Yanmar SD50 saildrive oil leak?

[Skylark]

I hadn't used my boat for a couple of months. It remained tied alongside its pontoon finger berth. The week before last, in preparation for a 35 mile journey from marina to hard standing, I checked her over and found that the saildrive had lost oil. It needed about 350ml to restore the level. A week later, just ahead of the trip, I checked again and it needed another 100 ml.

Now in her cradle and with the flex-o-fold prop removed there is no evidence of a leak around the bottom drive shaft or around the drain plug. After this journey, about 4 hours of motoring, I'd estimate another 1-200 ml loss of oil. Hard to be sure but by examining a "dipped finger" of the oil it does not appear emulsified. There's no evidence of a leak inside the hull / engine bay.

Anyone experienced similar? Any ideas of what's going on, more importantly, what's involved in fixing it?

Boat is 2 years old, engine has done 188 hours.

Thanks in advance.

 

[RichardS]

Strange.

I don't know the SD50 but with my SD20 there's nowhere else for the oil to go other than into the bilge or out of the bottom into the sea.

It's clearly not the drain plug seal as you'd see that so it sounds as if the lower oil / water seals have gone but only actually leak when the shaft is turning so perhaps the original 350ml loss was during the previous voyage?

I assume that your engine oil level is not increasing although I can't really see how the saildrive oil could leak upwards anyway.

It all sounds strange but I can't think of any alternatives.

Richard

 

[duncan99210]

Sounds strange as the usual problem with seals on Saildrives is sea water entry rather than oil loss. Might be worth taking the drain plug out and draining the oil to see if there water it. The only other exit route would be via the input shaft seal: it's possible that there's a considerable quantity of oil now sitting in the housing between the drive and the engine?

 

[BlueChip]

I hadn't used my boat for a couple of months. It remained tied alongside its pontoon finger berth. The week before last, in preparation for a 35 mile journey from marina to hard standing, I checked her over and found that the saildrive had lost oil. It needed about 350ml to restore the level. A week later, just ahead of the trip, I checked again and it needed another 100 ml.

Now in her cradle and with the flex-o-fold prop removed there is no evidence of a leak around the bottom drive shaft or around the drain plug. After this journey, about 4 hours of motoring, I'd estimate another 1-200 ml loss of oil. Hard to be sure but by examining a "dipped finger" of the oil it does not appear emulsified. There's no evidence of a leak inside the hull / engine bay.

Anyone experienced similar? Any ideas of what's going on, more importantly, what's involved in fixing it?

Boat is 2 years old, engine has done 188 hours.

Thanks in advance.

You would know instantly if the leak is inside the boat because gear oil smells horrible, so it can only be that it wasn't topped up correctly in the first place or there is an underwater leak.
The only leak I ever had was when I dropped the o-ring off the filler cap and the top of the saildrive unit got covered in oil.
350 ml oil loss is a huge amount to lose though and 100ml loss without using the engine is almost unbelievable.
When I take the drain plug out, little oil comes out until I remove the filler plug - did you do that?
I bet you didn't and when you do you will immediately see where its leaking from.
I'd put money on a missing o-ring on the drain plug.

 

[Yngmar]

Sounds strange as the usual problem with seals on Saildrives is sea water entry rather than oil loss. Might be worth taking the drain plug out and draining the oil to see if there water it. The only other exit route would be via the input shaft seal: it's possible that there's a considerable quantity of oil now sitting in the housing between the drive and the engine?

+1 to this path of reasoning. The saildrive sits completely below the waterline, so if you had a leak outside the boat, the level would remain the same (or rise if you left the dipstick/filler cap open). There are only two other holes in the thing, a big one for the shaft from the engine, and a small one for the gear lever.

A leak on the gear lever would be fairly obvious, but depending on the engine setup, a leak at the input shaft seal would leak oil into the engine flywheel housing, which is roomy and (normally) filled with air. To check that, you'll have to disconnect the gearbox from the engine. You'll likely find your missing oil.

 

[cmedsailor]

I hadn't used my boat for a couple of months. .

Now this is very bad news to start with!!

 

[Skylark]

Many thanks Duncan and Yngmar, I have the same view and posted to see if anyone else had a similar experience. This is the best section can readily find.

As an approximation, I'd say that the dipstick level puts oil above the input shaft so that seal leaking may be an explanation.

I would be very happy if the problem lay with my saving 10p by not replacing the oil drain washer. I would be suitably embarrassed, quietly keep it to myself, flush it out, refill and forget it. I can't say that I'd be happy with a lower shaft seal failure but at least it would be manageable to fix. "Missing" oil is a nightmare.

The boat is 100 miles from home and was only lifted last Friday. I removed the prop immediately after the hull was jet washed. Maybe after a week or so there may be evidence of an external leak. Frankly, I hope there is.

I'm loathed to drain the oil to look for emulsification as I've asked a Dealer to consider warranty. I may "suck" a small sample out of the fill hole.

(cmedsailor - dreadful season to be honest. we did 70 miles only. 35 from hardstanding to marina in April. 35 miles return to hardstanding in October)

 

[RichardS]

A leak on the gear lever would be fairly obvious, but depending on the engine setup, a leak at the input shaft seal would leak oil into the engine flywheel housing, which is roomy and (normally) filled with air. To check that, you'll have to disconnect the gearbox from the engine. You'll likely find your missing oil.

I've not had my Yanmar out but is that air-filled bell housing a sealed enclosure? I would have thought that, as it is supposed to be empty, it would have a tell-tale hole in the bottom. If it doesn't, and it is sealed, it might fill up with oil until such time as it finds its own level and the oil loss then stops.

Engineering wise, it doesn't sound very clever but maybe your problem will soon fix itself, in a manner of speaking!

Richard

 

[VicS]

I've not had my Yanmar out but is that air-filled bell housing a sealed enclosure? I would have thought that, as it is supposed to be empty, it would have a tell-tale hole in the bottom. If it doesn't, and it is sealed, it might fill up with oil until such time as it finds its own level and the oil loss then stops.

Engineering wise, it doesn't sound very clever but maybe your problem will soon fix itself, in a manner of speaking!

Richard

Isn't it bolted onto the flywheel bellhousing. You'll not want to fill that with oil. That would create some different problems!

 

[RichardS]

Doesn't it bolted onto the flywheel bellhousing. You not want to fill that with oil. That would create some different problems!

..... which is why it's not very clever (with a sad face)!

Richard