Vetus water strainer

[bob26]

I have a vetus water intake strainer - the greay plastic type with a clear screw-off lid. The instructions say fit above the water line level - presumably to allow you to open it to clear it it clogs without a waterspout to contend with.

In fact it never seems to have much water in it at all when the engine is running (and none at all when its not). Is this normal. The engine shows no sign of overheating and water emerges from the exhaust in what seem like the normal satisfactory globs to me. So does it matter? I've tried tightening the lid etc to ensure there's no air blead and one of the advnatgaes of this kind of strainer is that as its situated directly over the intake seacock so I can actually look down the intake pipe and see clear water below so I know that's not clogged up.

I guess its possible to have it too high - or is it just that the impeller only shifts a set amount of water so there is no extra suction to lift more than exactly the amount required?

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[TheBoatman]

Bob
If your engine is not overheating then leave well alone.

However, I look after my YC boats and I have fitted 2 Vetus strainers to 2 identical engines (Yanmah 3GM30) and one puts out more water than the other. I can find no logical reason for this only that one is fitted lower than the other. The one that puts up the most water is the one fitted on the water line. I do find your comment about it being empty a bit strange as the Vetus pulls water up through a pipe which is extended to just below the cap so you should have some water in the strainer before you start.

The bottom line is if it's working OK leave it alone?

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[MIKE_MCKIE]

I have a similar setup & normally there are a few bubbles in the strainer wizzing around to show that water is flowing through the strainer. However recently on a long motor run from Brighton to Portsmouth my crew had a look & shouted that there was no cooling water is the strainer. Despite there being no hi temp alarm going off we shut down for a look. Having checked the sea suction (clear) I then took the impellor cover off, & lo there was nothing wrong with it! (Having only run for about 10 hours since new I would have been a bit cheesed off if otherwise!!) We started up again, & sure enough there were bubbles in the Strainer wizzing around. BUT after about 20 minutes they had all gone, giving the impression that the strainer was totally empty, & at first glance, giving me heart attack!
I am now looking for several small plastic balls/shapes to stick in the strainer, to indicate water flow during use. They obviously need to be fairly robust, as I dont want fragmented plastic going through the system, but light enough to float and preferably of nice visible colour, ie red/orange/yello whatever. Any suggestions gratefully received.
Cheers
Mike

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[brianhumber]

Your question is connected with your seawater pump throughput which in turn is governed by the laws of fluid mechanics.
If the throughput of the cooling pump is big enough then it will take the trapped air in the filter with it.
If I run at less than 1,500 revs the air stays in my filter. If the throughput is increased by running at over 2,000 revs then all the trapped air is drawn through the system and at first glance in clear water you cannot see anything but the filter is of course completely full up of water- so the answer is as long as the seal is good its does not matter about this trapped air in the filter.
If your pump, pipes and lid are 'tight' then the water should stay in the filter dropping only a few mmm when the engine is not turning even with the seacock on. ( Like the trick of raising a upside down beaker full of water from a bucket, the water stays in the beaker unitil the air rushes in when the beaker rim reaches the surface)

My filter and lots of other engine installations have this vetus filter at the top of the engine compartment, as you say this makes getting rid of any weed a 2 minutes dry job rather than scabbling around at the bottom of the bilge. I also tend to leave a small frond of weed in the filter as this tells me instantly the flow through the filter is still good at night when i check the engine compartment every couple hours on a windless channel crossing

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[Dave_Knowles]

I am not certain you should worry if all else seems OK. I have just fitted a Vetus strainer (not tried it yet due to major top end rebuild) because Volvo in their wisdom put the strainer after the water pump. As a result I have had to replace the pump at £217 plus VAT.

Up to now though the strainer I have (the Volvo standard one) has no means to see what is happening as the top is not see through. I have always used the temperature gauge and a quick check at the back to tell me if anything is wrong and that seems to have been OK for three years.

Dave

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[broadcaster]

Hi,

Mine has been in the boat for over a year and there is normally no water in it when the engine is off and when it is running there is a constant stream. The filter is never full of water though.

If you wanted it full of water you would have to bleed it first, but it wouldn't make any difference to how it runs. If fitted above the waterline as recommended, then it will not fill up with water and it is a safety measure so that you can remove the lid without sinking. That's why you need the seal on the strainer to draw the water through.

Andy



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[snowleopard]

there will always be a bit of air entrained in the cooling water. this finds its way into the strainer so the strainer will always be full of air.

under normal conditions you should expect water to come up out of the intake pipe and go straight down the outlet pipe. a certain amount of air will naturally go down through the pump but that causes no problems.

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[TheBoatman]

Mike
I can't understand why you want to put little balls in yer strainer just to see if theres water in it? Surely just as quick a method to see if the strainers blocked is to take a quick squiz over the transom to see if the waters coming out, if it is, yer strainer's working<s>

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[jfkal]

As long as the lid seal is tight no problem. Mine is always empty when the engine is off. But has a little fountain in it once the engine is running. Check the seal every couple of months.

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[MIKE_MCKIE]

Hi Peter,
Want the little balls, as I have an overhanging transom & the exhaust is a long way forward of the back end. Need a neck several feet long to get a half decent squint at the exhaust, & if more than 2 people in the cockpit the exhaust is at/under water level anyway. Also being half blind without the specs, always a little reluctant to hang upside down over the back, as the specs tend to go for a swim (mainly because I can't abide those bits of string that are supposed to hold them on)
All these excuses, I'm just damn lazy & it's easier to look at little balls than get off my backside to squint over the back!
Brgds

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