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?

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

Could the sea water strainer be clogged with seaweed etc? Maybe the new impeller failed?

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.

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.

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.

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.

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!

What engine do you have?

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.

The trip from lowering into the water to the windward side of the pontoon at the marina, would've been 5 minutes including a change from forward to reverse and an increase in revs until control was mine. Removing the impeller to check showed no signs of damage, but I did coat it in the grease that came with it.  The trip from the marina pontoon down the river to my home berth was about 10-15 minutes, I noted no change in engine noise, which without the water going through the exhaust was not 'normal'.

I'll not get to the boat till next weekend.  I learnt years ago from an old mechanic, spark, fuel, air and trained as an Engineer to think methodically, so I'll work from the sail drive intake to the exhaust outlet. I know that the sail drive is not blocked as water poured out when the hose was discharging, so its from the strainer to beyond.

Mine started to play up & I noticed that the pump cover plate was scored & worn. Although seemingly minimal, this will allow air to pass when trying to get the initial syphon going. My temporary solution was to clean the paint off the outside of the pump cover & very lightly abrade it so it was flat & clean. Then turned it round, back to front, & re fitted it. Problem solved.

No way would I pay the ridiculous price for a new cover, so I purchased a piece of brass for £3-50 which is enough for 2 covers & cut & drilled & fitted that. Although the original Volvo cover is shaped it need not be & the screw holes follow a circular pattern. I cut it with a hole saw with the centre drill removed.

Some covers have a neoprene rubber seal. It may be worth looking at that & getting the cover closer to the vanes.

The kit comes with a new O ring, which as a matter of course I change, I did look at back the of the plate and noticed some unevenness. On the yanmar the plate has inscriptions written on it so turning it over would probably be worse.

When I return at the weekend, I'll inspect more closely, see if there's anything that may cause an air leak first, as that's an easy check. I also tighten the bolts in an opposing sequence so not to load one corner at a time.

Thanks for your response.

Last time I was in Bradwell I arrived at 0500 helping my friend deliver 'Escalon' and I may be back with his new purchase.

Well if you come in a Hanse there is a rule about flying a "My Hanse" forum flag. Dave Holby of this forum used to sell the flags, but he has not mentioned them lately.

I think it may be time to resurect the practice. I could do with some shots of other people's finest whisky

If you do not know about this, then I am sure a search will show it up. Perhaps we should give Dave H a nudge. There must be a demand for more flags, now there are so many more Hanse boats about.

But I did solve the problem.

I traced the water pipes from the sail drive through the system and the water comes into the impeller from the right and discharges to the left!

I had set the blades assuming it went from left to right, so it was trying to push water rather than draw water.  I did find that many of the jubilee clips took a few turns throughout the exhaust, assume that vibration over time loosens their grip.

Both Johnson and Jabsco do a 1028 or whatever replacement but it doesn't have the one threaded side for ease of removal.  So as not in a rush I'll wait till the correct one arrives from Johnson.

I thought I had resolved the problem but we went out the other weekend and had to run back to tie up with an engine reaching 105C.

On inspection the new impeller I had replaced during the winter maintenance had shredded with no splines.  I spent a couple of days removing them from the heat exchanger, can never understand why manufacturers use Allen key bolts in places that is difficult to get to.  At least with a traditional bolt you have a chance to get a socket on it.  However, I still couldn't get water through the system.

Turns out that Yanmar provide a wear pack!  This is a space washer that fits behind the impeller to push it against the plate keeping the vacuum!  I bought a new plate as well.

This I fitted and the system is back to normal.

So the top plate is the new one and the bottom the worn one, worn by the actions of the rubber impeller, who says stainless is stronger than rubber.

I now have a filter basket almost full of water at 1,500 rpm with discharge out of the exhaust almost hitting the pontoon.

May I kindly ask how many engine hours do your boat have?

He was built in 2007 and we bought him second hand in 2010, the Yanmar instrument panel isn't the best and as such the hour meter stopped working as did the tachometer and I've since replaced the whole system with my own instruments and warning lights and ignition.

The plate is original.

Since ownership the engine has mainly been used to move in and out of marina's/ anchorages with occasional long runs on windless days, 2,200 rpm cruising speed.  We did get caught out rounding Alderney and had the revs about 3,500 for several hours rounding the corner into the harbour. But with Covid and one thing or another the last few years we've not really been anywhere.

I checked the filter basket housing and that was solid no cracks or air leaks from the O ring, jubilee clips or cuts behind the clips all proved negative.  I took the inlet off the basket and fitted it directly to the inlet of the impeller, careful as this is below the water line, so expect water ingress. This removes the need for the pump to created a negative pressure to draw water in and with the positive pressure from being under the water line the pump worked happily pumping water out of the exhaust.

If you're struggling to get water through, having learnt what I have, I'd smear Vaseline over the front side of the plate and switch it round, so the outside is in, yes there's inscriptions engraved on the outside, but these are shallow compared to the 'gouging' my plate has suffered.  This should improve things but will guide you to locate the issue.

Yanmar provide a wear kit, a spacer washer to push the impeller against the plate, but at a sixth of the cost of the plate itself, just replace the plate.  I'll keep the old plate as I might just polish out the inscriptions and have a spare.

Thx.

The reason for my question on run time was to get an impression about when an engine would require a new wear plate.

My boat engine just passed 1000 hours

But this will of cause depend on how dirty/Sandy the sea coolant water is.

Were there any Yanmar bulletin about measurements for the clearance or when a new tearplate is needed?

Obviously its a slow process of wear and so you don't notice it.  The usual is to remove the basket at the end of a trip and clean any muck out, so engine off.  Just see what the level of water is next time your on the boat for a set rev, at 1500rpm mine is now almost full with water splashing the top and keep an eye whether it starts to drop as the vacuum within this negative pressure side of the system drops.