Anyone you talk to about Yanmar Saildrives will tell you that the raw water shut offs in the drive leg are problematic (the one exception I know of being another Saint Francis owner I have talked to who seems content with his). There are several problems with the stock shut offs as I see it. First and foremost, they often don't shut off. You might as well just put a straight pipe on there. The screw mechanism is extremely prone to seizure by fouling or minor surface corrosion. Anything getting in the threads (remember this is a raw water shut off so things getting in there is the rule not the exception) will make it nearly impossible to adjust the valve. The tiny wire handle on the top doesn't help matters.

I try to exercise all of my shut offs regularly. When I first tried to turn the Yanmar Saildrive valves about three months after delivery both were seized. We broke one loose but the other was stuck open until removed for service, and this is not the kind of valve you want to take off in the water. Another issue that I noticed after the fact was that when I closed the one valve that was working it wasn't closing all the way. Something had mucked up the threads making it feel closed but there was still quite a bit of gap between the screw and the housing opening. This brings to mind the fact that you can not just look at these shut offs and tell if they are open or closed, an obvious short fall. The stock hose for the raw water is good quality but not wire sided and you can not see through it to tell if water is running or not.

One great thing about Grenada Marine is that they work on a lot of cats and have a lot of experience with many common problems cat owners run across. When I inquired at the mechanical shop they told me that they install standard 90 degree shut offs on Yanmar Saildrives very often for all of the reasons above. A single new Yanmar shut off valve part would cost me more than two quality 90 degree shut offs, new top quality wire sided see through hose and installation! I now have a nice pair of standard shutoffs.