IPS D6 Cooling Mystery Deepens.

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oldgit

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Volvo Penta D6 and IPS.
Start engine(s) on mooring and at idle ( impellers changed twice) after very short spurt of raw water flow of raw water stops
Turn off engine(s)
Release lid on filter(s) ,air/gas escapes and filter fills with water . ????????
When filter full ,tighten lid, start engine and 9 times out of 10, impellor pumps water.

Now the weird bit ....
Once filters filled by water , see method above ....
With boat at idle on moorings or actually under way when throttles engaged to ahead lots of water flowing visible in filter................
Engage astern ...........and water flow simply stops.
Flow does not resume when ahead reselected.
Undo clamps, break airtight seal on filter, it instantly refills with water and off we go again.
Riser removed and as clean as a whistle.
 
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Possibly an air leak on the suction side?

Or could the raw water intake hose be collapsing under pressure when the raw water flow across the intake is disrupted in reverse?

Good luck with it.
 
On the working boat (Pershing 108, triple surface drives) when I engage astern for anything more than a boatlength (so, berthing or setting anchor), the amount of aerated water that gets sent under the boat, causes the air con system to pull air in. It goes into fault mode and the system shuts down. Bleed air (in a similar way to how you do it - crack the sea strainer open, air hisses and water rises, retighten, restart system) and all is good again.

I have to be extremely careful with the seakeeper gyro stabilisers, we managed to burn 2 cooling pumps out last season due to this. I since learned to shut the air con down before commencing manoeuvres, but the seakeepers require the cooling to be going for a period of time after you've shut them off. They're still spinning fast so I can't just shut them down unless I do it 30 minutes before entering the port. Of course, the stabilisers are at their most useful when going slow and waiting at a port entrance with ferries rushing past etc, so this isn't really an option.

Could it be, that the flow of water (or, somehow, air) under the boat by engaging astern is causing this?
 
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The "riddle wrapped in a mystery inside an enigma" is that the boat was only ashore for around 2 weeks and had been functioning perfectly prior to lift
The only thing in common regards both engines was that the impellers were changed, both new impellers have since been replaced with a second set of new impellers by the folks who sorted the IPS.
As soon as the IPS is put in reverse ( when secured to pontoon or underway) the cooling water drains out of the filter and does not return when ahead is selected with the throttles.
If want more strange on the port engine the flow does vanish if the helm is put hard over either to port or starboard while in gear on the pontoon. Cannot recall now which or wether throttles ahead or astern at the time.
The company who did the work have been extremely co operative throughout to the owner.
 
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jonbclarke said:
Possibly an air leak on the suction side?

Or could the raw water intake hose be collapsing under pressure when the raw water flow across the intake is disrupted in reverse?

Good luck with it.
Click to expand...
Both raw water hoses to pump and riser bypass exit hoses are in plain sight with engine running and appear to be in extremely good condition.
 
oldgit said:
Both raw water hoses to pump and riser bypass exit hoses are in plain sight with engine running and appear to be in extremely good condition.
Click to expand...
The water pick up goes through the lower gear case , I'd say there is something wrong between the lower and upper gear case to loose the flow when you turn the steering .
Was it a factory exchange unit ?
 
volvopaul said:
The water pick up goes through the lower gear case , I'd say there is something wrong between the lower and upper gear case to loose the flow when you turn the steering .
Was it a factory exchange unit ?
Click to expand...
Yes. Entire unit was changed.
The skipper did not want to wait for his own unit to be rebuilt.

IPS unit removed had serious wear on prop shaft ? and water contamination in oil.
New seals fitted last year.
 
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Front of engine driven by v belt.
Access not to bad, two of the bolts a right PIA and instead of a simple round plate, a fairly substantial entire cast moulding has to be taken off to change impeller.
1750390339736.jpeg
Suspicion now that the raw water pump only functions when either filter is filled via hose pipe or lid cracked which allows any pressure in block to be vented ....... but will not function, when any internal pressure generated by props in reverse , some how has pressurised raw water system.
Cannot find anywhere on the interweb any mention of the problem occuring elsewhere and thousands out there.
 
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Seastoke said:
Maybe try a Youngit.
Click to expand...
Well above OGs paygrade now and into the realms of authorised dealers with logo encrusted sign written vans in the club car park driven by chaps in white coats bearing magic boxes full of software and prayers offered to the hallowed offices in the sky of Volvo Penta.
We are not worthy etc...........
 
No doubt you have checked but it sounds like the pump is sucking air in.
We had a shaft drive do similar once, pump at front of engine long water intake hose to water inlet at rear of engine bay.
The hose was not adequately supported and dropped between supports.
You could see the air trapped in the hose where it drooped.
Put extra supports in and cured problem
 
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