Header Tank To Eliminate Saildrive Salt Water Intrusion

[pmar]

Hello, today i found out that oil in my 130S Volvo penta saildrive is looking like milk, probably I've made already around 30h on it which is scary but everything seems to work well, I immidetly pumped out the oil 3 times, and filled new, to get rid of the water, I am planing to do so at least 2 more times until oil will be clear. It will take some time until i will be able to take boat out of the water to replace seals..

I am planning to mount external oil tank hopefullty to prevent getting more water into oil until i fix the problem. I have around 60cm of space above waterline to do so, which should be enough to pressurize system with olny mass of oil. Neverthless idea to me is new, I just found this topic when i've been looking for solution to mitigate the issue, so i would humbly ask for Your support.

Could You tell me if i understood the idea correcly:
Im should mount some over flow tank like this one (ideally with vent): https://www.aircraftspruce.com/catal.../reservoir.php around 60cm (20 inches) above waterline. Then connect it with some oil hose to cap fitted in place of oil dipstick (like this https://www.juddracing.com/products/...-breather.html) and overflow whole system with oil (of course i will leave like half of installed tank empty to give oil possibility to expand) and that's it?
If I am correct, could You tell me how big the overflow tank should be?

Thanks, pmar

[team karst]

I use this one for overflow tank:

https://www.amazon.com/Dorman-603-00...s%2C107&sr=8-1

as high as you can get it.

[Tupaia]

Originally Posted by pmar

Hello, today i found out that oil in my 130S Volvo penta saildrive is looking like milk, probably I've made already around 30h on it which is scary but everything seems to work well, I immidetly pumped out the oil 3 times, and filled new, to get rid of the water, I am planing to do so at least 2 more times until oil will be clear. It will take some time until i will be able to take boat out of the water to replace seals..

I am planning to mount external oil tank hopefullty to prevent getting more water into oil until i fix the problem. I have around 60cm of space above waterline to do so, which should be enough to pressurize system with olny mass of oil. Neverthless idea to me is new, I just found this topic when i've been looking for solution to mitigate the issue, so i would humbly ask for Your support.

Could You tell me if i understood the idea correcly:
Im should mount some over flow tank like this one (ideally with vent): https://www.aircraftspruce.com/catal.../reservoir.php around 60cm (20 inches) above waterline. Then connect it with some oil hose to cap fitted in place of oil dipstick (like this https://www.juddracing.com/products/...-breather.html) and overflow whole system with oil (of course i will leave like half of installed tank empty to give oil possibility to expand) and that's it?
If I am correct, could You tell me how big the overflow tank should be?

Thanks, pmar

It is more likely that the seal has failed or was not installed correctly, just replace the seals. On a monohull the SD is usually so deep in the water that the differential pressure between the level of the oil and water are such that a header tank will not help.

[HeywoodJ]

Originally Posted by pmar

Could You tell me if i understood the idea correcly:
Im should mount some over flow tank like this one (ideally with vent): https://www.aircraftspruce.com/catal.../reservoir.php around 60cm (20 inches) above waterline. Then connect it with some oil hose to cap fitted in place of oil dipstick (like this https://www.juddracing.com/products/...-breather.html) and overflow whole system with oil (of course i will leave like half of installed tank empty to give oil possibility to expand) and that's it?
If I am correct, could You tell me how big the overflow tank should be?

Thanks, pmar

You understand correctly. The size of the tank is generally 20-40% of the oil capacity of the saildrive. If you fill it halfway that means it will contain 10-20% of the capacity of the saildrive. If your leak is significant you might want a larger tank just to keep from having to fill it.

Originally Posted by Tupaia

It is more likely that the seal has failed or was not installed correctly, just replace the seals. On a monohull the SD is usually so deep in the water that the differential pressure between the level of the oil and water are such that a header tank will not help.

Header tank will do the same regardless of how deep the SD is in the hull and water. The key is understanding how they work. 90W gear oil has a density about 85-90% that of seawater. That means that to match the seawater pressure you need to know the distance (depth) from waterline to SD seal and the oil level in the tank should be about 15% of that measurement above the waterline. If you want slight positive pressure you put it a bit higher. Sounds like pmars' plan is just about right.

[ggray]

Originally Posted by pmar

Could You tell me if i understood the idea correcly:
Im mounting some over flow tank like this one (ideally with vent): https://www.aircraftspruce.com/catal.../reservoir.php around 60cm (20 inches) above waterline. then connect it with some oil hose to cap fitted in place of oil dipstick (like this https://www.juddracing.com/products/...-breather.html) and overflow whole system with oil (of course i will leave like half of installed tank empty to give oil possibility to expand) and that's it?
If I am correct, could You tell me how big the overflow tank should be?

Thanks, pmar

That is a very large tank! I had ordered a tank from Mercruiser, in spite of the high price, as I had a water leakage problem with one of my SD20s and was in no position to haul out. When it didn't arrive in time, I scrambled and found parts in my shop to make one.

A 5.25 oz Lucas Fuel Injector Cleaner bottle and a 1/4 NPT to 1/4 hose barb fitting that I glued in the neck. Invert and cut the bottom off; the outer part of a gallon pink antifreeze jug cap fits just fine as a cap. This is a good size for the job and doesn't get in the way.

I just pressed a 1/4" SS tube into the cap after I drilled out where the dip stick was. One thing you didn't mention is to install a pinch valve on the tube between the bottle and the cap should you ever need to remove the cap with a full bottle, not that I ever have.

I changed the little oil I could remove 9 times before I was happy

[pmar]

As soon as leak was fixed I've finished my instalation, pictures below, wondering if not to add more oil to tank (around 400-500ml currently). I've used Judd plug advertised in thread (crazy expensive as tax+duty from UK were added) and Dorman tank(only modification i've made was to increased venting hole size from 0,5 to 2mm). My little concern is that i used 8mm fuel hose, and plug had 6mm head so had to tighten clamp a little, hopefully it will not start to leak.
https://ibb.co/zJt4NMX
https://ibb.co/T2HLqDr
https://ibb.co/kc7dpqM

[team karst]

Looks ok. I use a clear hose. Within a foot of the xmission attach i have seen water vapor condense inside the hose during a hard run. Nice to see that since it since it is an indication of wet oil; These run at around 170 deg F.

[pmar]

Like normal clear PVC tube? I see advantage of seeing through hose...

[team karst]

Originally Posted by pmar

Like normal clear PVC tube? I see advantage of seeing through hose...

Yes. It will harden over time tho. So it’s best used while the water threat is ongoing.

[ggray]

Yes, the vinyl tube does harden, so I replace the tube at haulout, usually every other year, when I also change the oil.

I think it is helpful seeing the oil (and initially air bubbles) in the tube.

I've been doing this for 20 years now.