Engine flushing

[Stevan47]

Hi everyone: I need some advice, please. My 2009/2010 R21-EC has the Yanmar 3YM30 engine. As you may know there is a flushing connection on the stbd side of the engine, just f'rd of the strainer. When connected to a garden hose this flushes the sea water inlet back out through the hull-mounted inlet grate and also forces some water down through the Johnson pump impeller and on through the cooling system (albeit, not much gets past the impeller while stationary, so I am doubtful as to how much fresh water actually passes through the heat exchanger).

Since acquiring the boat, I have always flushed the system this way, but have never actually run the engine with the hose connected under water pressure. I have been reluctant to start the engine while on the trailer,out of the water, as I believe there would be excessive vibration which could damage the engine and /or hull, despite the resilient mountings. It seems to me that without running the engine and thereby forcing cooling water through the whole system, it is not getting flushed completely. Just my thoughts.

Has anybody ever run their engine out of the water, with cooling water hose attached? Is this not recommended? I would be happy to take advice/suggestions on this. Regards, Stevan

 

[stwendl]

They make this gadget which looks like a plunger to free your sink drain. It has a water hose connection and an extending stick. When the boat is on the trailer you jam the cup against the hull over the water intake and then extend the stick against the ground. Turn on the water, not too much after the engine is started and this will flush your engine.

My Volvo service guy used that during service. You can buy this at west marine or any motor boat supply store. I was told if you put too much pressure on the inlet it can cause water to enter the cylinders. There are some stories on this site where owners got their boat towed while the raw water intake was not closed and consequently got water locked.

So just take this as input to consider next time you select your water pressure

 

[Stevan47]

Hi Stwendl: thanks for the advice. I can certainly visualise the device and also understand the risks of excessive water pressure, but if I cannot acquire one of these devices, is there any reason why I can't just shut off the inlet cock inside the hull, and utilise the flushing connection, next to the strainer, with a garden hose at normal water pressure? Is that likely to induce water into the cylinder/s? Your thoughts? Stevan

 

[lone ranger]

I shut the seacock ,connect the garden hose to the adapter and run the engine to flush.i did this in and out of water.just remember to open the seacock before again before heading out.

 

[knotflying]

I would be reluctant with a direct connection with a hose. I open my sea strainer, close the sea cock and place a hose on the strainer. Inten start the engine and just make sure the hose does not fall out of the strainer. With a direct connection I am afraid of forcing too much water through and perhaps causing water to back down the exhaust manifold. Maybe I am being too cautious.

 

[Stevan47]

Hi guys: thanks for being so prompt with your suggestions. It is reassuring. I just received a reply from Andrew Custis, which I have attached below. It mirrors what you are telling me too.

By Andrew Custis: "That fresh water flush fitting is designed to flush the engine while out of the water. Get it running first as you've been doing and then close the seacock. Before you shut it off, open it back up so you don't pressurize the system with water"

On this topic, I did some research on the internet and went to the 'Moeller Marine' website. They are in your part of the world. They have a device called the 'Moeller Inboard Flusher' which comes with an extendable alloy pole, on the end is a rubber cup-like device, including a hose connection/fitting, which fits over the seawater inlet grate. 'Stwendl' mentioned this in his email and this prompted me to look further into it.

Moeller also have a second similar design device, without the extendable pole, and this has a stainless steel plate which hooks into the grate, inside the rubber cup head. You then screw down on a star nut, which is threaded on the short shaft. This then clamps firmly to the hull. You just attach the hose and away you go. It is called the 'Moeller Pro Motor Inboard Flusher'. I have just ordered one via Amazon.com and it should be here in a week or so. I think this shorter, screw down version is a better design and is not dependant on bracing the pole on the ground. I will let you know how it goes when I give it a try. In the meantime, thanks to you all for your advice and suggestions. Kindest regards, Stevan

 

[daylekuhn]

I installed T connections with hose,female hose connectors and ball valve, between the strainers and the impellors on both the engine and generator. I use the ball valve to open and close the hose down to the "T". It hooks up to a standard garden hose. With boat out of water, I attach the hose, turn on the water, make sure the ball valve is closed so no water can enter to impellor intake hose thru "T", and proceed to flush out the engine as follows, first make sure to open strainer thru hull, this allows water to flow out thru hull putting very little pressure to impellor. next open ball valve allowing water to flow to engine and also back out the thru hull. Next start engine at this time you will note water stops flowing out thru hull and enters engine (path of least resistance with impellor turning), It only takes about 5 seconds to get from ball valve to start engine so very little water if any can enter thru impellor into engine to cause any problems. On the generator I start it first, as it can take more time to get going and then I go back and turn ball valve on so water can flow thru "T"to gen. so the generator is running dry for about 5 seconds. I have done this dozens of times with no problems. It also allows me to winterize the engine, gen. and ac units very easy. It worked so well I installed one on A/C intake, I use a 5 gal. bucket filled with antifreeze with a hose and valve attach on bottom of it. I hook it up to ball valve and use the same procedure.

 

[stwendl]

The point of the rubber cups is that there is a pressure release of the pressure gets to high to flood the engine. This can. E accommodated with running the engine before water pressure is applied to the inlet and after water is shut off. Some can probably come up with a fancy pressure regulator for this too that simulates the pressure at the inlet while submerged🙂

 

[LAKERtoo]

.. I take a short piece of hose (4'-5') and screw onto the fitting, with the intake end into a large bucket / tub of water that in turn has a garden hose keeping it topped up .. have a second person monitoring this full tub .. close the seacock and start as normal .. same process for installing winter anti-freeze .. no chance of over pressurizing .. Rob

 

[SGIDAVE]

Hello Stevan,

I either do the short length of hose in a bucket being filled by the garden hose like Rob (Lakertoo) OR I will used the hose directly connected to the fitting you describe.

When using the direct connect method you must be careful not to force water into the engine as others have stated. I accomplish this by using a 'shut-off' at the end of the hose like this

Then I start the engine and walk two steps back to the engine to open the hose-end shutoff so that it is now on. With this technique the hose pressure is never 'on' when the engine is off. There is an emergency shut off on the side of the Yanmar 3YM which I use to end the process. The hose end shut off is turned off then the red emergency stop is depressed to stop the engine.

I believe the risk here is using hose pressure whilst the engine is OFF. Once running, the impeller is allowing passage of water through the heat exchanger where it ultimately is expelled in the exhaust and the running engine with pressurized cylinders prohibits retrograde entry of water through the valve train.

So either the direct connect method is fine if you are careful to avoid pressurizing the engine before starting it OR letting the engine suck water out of a bucket.

The 3YM Yanmar in the 21EC will "winterize" with just under 1 gallon of antifreeze...I just stick a short length of hose directly into the gallon jug, start the engine, then shut the engine down just as the gallon empties (using the emergency shut off on the side of the engine. The one gallon quantity perfectly fills the heat exchanger, coolant hoses, and water lift muffler. Easy Peasy!

 

[Stevan47]

Thanks Dave: that is brilliant. Just what I was thinking too. I will get one of those shut-off cocks to add to the hose - simple but effective. Never thought of it before. As for winterizing the engine - never have to worry about that down here.
Even in our winter, like now, it never gets down past about three to four degrees Celsius at night, and rarely below six to ten degrees in the day. It is usually boating weather all year round, except for some really stormy weeks. Incidentally,do you get much vibration when running the engine out of the water and on a trailer? Stevan