Volvo penta 2003 freshwater system overheating and poor water flow at exhaust

[Pickard Corsair]

Hi I would be grateful for some advice on where to go with this, I have a Volvo penta 2003 fresh water cooled engine, currently the engine is producing little water through the exhaust despite, new water pump, cleaning and putting new seals on heat exchanger, changing exhaust elbow and running rhydleme (descaler) through the raw water system, flow of raw water seems good up to the exhaust elbow (which is why I changed it) heat exchanger getting hot so I assume fresh water is circulating but little water getting out of the exhaust and engine gradually overheating, could it be the exhaust pipe or silencer/ muffler blocked, I can blow through it okay with the kind of effort you might expect for a long pipe , lack of water followed heat exchanger service so not sure whether that could have caused it somehow but flow after it seems okay and elbow was in pretty poor condition so maybe that continues along the exhaust pipe? Thanks in advance for any help I have benefitted from many similar threads whilst getting to this stage!

 

[Bodach na mara]

I was going to suggest looking at the exhaust elbow as they are notorious for blocking but I see that you have renewed it. Did you check the pipe injecting the water into the elbow? They can also get blocked.

 

[Moodysailor]

Check the raw water pump. It could be that the pump body is worn which will reduce the flow considerably. The wear may not be obvious to an untrained eye, and will probably pump easily without any back-pressure.

I have forgotten if those pumps can be overhauled with a new cover and wear plate, but if this can be done, I'd recommend it.

 

[Spirit (of Glenans)]

I experienced a similar problem with my VP D1-20. After trouble shooting all the obvious components as you have described, I still had a weak flow from the exhaust outlet. Eventually I reasoned that if there was a weak outflow and no water was being lost into the bilges the problem must have been caused by a weak inflow.
Normally when doing the jobs that need to be done while ashore, I use a length of rebar to clear out any molluscs from the inside of the saildrive. Unfortunately, on this occasion I had inadvertently rammed a piece of mussel shell up into the seacock. After trying to rod it out mechanically I eventually blew it out by lung power. A dinghy pump could also be used. I should add that I had removed the end of the hose connecting the seacock to the pump and replaced it with a short length of hose that reached above the waterline.

 

[MoodySabre]

Perhaps the exhaust hose has collapsed. If there is lots of flow at the elbow but it is not getting away then be careful that it doesn't backfill the engine. That could be fatal (for the engine).

 

[Jamie Dundee]

Possible air leak around the raw water strainer can cause a weaker flow as the pump is sucking air.

 

[kalanka]

With the same engine overheating off Islay, the normal clearing of the intake filter did not work for me but when I eventually peered down the filter chamber and through the seacock there was not the normal greenish light (well, normal on a bright day). Poked a big screwdriver down through the seacock and pushed out an obstruction. Problem solved in full. Problems with circulation pump do cause overheating but are limited to the freshwater circuit and do not per se restrict the flow of raw water to the exhaust. Worth a try.

 

[Pickard Corsair]

Many thanks for all the responses, probIem now solved, I went through the system top to bottom, checking individual sections etc from sea cock to exhaust and muffler, I had been reluctant to take the heat exchanger off again having gone through the palava of taking it off and servicing it quite recently (clue as to issue!) and assuming that could not be the problem (plus the seals were all holding nicely) whilst I could blow through the HE and water flow seemed reasonable after it and before the elbow I decided to temporarily by pass the HE and see what exhaust water flow was like without it , the result was tonnes of water so clearly something was up, off it came and when I took it apart the problem was obvious, the seal at the front end with two holes for the raw water input and output had twisted out of line when last being sealed effectively blocking the input and output, easily solved and back on in no time (now I am familiar with the process) a classic case of user error but at least I now know the cooling systems top to bottom have descaled the whole system and replaced a well worn exhaust elbow in the process, thanks again for all your assistance

 

[Gwylan]

Well, if you'd waited I would have made that suggestion for a possible fault.

Don't have to ask why.

Happened in Dunkirk, I had a spare day and could clean the system and improve the water flow and run the engine cooler.
Day 1 order parts and buy de-calc from supermarket. Strip the heat exchanger and soak in de-calc.
Day 2 faff about waiting for parts. Most,y drinking local beer.
Day 3 the parts arrived at the Volvo dealer. Night of Day 3 all fitted and ready to depart. Flow worse than previously. Decide not to do night passage with dodgy engine.
Day 4 before decide to strip it all down tried blowing through the HE. Obviously one route is blocked. Disassemble and notice the pinched gasket.
Rest is history.

Why does the exhaust elbow get bunged up?

You can get the fresh water pump refurbished. Place in Cheshire.

The salt water pump is user serviceable, with care. Turn the sea cocks off first!!

 

[scottie]

Many thanks for all the responses, probIem now solved, I went through the system top to bottom, checking individual sections etc from sea cock to exhaust and muffler, I had been reluctant to take the heat exchanger off again having gone through the palava of taking it off and servicing it quite recently (clue as to issue!) and assuming that could not be the problem (plus the seals were all holding nicely) whilst I could blow through the HE and water flow seemed reasonable after it and before the elbow I decided to temporarily by pass the HE and see what exhaust water flow was like without it , the result was tonnes of water so clearly something was up, off it came and when I took it apart the problem was obvious, the seal at the front end with two holes for the raw water input and output had twisted out of line when last being sealed effectively blocking the input and output, easily solved and back on in no time (now I am familiar with the process) a classic case of user error but at least I now know the cooling systems top to bottom have descaled the whole system and replaced a well worn exhaust elbow in the process, thanks again for all your assistance

Yes the water flow through the stack is serpentine and requires the seal to correctly aligned at both ends

 

[Pickard Corsair]

Well, if you'd waited I would have made that suggestion for a possible fault.

Don't have to ask why.

Happened in Dunkirk, I had a spare day and could clean the system and improve the water flow and run the engine cooler.
Day 1 order parts and buy de-calc from supermarket. Strip the heat exchanger and soak in de-calc.
Day 2 faff about waiting for parts. Most,y drinking local beer.
Day 3 the parts arrived at the Volvo dealer. Night of Day 3 all fitted and ready to depart. Flow worse than previously. Decide not to do night passage with dodgy engine.
Day 4 before decide to strip it all down tried blowing through the HE. Obviously one route is blocked. Disassemble and notice the pinched gasket.
Rest is history.

Why does the exhaust elbow get bunged up?

You can get the fresh water pump refurbished. Place in Cheshire.

The salt water pump is user serviceable, with care. Turn the sea cocks off first!!

Thanks, the drinking beer and waiting for parts in France bit sounds quite good!

I only bought the boat last year and have been working through the engine generally serving and replacing bits, I fitted a new raw water pump this year as the old one was leaking like a sieve, the elbow was badly clogged with calcium/ salt deposits and general gunge and the exhaust interior looked in pretty bad shape coked up and rusted (pictures attached) it looked great from the outside so fortunate I was forced to do it on my watercooling journey of discovery!