Impeller cooling.

[vas]

share vyv_cox concerns and also slightly confused.
I'll just focus on the suggested use of a non-positive displacement pump for sucking water off even a 30cm pipe (doubt it will be closer than that)
I understand that this will only work if said pump is placed below waterline so it will be able to slosh about water and eventually moving it up to the heat exchanger (hopefully)
is this your plan? Even a sketch diagram would help. Don't confuse your useage to a closed circuit one on a car engine. not quite the same. Abrasive properties of seawater also rather different to nice glycol/whatever mix car engine coolant. Why do you think that bearings in the 25quid pump will be up to the job? Decent ss bearings and seals even on the smallest of sizes are probably about that, how come this one has an el.motor as well at that price? I know it's mass produced but so is SKF bearings, replaced my yanmar 2GMF ones wasn't that cheap!
I'd make sure the overheat and oil pressure switches/warnings are setup properly and working before embarking in this.

 

[ChromeDome]

Interesting idea, but when I look at the specifications and characteristics of a centrifugal vs. a positive replacement pump, I have a hard time seeing a centrifugal vane solution that fits my engines.

Sorry if I'm stating the obvious:
As mentioned earlier, an integral (car-type) pump is used to circulate coolant in the engine's closed cooling jacket, and this is done without any significant pressure requirements other than what the thermostat may cause.
The heat is transferred to seawater in a heat exchanger to remove the engine heat from the coolant.
For the heat exchanger, the seawater is drawn in through a seawater filter, through the heat exchanger, oil coolers, turbo and out into the exhaust. Pressure can build up depending on the free flow in the components.

Jabsco F6B impeller pumps are standard on my engines. The Toyota/Nanni engineers specify an output of up to 130 litres per minute - and no less than 110 at 2.5 bar (250 kPa) pressure - for each engine.



I have not been able to find a single 12-volt pump that meets these requirements. Hence finding two plus spares to carry is way more complicated than having a couple of spare impellers in the toolbox.

And I like to know that the engines are cooled when running. No wires, switches or fuses.

 

[oldgit]

That'd be £30 a year, or as the Aberdonian in me would think, 10p an hour wearing itself out!

On the other hand down here in civilization.
£30.00 ..........15 litres of fuel, an hours run time or perhaps 20 nautical miles .
Get it really wrong and its a good days boating gone, a long slow embarrassing tow home** and the worry its a eyewatering several £ K bill, even worser, the boat out of the water for a month or more ? and the wheels of Maritime repair grind exceedingly slow.

** from a friendly passing Dutch yacht on one particular occasion. Never did manage to track him down, did drive down to Ramsgate to try and catch him, assumed he went straight back across to home.

 

[vas]

Jabsco F6B impeller pumps are standard on my engines. The Toyota/Nanni engineers specify an output of up to 130 litres per minute - and no less than 110 at 2.5 bar (250 kPa) pressure - for each engine.

+1

and just to give some real data (from installed sensors) on my 2GMF (that's fresh water cooled with a heat exchanger mounted at the exhaust side of the engine), the little (circa 50mm dia) impeller pump produces 0.2bar at idle and 0.5bar at 3k rpm. keeping the generator engine at 62C at 3krpm (2pole 8kw geny) even with 28C seawater temp in Aug in the med.

V.

 

[jamie N]

share vyv_cox concerns and also slightly confused.
I'll just focus on the suggested use of a non-positive displacement pump for sucking water off even a 30cm pipe (doubt it will be closer than that)
I understand that this will only work if said pump is placed below waterline so it will be able to slosh about water and eventually moving it up to the heat exchanger (hopefully)
is this your plan? Even a sketch diagram would help. Don't confuse your useage to a closed circuit one on a car engine. not quite the same. Abrasive properties of seawater also rather different to nice glycol/whatever mix car engine coolant. Why do you think that bearings in the 25quid pump will be up to the job? Decent ss bearings and seals even on the smallest of sizes are probably about that, how come this one has an el.motor as well at that price? I know it's mass produced but so is SKF bearings, replaced my yanmar 2GMF ones wasn't that cheap!
I'd make sure the overheat and oil pressure switches/warnings are setup properly and working before embarking in this.

As stated, the system is installed and functions perfectly. The raw water comes through the stopcock and to an inline filter, then to the 'pumps'. So far everything is below sealevel, thus 'under pressure'. The pump(s) then distribute the water as directed by the thermostat relay, to exit via the exhaust/heat exchanger where appropriate. This is what a pump does. The pumps have no need to prime as they're under pressure from moment 1. The most important thing is having the engine now fresh water cooled, which would be a more expensive, less reliable and efficient system if one was to do it in a traditional manner, with a mechanical thermostat, an extra mechanical impeller pump, all fitted to a retrofitted frame on the front of the motor.
As an aside, motor manufacturer's have moved away from whirring belts and continually running mechanical pumps as a form of advancement; I'm not one to argue with them
The £25 quid pump is magnetically coupled, thus NO seals, a form of running on an underwater motor that I'm very familiar with. That is the motor that'll probably be fitted when the manufacturer's impeller dies. It isn't subject to any form of contaminated water: it's in a closed system with antifreeze and additives in exactly the same way as Toyota fit it to millions of cars.
If either of the diaphragm motors were to fail, I'd not hesitate to replace either with the same, or the Toyota item.
Chromedome's point is valid for his engine, which I believe is a far larger generator of heat than my RM90, for which 20l/min is ample within the coolant circulating the fresh water side of the motor. The 22kW heat exchanger, fed by the diaphragm pumps has proved itself ample on the raw water side.
Edit: This page from a pump article states:"Diaphragm Pump:Diaphragm pumps are more suited to moving thicker liquids such as sewage and muck.", even though it also states that air is more common than electric for powering them, but the principle is identical.
I sail in Scotland where we tend to have cleaner water, but having sailed (a lot) in Chi & Langstone Harbours, it's likely even more suitable there.

 

[ChromeDome]

Don't get me wrong - I do find it interesting and appreciate that you've found a solution to your quest. It just seem not to fit my needs.

As a note on the side my sea water strainers, impeller pumps, flow monitors and seawater cooled oil coolers are all above sea water level (just), so can be opened at any time without water ingress. Reassuring (to me), as Murphy's law indeed will make sure adverse events will happen underway rather than when sitting in the marina.

 

[PCUK]

I'm really looking forward to the final test when the diaphragm pump is fitted. Hope you'll remember to keep us updated after testing. I must admit I'm still not convinced but happy to be proved wrong. Cheers, Peter

 

[jamie N]

I'm really looking forward to the final test when the diaphragm pump is fitted. Hope you'll remember to keep us updated after testing. I must admit I'm still not convinced but happy to be proved wrong. Cheers, Peter

The diaphragm pumps are fitted, and are working AOK with about 50 hours of running. The only issue thus far, has been that I didn't secure them by their 'rubber feet', which led to a helluva noise. As soon as I refitted the rubber feet, it virtually eliminated the noise, or more obviously, the engine noise more than conceals it!
I'll cobble together a drawing of the layout, and post it, but "tempus est inimicus"........

 

[zulloboy]

I replace mine on alternate years, say every 120/150 hours. Why take the risk for such a small cost saving. It's why I use Volvo service parts rather than pattern ones. As a mechanic said to me "why risk a £20000 engine in order to save a few pounds?"

I'm with you Allan. Cooling pumps are such simple devices, but so critical that when they fail can cause horrendous problems way beyond engine damage.
I can't understand why anyone would not give theirs an hour or two of TLC once a year. At the very least, you'll know it inside out and be able to diagnose and fix problems very quickly at sea. I don't admire boasts of how many years since the last impeller change, I think it's just dumb.

Cheers, Graeme