This would help, but it might also result in oil squirting out the hole. I see my oil level in the tank go up quite a bit when it gets hot. Also, comtaminants could get in.
But the oil level in the SD20 is much lower than the waterline. Oil is lighter than water. So if you don't raise the oil level a good bit higher than the waterline, the water pressure on the seal will be higher than the oil pressure inside. If the seal
leaks, you will get water inside.
But why stop here ? It is very easy to make a tank. I had ordered 2 from Mercruiser (kind of expensive, but the only smallish ones I could find), but when they weren't shipped as promised, in my desperation I looked around my shop for an alternative. I found a small, tall and skinny plastic bottle (Lucas gas additive, for
cleaning injectors, I think). I cleaned it, cut the bottom off and glued into the bottle mouth a plastic fitting with a 1/4 iThis would help, but it might also result in oil squirting out the hole. I see my oil level in the tank go up quite a bit when it gets hot. Also, comtaminants could get in.
But the oil level in the SD20 is much lower than the waterline. Oil is lighter than water. So if you don't raise the oil level a good bit higher than the waterline, the water pressure on the seal will be higher than the oil pressure inside. If the seal
leaks, you will get water inside.
But why stop here ? It is very easy to make a tank. I had ordered 2 from Mercruiser (kind of expensive, but the only smallish ones I could find), but when they weren't shipped as promised, in my desperation I looked around my shop for an alternative. I found a small, tall and skinny plastic bottle nch barb for the tubing. The tubing connects to the 1/4 inch ss tube inserted into the SD20 fill cap. I threaded one of those plastic pinch "valves" on the tube near the cap so the cap could be removed when the tank is full. Last, I made a tank cap out of the outer portion of the "child proof" cap on a 1 gallon
marine anti freeze jug. Mounted the tank with wire ties and wire tie pads.
If these products aren't available in
Australia, you should be able to find something similar.
I should add that this probably is not
Yanmar approved. While I adjusted the length of the ss tube in the fill cap to be at the correct "full" level, I would not be surprised if the air space hasn't disappeared and now full of oil. I can't see where this could cause problems though. I'm guessing that the air space above the "full" level is to absorb the expansion of the oil, because as built, the
saildrive is not vented. My expansion
tanks now take care of this. I've had these in use for 5 years now.