Re: Volvo QS BP1200 bow thruster replacement
Posted: June 23rd, 2021, 8:56 pm
The QLs have an oil reservoir so any pressure would send oil back up the feed line. It's not an appreciable amount though but when that happens, it either goes up the line or out through a leak. Depending on the leak, when going up the line, the volume it displaces has to be replaced by something else...water if it can. In a sense, at that spot, it'll create a vacuum and bring water in. For that reason, some sterndrives require both a pressure test and a vacuum test to ensure the seals are working both ways. The difference with a lower unit is way higher rpm, pressure, and temperature, not nearly the same conditions as a thruster leg operation.
I started thinking about all the sources of how petroleum products make their way into the waterways on boats. Taking measures to eliminate as much of that as possible is a good thing whether at the manufacturing or ownership level. Techs can make a huge difference here too. Don't know how many times I see techs greasing all the points on a sterndrive and not even bother to clean the excess grease off the grease nipple. Marinas can play a huge roll too. All too often I see marinas launching boats where the trim tab actuators are clearly leaking, that should be an automatic no launch until it's fixed. It may seem like a small amount but add that up for all the sterndrives, trim tab actuators, etc. out there...it all adds up. Sterndrives are the worst, there's so much grease in the water with them. Heaven forbid you have a bad enough impact to break the lower unit and spill it's entire contents of gear lube. You know, they push marinas to use vegetable based oils and greases for their equipment working around the water but there's nothing said about what gets used in vessel hardware actually running and sitting in water all the time. Having said that, I think it's just a matter of time before that changes.
I started thinking about all the sources of how petroleum products make their way into the waterways on boats. Taking measures to eliminate as much of that as possible is a good thing whether at the manufacturing or ownership level. Techs can make a huge difference here too. Don't know how many times I see techs greasing all the points on a sterndrive and not even bother to clean the excess grease off the grease nipple. Marinas can play a huge roll too. All too often I see marinas launching boats where the trim tab actuators are clearly leaking, that should be an automatic no launch until it's fixed. It may seem like a small amount but add that up for all the sterndrives, trim tab actuators, etc. out there...it all adds up. Sterndrives are the worst, there's so much grease in the water with them. Heaven forbid you have a bad enough impact to break the lower unit and spill it's entire contents of gear lube. You know, they push marinas to use vegetable based oils and greases for their equipment working around the water but there's nothing said about what gets used in vessel hardware actually running and sitting in water all the time. Having said that, I think it's just a matter of time before that changes.