. So we plumbed a hose from each engine to one of the ports on the seal on the same side. Then we put a crossover line between the other port on each seal. The thought was if only one engine was running water would flow from one seal to the other side. According to Lasdrop, we need to plumb a line from one engine to seal on same side and install a tee then run the tee line over to the other side and vice versa. So each seal gets supply from both engines.
I understand the concept the way they have explained it but still not clear what caused the overheat regardless. The only time I have run one engine only was slow speed trolling at around 2 knots. At this slow speed the seals should be flooded through the shaft log regardless of water from the engine. The only thing I can figure is somehow that crossover line created some type of unexpected pressure differential issue and perhaps kept the port seal from receiving adequate flow. There is also some evidence that we already have a similar issue on the port seal we just replaced a short time ago (ugh!).
So we will modify the plumbing according to Lasdrop and monitor the seals, including with a temp gun at cruise (which we did after we replaced last time). I will also pull the port seal again at next haul-out to inspect and possibly replace it if needed.