Yanmar - Water out of air intake

[Anyway1]

recently purchased 28' sailing boat with a 1 cyl inboard Yanmar diesel. there were no problems during the pre purchase inspection with the motor, however now after each run the cylinder seems to fill up with sea water. I have to hand crank the motor and collect the water that pushes out of the air intake, after which the motor starts and seems to perform ok only blowing a little bit of white smoke. Needless to say that this is not a good situation - anyone got any ideas where the problem could be?

 

[billcowan]

Sounds like a blown head gasket to me.

Turn off the cooling water sea cock, pull off the top little link hose on the front of the engine and start it from cold. If farting comes out, then thats it. Dont run for more than a few seconds without cooling water though! otherwise you will overheat and exhaust pipe will catch fire.

Also when you have the head off, it sounds as if you should renew the valves.

Actually I have seen these engines secondhand quite cheap.

Any Second opinions?

 

[sailorman]

is it the YSE range ie horizontal cylinder

 

[bendyone]

Check that the exhaust pipe has not moved, there needs to be enough of a downwards pipe going away from the engine to contain the last of the cooling water that has not been pushed out by the gases. If not the water will run back into the engine and cause waterlock.

 

[Evadne]

Check that the anti siphon valve hasn't seized. This would allow the last bit of water from the exhaust to be sucked back into the cylinder head. Also (speaking from experience, sadly,) make sure that the drip tube from the valve doesn't dip into a pool of bilge water, or it will suck this back up into the cylinder.
Either way, if you are getting water into the cylinder,especially salt water, you'll need to get it fixed quick or it will destroy the rings and injector, followed by the valves.

 

[boatmike]

This is probably nearer the truth. Your exhaust is probably siphoning water back when the engine cools. You need an anti-syphon valve in your system. This is simply a device to let air in at the highest point in your exhaust system (usually at the manifold itself or just before or after it on the water intake or outlet from the manifiold so that when the engine stops it does not suck water back up the pipe from the waterlock as the engine cools. In its simplest (and in my opinion best) form it can be a 1/4inch pipe or smaller, lead to a little skin fitting above the waterline. Water will of course normally come out of this when the engine is running but not sufficient to detract from main cooling water flow. when the engine stops air is sucked in through this pipe rather than water from the waterlock silencer. Some have a little one way valve fitted to stop water going out and still allow air in. These often seize up and block the air entry which may well be your problem. Look and see if you have one. If you do, take it apart and remove the valve. You might have a little jet of water out of it that was not there before but lead this over the side and it will never happen again.
I have lost count of the number of diesels I have seen buggered by a sticking valve in an anti-syphon device. A hydraulic lock can bend con rods, hole pistons and smash cylinder heads. Get it fixed before it does!

 

[billcowan]

Mmm. I have a 1GM 7hp yanmar (vertical) - I forgot there was a horizontal type.

I dont have an anti siphon device, but the exhaust pipe is enormously fat and the water trap is well below the top of the engine. I will have to listen to it when it cools and check if there is a gurgling from the trap of air being drawn back.

 

[sailorman]

look on the "Vetus" website they may have a diagramme with dims. relating to water traps, syphon breaks ect
there catologue does have schematic diagrammes

 

[Bilgediver]

This water can either be coming back up the exhaust due to a lack of water trap or one too small for the volume of exhaust system or it could be syphoning from the sea through the inlet.

No matter which and until the problem is sorted you need to stop this as this water will destroy your engine.

I would suggest that until you find the problem you get into the routine of turning the water off every time just before stopping the engine and only turning it on once the engine is running.

I have a friend with twin Yanmars having to do this.

The anti syphon valve in the inlet system should be fitted AFTER the pump between the pump and the engine and the syphon loop should rise from the pump to well above the engine before dropping back to the engine inlet.

There should be a water trap in the exhaust capable of taking the volume of water that accumulates in the exhaust between the engine and hull outlet.

JoHn

 

[Anyway1]

Well first of all thanks to everyone replying to my dilemma. Armed with all the advise from your replies I went down to the boat today to check out a few things. However I was lucky to run into Henry, who is a Canadian an on his trip around the world. Anyway he seemed to now an awful lot about motors and after checking a few things and seeing the water squirting out of the air intake he deceided that the head had to come off. It didn't take long for him to pull the head off- I might add at this point that i learned alot from him about the motor and sailing. The head / gasket and cylinder gave no indication of how the water was getting into the cylinder. So Henry suggested to hand crank the motor to see where the water was coming from, which i did ........ CLOCKWISE. The end of the learning curve is that we pulled apart a perfectly working motor that is turning anti clock wise. (which not a lot of motors do) and doing that it sucked up the residual water in the exhaust and pumped it out of the air intake. Well this lesson will cost me a few hundred dollars, but at least the motor kaputt.
Thanks again

P.S. it is horizontal type motor

 

[corncob]

Anyway, Were is the water line level above or below the engine?

If you have Had water in the bores, it will surely mean that the con-rod has bent. if you have some one remove the cylinder head, check piston protrusion above the cylinder block. It should protrude between 0.015-0.017" if the piston is level or below the lip of the block its means you have a bent rod! This will explain the white/blue smoke (incomplete combustion) Does the engine run lumpy when cold? Have you had any cold starting problems? Do you spend a long time turning the engine over? Sea cock open or shut?