SD50 - Life Expectancy

Intentions are to write-off the monies spent of maintaining the wretched thing (about £5k the past two years) and go for a new or reconditioned SD60 which I can source for about £4k plus fitting/VAT.  

I'm told that 17 years and 1500 hours of use is 'old' and 'very much' and that its no surprise that the leg is failing.  Given the number of such legs in use that surprises me a great deal and I'd be interested in the experience of others with SD50s.  Any views on if the mechanic should have been able to spot the wear given the number of times he's worked on it?

If you can't take a joke - don't buy a boat!

Iain

Since posting the original I'd been toying with the idea of delaying replacement for another season by which time we plan to be in the Clyde area.  However, the Mechanic had been concerned about chards affecting the upper section so your advice about the the magnetised plug is useful in itself.  Thanks also for your explanation of what the picture shows; by itself it meant nothing at all to me!

Iain

no trouble doing the oil change while afloat.  In case it's not too obvious, just need 2 of the (reassuringly expensive) Yammer oil extract tubes in place.  One at the base as normal and another at the alternative connection near the filler cap.  I have the top one permanently connected to a small oil reservoir anyway.  With the drive as warm as possible, put a decent oil extract pump on the lower tube.  Then use a small tyre compressor to pressurise the top of the SD50 gently.  It's never a quick process but I get >2L out in 10-15mins when the drive is warm.  Can take 30 mins if the drive is cold but can still be done.  Easy enough that I do it a couple of times a season (I do that as the GL4 is kinder to the cone clutch but I'm not as convinced of its ability to manage any small seawater ingress (versus the GL5) via the oil seals as they and the propshaft age).

Best of luck with the gears.  Personally, I'd also just go into a phase of refit and monitor.  It's not hard to get the bottom leg open to take a look at oil seals, shaft and lower gears.

Mark

The situation is completely different for saildrives and outboards where the gearbox is immersed in water and they don’t have breathers. Firstly the heat build up is significantly less and consequently the pressure build up is also considerably lower so oil retention at seals and gaskets is more easily achieved. But once the seals have wear on them they do leak small amounts of oil and when the gearbox cools down after use there is also a small amount of water drawn into the gearbox which in turn causes the oil to turn milky. It is remarkable how tolerant gearboxes are to emulsified oil, but the situation needs to be addressed before it gets too bad. The reason that these marine gearboxes are sealed is for the situation when seals are starting to weep. As a sealed unit the boat is still water tight. But if there is a breather fitted, when the seals weep the boat has a leak and if left long enough the water will continue to fill the gearbox and the oil will flow out of the breather until such time as there is no oil left and water is flowing out into the boat. If the breather is fitted and raised to be above the waterline, the gearbox will still take a considerable amount of water before the fluid equilibrium has been reached. In this situation there will be an additional 250 - 500ml of water in the box. Too much for the oil to emulsify and still work which results in a lubrication failure and scraping the internal gears and bearings. 

To summarise, I personally wouldn’t recommend having a breather on a saildrive or outboard gearbox for the reasons outlined above. Just keep an eye on it when doing your engine checks and if the oil is a bit milky, don’t worry too much about it but take a note to change the seals at the end of the season.

Hope this was useful 

Simon