Yanmar SD20 Saildrive Puzzler...I'm stumped

[Zoid]

I'm working on my boat on the hard to put her back in the water in a week or so and ran into this little issue. I shoved a hose up the leading water inlet on my SD20 Saildrive and ran the engine after replacing the impellers on both engines and oil seals on both saildrives. The Port engine worked perfectly and started pumping out water with the exhaust in a few seconds. I let it run for a while and then switched to the starboard side. This time when I ran the engine I got no water coming out the exhaust. I could see it was not pulling water up from the hose that connects to the saildrive. I ensured the seacock was open and everything looked right. Still nothing. So I disconnected the hose that goes from the saildrive to the strainer and put the saildrive end into a bucket full of water, essentially bypassing the saildrive water intake. When I ran the engine this time it worked perfectly, water coming out with the exhaust and was draining from the bucket. This led me to believe that it was not the impeller I had just changed, but maybe a blockage in the water inlet or saildrive. So then reconnected the hose to the saildrive water inlet, but disconnected the other side that goes into the strainer. I blew through the it and air flowed right through the saildrive no problem. I even put the entire saildrive lower unit into a bucket of water and was able to suck up water without much effort. I reconnected the hose back to the strainer just to try again and the same failure, no water in the exhaust! I can see that water is not flowing through the hoses that go from the saildrive to the strainer or from the strainer to the fresh water pump. I've tried to test each part to see where the failure is but am officially stumped. What an I doing wrong? Any ideas? My only other thought at this point is I have some kind of airleak in that hose or somewhere that is pulling in air rather than the water from the intake. Help!?!

[ggray]

Seeing SD20 always gets my attention!

Can you clarify your second sentence? Not sure what/where you mean by shoving up the hose. On the hard, I've run my engines with water only from a jug or, once, from a small tank with a float valve. Never under pressure.

This all does seem odd; maybe you have 2 intermittent problems that complicate the solution.

Are you sure the raw water pump is always turning? Snug belt? Is your kingston cock working properly? I remove mine each haul out and clean and lubricate.

[clownfishsydney]

Not sure what SD20 has to do with this post, as it seems to be related to engine rather than the saildrive (since this is what sucks in the water and expels it).

[ggray]

Well, the water enters through the sail drive, so it could definitely be a factor in the problem.

[arsenelupiga]

i presume you sd 20 similar to sd 50. sd 50 has 2 channels for water in saildrive. maybe one you try to use is blocked and the other one free ?

[Zoid]

To clarify my second sentence, the SD20 has the slits on the side of the lower unit that draw in water, it also has a hole exactly the size of a hose on the very bottom forward of the oil drain plug. Here in Greece I saw several of the mechanics using a hose up this hole to provide fresh water while running the engine on the hard. So I tried it and it worked great on my port side. When you turn on the hose water comes out the slits until you start the engine, leading me to believe they connect at some point in the saildrive. I believe the water pump is working because it works perfectly when pulling from a bucket rather than the saildrive. Not sure what a Kingston cock is, but would love to know in case that could be it. For the SD50, where are the two channels? And do they meet at some point? Thanks everyone!

[MikeTC]

Sounds strange and appears you have tried the obvious. Before returning to the water from the hard I always close the seacock & fill the strainer, only opening the strainer once in the water to ensure an instant flow.

[ggray]

The kingston cock is what Yanmar calls their proprietary shut off valve mounted to the top of the leg, and to which the seawater hose is attached. Those things are expensive, so I always clean with WD40, and lube with Fluid Film or something similar, every haul out. And make sure it opens and closes properly.

Always wondered what that other hole was for. I think I'll stick with my float valve tank, if I can find where I last put it....

[ggray]

Now that I've read your second post, the first makes more sense.

Sounds like there surely is an issue inside the lower leg. Not knowing the internal relationship between the forward hole and the slotted holes, it's hard for me to critique that.

I'm not sure if you have tried running the motor with that water bucket enclosing and submerging the sail drive (or just sucked on the hose in that position), but that is more like the environment that your engine will be operating in, so I'd try doing that.

Good luck!

[yachttie]

Have you thought that a plastic bag or similar might have been drawn up the intake (the round hole you describe)?
I had that happen on one of my SD20s. it did not stop water flowing to the pump, as water can presumably also be drawn through the side grills.
I used an old wire coat hanger & straightened it out, leaving a small (15mm) bend at the end. I then poked it up & twisted at the same time. Keep pulling it back down to clear any obstruction.
Good Luck⛵️

[PaulMarion]

I've had that hole completely blocked with gunk, shell, worm etc, to the stage it didn't even look as though their was one! Start by poking with heavy fencing wire, or an old coat hanger, and continue to open it until you get through whatever is blocking it. I also suggest you use either a long thin screwdriver and fencing wire to clean through and up into the leg via the side slits, as these also get worm, shell and often crabs residing there. As we live in Queensland and visit many reef areas, it's imperative to keep these areas clean. I've found at times when water flow seems unequal from either motor, ( We have a Lavezzi 40 cat, twin SD20's) I sometimes pop over the side with the hooker and give those areas a poke to make sure they're clean. Another prime area is at the sea cock at the base of the saildrive. I've had two occasions where water flow was restricted and found even though the seacock was opening, closing freely, the water was not flowing freely enough when the hose was removed from the cock. WARNING!! Do not remove the hose unless you know for sure the cock is closing..AND also you have both new hose available and a new clamp, if either is damaged on removal!! After removing the hose, with the valve closed and having a container under or a towel around the saildrive base, open the cock, and using a length of heavy fencing wire poke in and around as far as you can. This will always dislodge any growth and free up anything clogging or restricting the pipe on the inside of the seacock. Yes, it's always possible there is a hose sucking air, however a give away to the problem is the water strainer bowl being low and showing bubbles in it. Definitely check these areas on haulout, as you will be surprised how much crap comes out! Happy Sailing, Regards Paul.

[millhouse_44]

You're getting an air lock in the system. Hook it up again, start the engine and if no water is coming out loosen the demand side hose on your water pump and crack it off until water flows out then close it again. This will jump start the flow and solve the problem. It's not blocked based on what you've described.

[Zoid]

Interesting update for those that are interested. I did my best to clean any blockages, but didn't find anything of significance. I submerged the entire lower saildrive below the hull (covering all water inlets) in a large bucket filled with fresh water and a running hose in it. When I ran the engine the same result, no exhaust water. I climbed into the engine compartment and could see large air pockets in the lines that were not moving. I grabbed one line, the line from the saildrive seacock to the strainer, and manually manipulated the line to coerce the air pocket up to the strainer. Once I was able to do that everything started working perfectly. So it appears it is caused by an air lock. After running it for about 2 minutes the hose slipped out of the bucket so I stopped the engine. I put the hose back in and started again, and guess what? Same air pocket issue. So I manually manipulated it to the strainer again and it started working again. So I guess I'm glad to know what it is, but worried that this will happen every time. Hard to know what she will do in the water until I launch her. Thoughts?

[millhouse_44]

Once the air is out it will work fine on the water. Cheers.

[aluijten]

Originally Posted by Zoid

Interesting update for those that are interested. I did my best to clean any blockages, but didn't find anything of significance. I submerged the entire lower saildrive below the hull (covering all water inlets) in a large bucket filled with fresh water and a running hose in it. When I ran the engine the same result, no exhaust water. I climbed into the engine compartment and could see large air pockets in the lines that were not moving. I grabbed one line, the line from the saildrive seacock to the strainer, and manually manipulated the line to coerce the air pocket up to the strainer. Once I was able to do that everything started working perfectly. So it appears it is caused by an air lock. After running it for about 2 minutes the hose slipped out of the bucket so I stopped the engine. I put the hose back in and started again, and guess what? Same air pocket issue. So I manually manipulated it to the strainer again and it started working again. So I guess I'm glad to know what it is, but worried that this will happen every time. Hard to know what she will do in the water until I launch her. Thoughts?

You may have an worn out impeller pump. Once the pump wears out you get leakage along the sides of the impeller. This is especially noticeable when the pump starts empty. It will no longer create enough vacuum to prime the waterflow. You can test this (if possible) by reversing the impeller cover to create a new surface for the impeller. Or buy a new cover.