Yanmar SD50 Forward Seal Service Interval and Engine Rear Seal?

[cdiversions]

My Lagoon 400 has Yanmar SD50 saildrives. The survey showed gear oil leakage, which the mechanical surveyor attributed to the forward seal of the sail drives. My engines are about 7 years old (2010 model boat built in late 2009), and have about 850 hours.

I have two questions:

1). What is the service interval for the forward seals of the SD50? I didn't see this as a maintenance item in the operator documentation. The closest mention was to check for oil leaks periodically. The boat yard says the service interval is 6-7 years, so I should go ahead and service both.

2). For people who have replaced the SD forward seals, have you also replaced the engine rear seals at the same time? The yard is recommending this also, since once the engine and the sail drive are apart for the forward seal replacement, the engine rear seal is a small addition.

Note that only my starboard side has gear oil from the sail drive leaking, not engine oil. So far, my port side is totally dry.

Thanks,
Tom

[Dulcesuenos]

Just did it on a 2gm20 with SD 20 may as well kill 2 birds with 1 stone, SD seal was rock hard

[a64pilot]

I do not and have never had sail drives, but it sounds like you have a good yard that is giving you good advice

[cdiversions]

I went ahead and authorized the yard to change the SD forward seal as well as the engine rear seal on both sides. They reported that starboard was leaking gear oil due to the SD seal and port was leaking engine oil from the rear seal.

[boatbod]

If the SD input seal was leaking oil, I hope the yard inspected the input shaft for wear? The last one we did was grooved pretty badly and had to be "fixed" with a speedi sleeve. (New shaft was also ordered from Yanmar, but naturally it was out of stock and had to come from Japan).