I have a Volvo saildrive and I'm wondering if anyone has changed the water intake from a skin fitting in the hull rather than through the leg. The leg becomes quickly clogged with oysters and other little growing creatures and is very hard to keep clear when the boat is in the water. We live in the tropics in Australia and the water temperature can be as high as 30 degrees celcius encouraging marine growth. Our Volvo mechanic says it would be okay to do it, but Volvo say no because the water needs to go through the pipe in the leg to cool it. However, if the leg is in the water anyway, what's the diff?
Cooling water on Saildrive
- Thread starter Bing
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C'mon everybody. Surely somebody has an opinion on this. We are having the boat hauled out in a couple of weeks and would like to know one way or the other.
I am not knowledgable on the internals of a sail drive but have some experence with OB's and diesel wet exhausts.
What is the purpose of the water in the leg? Is the water there for the exhaust to make it a wet exhaust? With your modified water inlet the wet exhaust would still exist. There would be no change to the engine cooling or exhaust cooling.
Is the water used to cool something in its entry into the motor? Something that has nothing to do with the exhaust? I can't think of anything that requires incoming water for cooling.
Is it possible that Volvo mis-understood your question? Put this question to a qualified Volvo mechanic. I think you have a good idea.
Ray
What is the purpose of the water in the leg? Is the water there for the exhaust to make it a wet exhaust? With your modified water inlet the wet exhaust would still exist. There would be no change to the engine cooling or exhaust cooling.
Is the water used to cool something in its entry into the motor? Something that has nothing to do with the exhaust? I can't think of anything that requires incoming water for cooling.
Is it possible that Volvo mis-understood your question? Put this question to a qualified Volvo mechanic. I think you have a good idea.
Ray
Thanks Ray. That confirms my thinking. The salt water is pumped up through a heat exchanger and then into the wet exhaust. It doesn't go anywhere near the gearbox of the saildrive, just 18 inches into the leg. So it shouldn't matter where the water comes from. I have asked the authorised Volvo mechanic, and he said it would be okay. It's just Volvo Australia who gave me a very strange answer about cooling the leg.
Bing, I have a 2005 Bav 32 with a Volvo 130S saildrive which should be similar if not identical to yours. I believe they want the water flow to cool the transmission. I was told the best way clear the leg is with a 3 foot length of 3/8 inch threaded rod. There is a hole at the bottom of the leg near the oil drain plug. Use the rod to ream the inside. Make sure you buy a cheap zinc rod, not stainless steel, as zinc is kinder on aluminum. I found my rod at Home Depot. The 3 foot length is long enough to reach the through hull and short enough to insert when you're on the hard.
Thanks, cbsura. I've been using plastic conduit to clean the leg, but will look into your suggestion. When you say transmission, do you mean the drive shaft, or the gearbox?
I believe I would try it. Cooling an underwater apparatus with water seems, well, you get the idea. I have more hands-on with OMC saildrives, and the very idea of am impeller in the drive, underwater, which necessitates hauling the boat, and pulling the engine to change a twenty dollar impeller has GOT to be in the top ten dumbest plans ever inflicted on a sailboater. So, yeah, I would have to try it. If you do not permanently disable the intake that resides there now, you can always just shut the valve on the new thru-hull, or just use it for something else.
I would be very interested in whether you made it work. Sorry to put the testing and engineering on you, but if it worked, that would be huge..
I would be very interested in whether you made it work. Sorry to put the testing and engineering on you, but if it worked, that would be huge..
If the Volvo distributor said water is required to "cool the leg" I don't think it would be wise to ignore their advice without a well researched technical justification. The power train in the leg is bathed in oil all the way down to the shaft seal by the prop. Perhaps the water flow in the leg serves to cool the oil in the internal jacket? This is just speculation, of course, but I can't imagine why Volvo would engineer the more expensive water path through the leg if it didn't serve a purpose.
Also, to Chris P's question, there is no impeller in the Volvo saildrive. The impeller is in the engine's water pump where it belongs -- in a serviceable location.
Also, to Chris P's question, there is no impeller in the Volvo saildrive. The impeller is in the engine's water pump where it belongs -- in a serviceable location.
I have a an older Volvo diesel with a 110s saildrive that has cooling water moved off the 110s to a dedicated through hull. I believe the original design had all cooling water for the diesel going through the saildrive. A new water pump was installed at the through hull as well. No impellers that I saw when changing seals on the saildrive but mine is older. This motor and saildrive are from the early 80s and does fine in 70-75*F water but hardly tropical.
Not sure if it helps but thought I'd offer this as more info.
Good luck!
SC
Not sure if it helps but thought I'd offer this as more info.
Good luck!
SC
Bing,
I can't adequately speak on the technical aspects of the leg cooling, maybe PM Never Monday or Mainsail for that, but have you tried regularly back flushing the drive with fresh water under water main pressure? Just disconnect your intake at the strainer and attach a water hose to your intake hose. Then open the thru hull and turn on the water. Run full blast for several minutes. If you do this often enough, it may prove helpful. (Hopefully)
Tom
I can't adequately speak on the technical aspects of the leg cooling, maybe PM Never Monday or Mainsail for that, but have you tried regularly back flushing the drive with fresh water under water main pressure? Just disconnect your intake at the strainer and attach a water hose to your intake hose. Then open the thru hull and turn on the water. Run full blast for several minutes. If you do this often enough, it may prove helpful. (Hopefully)
Tom
I have a 110S sail drive. I moved the engine inlet to a thru hull. No issues. Its just a pipe up the drive and provides no cooling properties to the drive. I now get a Lot more water out the exhaust.
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