Leaking sd60 saildrives

[Captain Bill]

Last year while my transmission section of my two Yanmar SD60 saildrives were being replaced due a manufacturing defect I decided to have my prop shaft seals replaced because I was pretty much at my two year scheduled replacement. The mechanic noted that I had nearly 1200 hours on the drives and that there was a bit of a groove worn into the prop shaft by the water seal and the oil seal and it was not unusual for them to wear enough to start leaking at the 1400-1500 hour mark. He recommended speedy sleeves as a solution. I know there is another thread discussing how to repair prop shafts but my questions are a bit different and I don't want to hijack that thread. I went to the Bahamas this winter and the winds were adverse or non-existent so I ended up doing more motoring than usual and put about 400 hours on the engines. All was going very well and I last checked the drive oil in Cumberland Island GA. We mostly sailed up the GA coast and did some motor sailing to Charleston where we bought fuel and ducked into the ICW to Georgetown SC. We spent the night there and sailed to Beaufort NC on the outside up to Oriental. When I checked the oil in Oriental it looked like a chocolate milkshake in both saildrives!! The oil level was also well above the full mark. My question is not is there water in my saildrives, I know that. My question is why? There was only about 15 hours difference in the drive hours so something very strange happened between Cumberland Island and Oriental. I am now on the hard and have drained both drives and removed the seals an prop shaft from the starboard drive. The speedy sleeves have an obvious polished area where the seals ride, but I would not call the worn. I examined the seal surface with a 10x magnifier and can find to nicks, cuts, or signs of abrasion. When I got the shaft out there did not appear to be any water between the seals though there was a little bit of "crud" between the seal riding areas on the shaft that appeared to dry and was similar to encrustations outside of the seal. The O-rings on the bearing/seal carrier were also examined with the 10x magnifier and no nicks, cuts, or any signs of leakage could be found. The Oil plug O-rings were intact and the plugs tight. The only other place I know of that could be leaking water into the oil are the O-rings between the upper case and the lower case. These seals do not move and my experience with o-rings is that if nothing is moving they either leak immediately or they don't leak. I have to pull the sail drives out of the boat to check those O-rings and am reluctant do so as an early step. I intend to replace the oil plug in the port drive and pull a vacuum inside it and see if I can tell where it's leaking. What really has me stumped is that they failed basically at the same time. The only thing unusual that happened was that I did run the both wide open for about 15 minutes to make a bridge opening in the ICW. My first thought was that I ran over some mono-filament, but there isn't any on the shafts and I've had that happen before but never on both drives. That kind of damage doesn't take a 10x magnifier to see. I'm looking for any ideas on what could have happened to both drives to make them leak. Help please.

[belizesailor]

Ive had the odd random leak on sail drives, often after putting new shaft seals as the wear in, but never 2 at once...though they were changed at the same time. My experience has been that the one time leaks after changes may resolve themselves, but they usually happen almost immediately after changing...you had put a lot of hours in on these right?

Given that you dont see any obvious problems, I would pressure test the drives and if no leak found close 'em back up and see what happens. Maybe it was the short WOT run. I agree, I would not pull them to check the unlikely posibility that water somehow got in around the upper seals.

[Captain Bill]

I have just started the vacuum test on the port drive and it looks like the pressure is not holding. I put a drop of oil around all the connections to the vacuum pump and none of them have been sucked in so my pump connections don't seem to be leaking. I'm down about .5 inches of mercury in 5 minutes. Now I have to figure out where it's coming in.

[NoTies]

I would definitely be looking at the small O ring for the oil passage where the drive splits in 2. It is awkward to do but you can separate it with the drive in situ if you use a long 3/8 extension, universal and in-hex socket. In saying that, the chance of upsetting the O ring during reassembly is higher if you use this method. There may well have still been an air pocket in the saildrive aperture which eventually worked its way out after a while.

[belizesailor]

I think if I decided to split the drive leg that I would just pull the whole drive...its not that hard. Working thru the aparature in the hull to reassemble the split leg seems like it would be very difficult & error prone.

[NoTies]

There are some trade secrets that make it a lot easier.

[Captain Bill]

The pressure dropped to 3.5 inches of mercury from 7.5 in about one hour and 20 minutes. I had my hopes up but a friend just pointed out that such a slow leak might be coming past the input shaft oil seal as it is designed to keep pressure in, not out. So much for my great idea. I think a pressure test might be in order. An O-ring would leak in both directions and the input shaft seal should hold pressure from the inside. I could also put the foot in a bucket of water and watch for bubbles. I have taken sail drives out before and do not look forward to the possibility that I'll have to do that, but I don't see a practical way of splitting the drive and reassembling them through the bottom of the hull. Accessing those O-rings would be difficult at best and completely in the blind.

NoTies, I see you are a marine service provider. Do you have experience with problems with the oil passage O-rings? You can PM me if necessary.

[NoTies]

The oil passage O ring sits in a shallow recess and I have had to rectify a leak once where it was displaced during fitting by someone. Fortunately it became obvious as the O ring was split in 2 and the boat was still on the hard so oil was seen escaping.
In hindsight this is possibly more likely to happen with the drive out of the boat unless a suitable jig is available to keep everything vertical when fitting as most people seem to pull apart and reassemble with the drive on its side (which allows gravity to do its thing). I shouldn't really give away trade secrets but there's nothing too technical about my methods. Firstly buy a couple of lengths of threaded rod (8mm from memory) and wind them into opposite bolt holes to act as a guide and secondly have a prop long enough to hold the lower half firmly up against the upper half when in place to allow for bolting up without having to bear the weight. I find the long extension with integral universal on the end to be more manageable than an extension plus universal.

[Captain Bill]

I'm afraid the opening in my hull is not wide enough to access the O-rings from the bottom as there is no way for me to get my hands past the flange with the drive hanging in there. I would need to enlarge the hole in the bottom to drop the drive leg through it.

[NoTies]

I would be surprised if this was the case as the lower unit flange is quite small in diameter. I have seen drives fitted by splitting in 2 and fitting the top from inside and the bottom from outside instead of shifting the engine or because a bulkhead was too close to allow sufficient tilt to fit from inside.

[Captain Bill]

I did the pressure test and the drives are tight under 7.5 PSI overnight. If it was an O-ring it should have leaked in both directions. One other possibility I have been discussing locally is that the prop shaft could be bent or out of round and leaking at high rpms because the seal could not follow the eccentricity. I just eliminated this by taking the shaft to a machine shop and having them tested for being bent or out of round. The shaft was true to .001". The machine shop specializes in marine work and the guy there told me that excess vibration can cause shaft seals to leak. My engines do vibrate quite a bit especially at certain RPMs. I've been trying to track down the source of this for some time. It was worse after I replaced the SD40s with SD60s. Last fall I had the engine mounts replaced and the props sent out for refurbishment at a reputable prop shop. No change. I,m open to ideas about what to do next.

[NoTies]

Damn, it would have been nice to isolate the problem. I have on occasion (but rarely) seen shaft vibration lead to an oil leak via the shaft seal. I don't think this would come from the engine as the problem seems to be concentrated close to the source of the vibration so, as you are getting water ingress it is more likely to be prop vibration. Checking runout of the prop hub with the prop fitted would be a good place to begin.

[Captain Bill]

Well, as I grasp at straws, I've been researching causes of vibration and come up with a new theory, which may or may not be as good as my previous theories. There is a possibility that the vibration is caused by cavitation. I've had an excess vibration issue for some time as I stated earlier. The SD60 saildrives have a higher gear ratio than the original sd40s so the props turn at a higher rpm than they did in the sd40s. I adjusted the pitch following the prop makers instructions when I had it on the sd40s which increased the pitch a bit over the previous settings. There was a little bit more vibration at that time, but tolerable. The vibration increased substantially when I put in the sd60s. Especially under high loads, but not so bad at moderate cruising speeds. Cavitation is worse at high prop loads and when I was running at full throttle in South Carolina The props were definitely loaded. I think I will put the drives back together and reduce my prop pitch a bit and see if that solves my vibration problem.

[Thumbs Up]

Simply overfilling the oil level can cause them to draw seawater in past the seals as they cool off. I think it is better to keep sail drives filled to the minimum mark rather than the max. Having less air and more fluid creates a more powerful suction as the unvented case cools. You can also buy time on leaky seals by loosening the dipstick immediately after shutting down. (leave your engine key down there as a reminder though)

[Captain Bill]

I have now completed reassembly of both drives. There was no apparent reason for the leak on the starboard drive, but the source of the leak on the port drive was quite clear, the Speedi-sleeve installed last October had cracked completely through and came off with the bearing carrier. It was not a fresh break caused by the disassembly process as the crack was coated with a bit of crud. I carefully examined the shaft and found no detectable wear under the Speedi-sleeve. Last year the mechanic had taken the drives to his shop to replace the failed upper halves and I took his word that the shafts were worn and needed to be sleeved. I'll never do that again. There was a polished line where the seal made contact, but no measurable wear. I replaced the seals on both drives and reassembled them. I pressure and vacuum tested the drive and both held pressure and vacuum. I rotated the prop shafts by hand under pressure and vacuum by hand and nothing leaked. We splash this afternoon and we'll see what happens when I put some serious RPM on them.