Air lock? - Problem solved

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   Hi chaps,
As usual I serviced the engine whilst the boat was on the hard and I tend to run the engine with a hose in the strainer so that the oil becomes warm and easier to remove from the sump with a vacuum pump.

Once the filters are all changed and a new impeller fitted, I run the engine again to check for leaks. Again hose supplying water to the strainer, which also sends excess water down the sail drive.

So, when the boat went back in the water and I start the engine, no water comes out of the exhaust.  This is not the first time I've services the engine this way so cannot understand why I'm not seeing water out of the exhaust.  Has an air lock been created at the siphon or anywhere else?

I've tipped water down the strainer to 'fill' the pipe to the impeller in case this needed to be primed and create da vacuum.  I don't remember having this issue in the past, anyone got any ideas?

Edited by JonB - 08 April 2023 at 19:28

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JonB Members Profile Send Private Message Find Members Posts Add to Buddy List Rear Admiral Joined: 21 September 2010 Location: Cowes Status: Offline Points: 504	Post Options Post Reply Quote JonB Report Post Thanks(0) Quote Reply Topic: Air lock? - Problem solved Posted: 01 April 2023 at 18:46
	Hi chaps, As usual I serviced the engine whilst the boat was on the hard and I tend to run the engine with a hose in the strainer so that the oil becomes warm and easier to remove from the sump with a vacuum pump. Once the filters are all changed and a new impeller fitted, I run the engine again to check for leaks. Again hose supplying water to the strainer, which also sends excess water down the sail drive. So, when the boat went back in the water and I start the engine, no water comes out of the exhaust. This is not the first time I've services the engine this way so cannot understand why I'm not seeing water out of the exhaust. Has an air lock been created at the siphon or anywhere else? I've tipped water down the strainer to 'fill' the pipe to the impeller in case this needed to be primed and create da vacuum. I don't remember having this issue in the past, anyone got any ideas? Edited by JonB - 08 April 2023 at 19:28
	Jon B 470e http://www.norse-king.blogspot.co.uk

Jojo Members Profile Send Private Message Find Members Posts Add to Buddy List Captain Joined: 03 August 2022 Location: liljeholmen swe Status: Offline Points: 166	Post Options Post Reply Quote Jojo Report Post Thanks(0) Quote Reply Posted: 01 April 2023 at 19:08
	hallo Sometimes it takes longer for the water to get to the impeller I have always put in a little extra rev when starting first time in the water after a long winter That helps the water to fill the entire system a little faster Remember your seawaterfilter is above waterlevel and that you must overcome Regards jonas
	3 Cabin, Hanse 342, Deep draft, Tiller version.

Wayne's World Members Profile Send Private Message Find Members Posts Add to Buddy List Admiral Joined: 18 July 2012 Location: Cruising Status: Online Points: 1434	Post Options Post Reply Quote Wayne's World Report Post Thanks(0) Quote Reply Posted: 01 April 2023 at 19:09
	Jon B, Could the sea water strainer be clogged with seaweed etc? Maybe the new impeller failed?
	Wayne W Cruising, currently in the Pacific until the end of 2026.

Martin&Rene Members Profile Send Private Message Find Members Posts Add to Buddy List Vice Admiral Joined: 06 December 2009 Location: United Kingdom Status: Offline Points: 967	Post Options Post Reply Quote Martin&Rene Report Post Thanks(0) Quote Reply Posted: 01 April 2023 at 20:10
	I have a 341 with a Yanmar 2GM20F engine and since it has a an E or YEU designation (meaning, as I understand it), it was finished in Europe with a Johnson pump. Basically, my pump never self primes. So this is my procedure. Firstly, forget the lubricant that comes with the impellor, and coat it all over with a thick layer of vaseline. Drop yacht in water, open saildrive seacock to partially fill up inlet pipe and then shut it. Remove pipe that runs from the pump to the heat exchanger at the heat exchanger end. Pour water into sea water strainer and at some point water may come out of the pipe to the heat exchanger, so then at that point re-attach pipe to heat exchanger. This should fill the pump with water and may help clear any airlocks. Fill up strainer to absolute top level and refit top. Open saildrive seawater inlet valve. Start engine with throttle set at at least half revs. My local engineering shop only supplies Jabasco impellers, and I think it was one of those that repeatedly lost prime when the engine was sat at idle whilst we were in locks on the Crinan Canal. I have just had to fit one of those this year, but when I next come across a place supplying Johnson/Yanmar impellers, I will buy a couple. I change impellors every year. though I can see the price has more than doubled in the 12 years that I have had the yacht. I am surprised you run the engine with the yacht on the hard, as that is specifically banned at Largs Marina. I always do the oil change at the end of the year, before pulling the yacht out of the water, so it has clean oil in it over winter.
	Martin&Rene Hanse 341 Dipper Wheel steering, 3 cabin layout, normally based in Scotland

JonB Members Profile Send Private Message Find Members Posts Add to Buddy List Rear Admiral Joined: 21 September 2010 Location: Cowes Status: Offline Points: 504	Post Options Post Reply Quote JonB Report Post Thanks(0) Quote Reply Posted: 02 April 2023 at 11:42
	NK was in Inverkip originally but we brought him down 11 years ago. I removed the impeller when back in the marina just to check that the fins were facing the correct way, nothing was damaged and seemed fine, so put it back. Sea strainer is cleared as part of my 'putting him to bed' process as the river does have a lot of weed and I'd rather remove it, whilst 'fresh' than try to dig out a black mess next time. Even the run from the marina down to his berth in the river didn't 'lift' fill the system. I fitted oil pressure and water temp gauges a while back, a spin off from my motor rallying days in my youth and my son's hobby now. So I could keep an eye on engine temps. My 470 has a 4JHE has both fresh and sea water coolants, When draining the fresh, yes, I've removed the hose by the clarifier to prevent an air lock there. I don't shut off the sea cock to the sail drive, but that might be the way to go. Shut it and fill the system from the siphon back through, the top of which is higher than the strainer, so that should fill and also the pipe to the sea cock. Start the engine and hopefully create a vacuum and open the sea cock drawing water as normal. I'll give that a go. Thanks for the responses, as I said never had an issue before.
	Jon B 470e http://www.norse-king.blogspot.co.uk

Arcadia Members Profile Send Private Message Find Members Posts Add to Buddy List Admiral Joined: 27 November 2017 Location: Sag Harbor, USA Status: Offline Points: 1112	Post Options Post Reply Quote Arcadia Report Post Thanks(0) Quote Reply Posted: 02 April 2023 at 13:57
	This may sound obvious, but check for small air leaks in the suction side of the system. Even a poorly sealed strainer lid can suck air enough to prevent a proper vacuum to draw the water up to the pump. These small leaks may not leak water at all since there is no pressure when the pump is off and only a vacuum when running.
	Leon / ARCADIA 2018 Hanse 588 Sag Harbor, NY

Stamford Members Profile Send Private Message Find Members Posts Add to Buddy List Sub Lieutenant Joined: 18 October 2017 Status: Offline Points: 3	Post Options Post Reply Quote Stamford Report Post Thanks(0) Quote Reply Posted: 02 April 2023 at 14:05
	i do similar to you & my yard also prohibits running ashore. I'm curious how do you winterise your engine seawater cooling ? In the absence of the usual " suck from a bucket of antifreeze & wait until it spits out of the exhaust" method......

JonB Members Profile Send Private Message Find Members Posts Add to Buddy List Rear Admiral Joined: 21 September 2010 Location: Cowes Status: Offline Points: 504	Post Options Post Reply Quote JonB Report Post Thanks(0) Quote Reply Posted: 02 April 2023 at 14:08
	Too true, I fitted a deck wash pump which has a valve under the master cabin sink so I can switch between fresh or sea water supply, one for the deck/anchor and the other for the pulleys removing the salts. Having made the T connection to the fresh water supply nothing came out, when I tested it. All looked ok and I opted to go home and think about it, rather than get frustrated. I checked all the fittings and tightened any I thought might be loose and tried again. Hay presto result. On one occasion I felt a suction on the strainer lid as I removed it. So I think as you say it's worth just checking all the fittings and wiping the O ring to make sure its making a air tight seal. It is usually the obvious that you miss.
	Jon B 470e http://www.norse-king.blogspot.co.uk

JonB Members Profile Send Private Message Find Members Posts Add to Buddy List Rear Admiral Joined: 21 September 2010 Location: Cowes Status: Offline Points: 504	Post Options Post Reply Quote JonB Report Post Thanks(0) Quote Reply Posted: 02 April 2023 at 14:27
	The Yanmar 4JH4 has twin cooling systems, fresh and sea. The fresh is sealed and has anti-freeze and is used to heat the clarifier, (hot water tank), the sea water, as we know, is drawn up from the sail drive, through the strainer down to the impeller up and over the siphon before entering the heat exchanger and out through the exhaust. The freshwater side has antifreeze in it and fortunately here on the Isle of Wight the lowest temperature this January was +2C, I have a max/min thermometer in the bilge by the fresh water tanks. Having fitted the deck wash system, I did drain the water between the deck fitting and the pump, which is housed in the same compartment as the bow thruster. I didn't want this pipe to burst having just fitted it! Most of the seawater, I imagine, drains itself out of the sail drive (SD50) and only a little remains in the engine/exhaust has a lower freezing point. I remove some of the floor panels to allow ventilation and also run a timed heater, that comes on early hours of the morning, to take the chill off. What engine do you have?
	Jon B 470e http://www.norse-king.blogspot.co.uk

Martin&Rene Members Profile Send Private Message Find Members Posts Add to Buddy List Vice Admiral Joined: 06 December 2009 Location: United Kingdom Status: Offline Points: 967	Post Options Post Reply Quote Martin&Rene Report Post Thanks(0) Quote Reply Posted: 02 April 2023 at 17:12
	JonB Open the seacock just before starting the engine, the water will not run out. The normal comment is that if you run the pump dry for more than 20secs then you risk damaging the impeller.
	Martin&Rene Hanse 341 Dipper Wheel steering, 3 cabin layout, normally based in Scotland



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