Volvo 2003 water flow

[Gazza]

I'm hoping for some advice on a problem that has just shown itself on our Volvo 2003 28hp raw water cooled engine. It has run well for the three years we have owned the boat, and was running well when she was lifted out for a planned week or so just before the lockdown, so she has been ashore for a couple of months now. When she was lifted back into the water late this afternoon I started the engine as usual only to find no raw water coming from the telltale on the transom. It's very difficult to tell if water is coming out of the exhaust as it is virtually underwater at the very stern. There is good water flow through the inlet sea cock, I've switched the impellor and also confirmed that there is water reaching the impellor pump housing. I've also loosened the engine anode bolt in the block and there seems to be plenty of water pressure there. The anti-syphon valve is showing a good pressure of water when I loosened the top housing.
I haven't run the engine for an extended period to check overheating, although the exhaust temp. sensor seemed to be rising quicker than normal. My immediate thought is that this is probably due to the exhaust elbow being corroded/blocked but I've now had a chance to think about it at home (boat now back on the hard) and I think that the telltale runs from the anti-syphon valve which is immediately after the raw water pump and, therefore, shouldn't be affected by the exhaust elbow.

We haven't had any impellor problems, so it's probably not an impellor blade lodged in the valve.

Unfortunately the boatyard lifting/relaunch schedule is tide dependent and they are apparently working alternate weeks with the yard staff alternating with the engineering staff. With the tides here (Plymouth) this means that unless I get this sorted in the next three days or so, then I'll have to wait at least another week before relaunch.

Am I missing something very obvious? Any help gratefully received ………………….

 

[Catalina36]

If the tell tale is anything like that on some outboards it may just be blocked with a bit of salt deposit even though the main circuit is clear. Try checking that by prodding/flushing/dismantling.

 

[Cardinal]

I should try dismantling the anti-syphon valve to check that nothing in there is blocking the flow to your tell-tale. Impeller parts can hang around for years.
I would get the boat afloat anyway as there should be no need for any work ashore whatever is amiss.

 

[corinthmistral]

Previously had the same scenario on the same engine (freshwater cooled version.)
I took the exhaust elbow off first and it was largely clear. Not too difficult a job but you need a replacement gasket and sealant/red hermetite etc.
Next check was the heat exchanger - not sure what you have in place of this on the raw water version, but mine was choked with barnacles, mud and weed. So you may find a blockage in the system somewhere if the elbow turns out not to be blocked.
Other culprits have been a blocked pipe, or the interior of the pipe breaking down and causing a flap of rubber to obstruct flow.
I would systematically work from the impeller pump outlet to see where the blockage is.
Trust assists.

 

[corinthmistral]

Previously had the same scenario on the same engine (freshwater cooled version.)
I took the exhaust elbow off first and it was largely clear. Not too difficult a job but you need a replacement gasket and sealant/red hermetite etc.
Next check was the heat exchanger - not sure what you have in place of this on the raw water version, but mine was choked with barnacles, mud and weed. So you may find a blockage in the system somewhere if the elbow turns out not to be blocked.
Other culprits have been a blocked pipe, or the interior of the pipe breaking down and causing a flap of rubber to obstruct flow.
I would systematically work from the impeller pump outlet to see where the blockage is.
Trust assists.

Nb: the hardest part was getting the exhaust hose off; I took the jubilee clip off then used a flat head screwdriver and a hammer to wiggle/hammer/work around the pipe to break the rust and free it from the elbow. Once freed, it slid off fairly easily. When I put it back I used a liberal smear of water pump (thick) grease, to assist removing it another time.

 

[erich27]

We have a 2003 raw water cooled and have had two cooling water issues :
1. On the delivery trip from Ardrossan to Holyhead the engine overheated, eventually found the problem to be a worn out wear plate in the pump housing, replaced it and solved the problem !
2. When we lifted the boat out of the water for the winter lay up we didn't close the inlet sea cock before the boat came out and it resulted in an air lock which stopped the cooling water flow
Hope this helps, ?

 

[Gwylan]

We have a 2003 fresh water cooled.

Silly questions follow
From left field, is the water inlet clear? - some small birds think it is a great place to try to make a nest. Stuff a load of stuff up there, realise it will not work and bugger off. The exhaust outlet is even better, being bigger.

Is the impellor installed properly and doing the job?
Is the fresh water pump actually working ? - Turn the sea cock off, take the cover off the impellor and turn the engine over on the starter a few times. Is the impellor actually going around?

Is the lid on the anti syphon making a good seal?

An air lock can also be a pain. Start the engine, in the water, and briefly run up the revs. It usually clears in a few seconds.

The other advice regarding a 'step by step' approach to trace the water through the system is a sensible way to go.

 

[VicS]

I'm hoping for some advice on a problem that has just shown itself on our Volvo 2003 28hp raw water cooled engine. ..........

When she was lifted back into the water late this afternoon I started the engine as usual only to find no raw water coming from the telltale on the transom. ........
The anti-syphon valve is showing a good pressure of water when I loosened the top housing.

Am I missing something very obvious? Any help gratefully received ………………….

If there is good water pressure at the ant-siphon valve but no water coming out of the telltale Id say it must be blocked.
With an overboard "telltale" there should not actually be a valve in the anti-siphon device . it should simply be free running to the overboard outlet,

Disconnect the telltale and check it for blockage ........... If it is blocked it wont function as a siphon break and you run the risk of flooding the engine.

I think you must check that you are getting injected water into the exhaust........ check that the exhaust system is not getting too hot if you cannot confirm a good water flow

I think you must also check the engine operating temperate to be sure that it is not overheating

 

[duncan99210]

The OP mentions that his exhaust temperature sensor is showing a rapidly increasing temperature. That’s a classic sign of no water getting into the exhaust elbow. So it’s possible that there are two problems here: a blocked vent tube from the anti syphon valve and a blocked exhaust elbow.
I’d suspect a insect or similar in the vent pipe, but that’s easy to check by removing the tube from the valve and seeing if you’ve got water coming out: if you have that tell you two things. First, the pumps working and second you’ve got a blocked tube. If you’ve got no water at the valve, then the pump is the problem.
Water at the valve, exhaust temperature still rising, you’ve got a blocked exhaust elbow.

 

[VicS]

The OP mentions that his exhaust temperature sensor is showing a rapidly increasing temperature. That’s a classic sign of no water getting into the exhaust elbow. So it’s possible that there are two problems here: a blocked vent tube from the anti syphon valve and a blocked exhaust elbow.
I’d suspect a insect or similar in the vent pipe, but that’s easy to check by removing the tube from the valve and seeing if you’ve got water coming out: if you have that tell you two things. First, the pumps working and second you’ve got a blocked tube. If you’ve got no water at the valve, then the pump is the problem.
Water at the valve, exhaust temperature still rising, you’ve got a blocked exhaust elbow.

I missed that!

 

[ctelfer38]

I missed that!

As an added check - the water pump has a small cam secured by a stud screw. When that is old and worn it does not provide a high enough surface for the impeller to work at full efficiency. Your comment about your exhaust outlet suggests you need to adjust your vessel's trim to lift your stern a touch. The exhaust should be clear of the water and it should show a healthy amount of water coming out. Is your engine exhaust noisy? If so that would confirm a deficiency of water throughput. Hope this helps. CBT

 

[RAFFY]

Hi Gazza, I have had similar issues with a VP2003 several times over many years of ownership. The cooling system on a raw water cooled installation is quite simple. If the inlet is clear and the pump impeller is working well enough, then you should look at the exhaust manifold.
How do you know there is good water flow through the inlet seacock? Do you have an inline filter/strainer so that you can see the flow?
If there is no water coming out of the exhaust as you suspect, then the 'good water flow through the inlet seacock' must be going somewhere? I suspect it is hitting an exhaust blockage and can't get past it and pressuring the system - so check exhaust first.
As a previous post suggests, you can hear if your exhaust is 'dry', ie no water getting to it. If it is OK, you will hear the normal burble, burble of water being injected into the exhaust, but if your engine sounds just like a car engine, ie no wet burble, then I would certainly whip off the elbow and dig into the crud that will inevitably be present around the water injection hole. The difference between a dry exhaust note and a correct wet exhaust note is a good clue and is easy to spot.
Another area that I have seen blocked in the inlet seacock from a saildrive, but if you are confident you have good flow here then perhaps not the primary cause in this case.
Let us know what you find please.

 

[RIBW]

Hi,
My recent 2003 overheating: I found a fragment of pump blade had lodged at the input to the 'flute'. Crud had grown around it during my ownership and eventually blocked the cooling water input to the engine completely. If water can't enter the flute it can't take the direct route through the head to the multibend pipe and into the exhaust elbow OR down through the block and back up to the thermostat then to the exhaust elbow (via a calorifier if you have one).

I did a full engine flush with brick acid, including the elbow and the engine-block drain valve. (There was no need to remove the flute)
Cooling water throughput is now remarkably improved and very evident even though the outlet is on/below the waterline. I have also added a thermocouple on the thermostat output and a flow detector indicated by the spare lamp on the 2003 control panel. (There were plenty of spare wires in the engine wiring harness).
For those who like circuit diagrams - here's mine:-



Cheers and good luck
Bob

 

[Gazza]

Hi All,

Many thanks for the responses - very helpful as ever.

The small pipe from the anti-syphon valve to the skin fitting was blocked (as was the skin fitting itself) so I've cleaned all that up and it blows through with no problem. I then worked my was through the water system and eventually managed to get a good water flow through after cleaning up the exhaust elbow; this wasn't too bad but one of the inlet pipes was partially blocked. The end result, with a hose into the top of the water inlet, was that I ran the engine for about 15 minutes at varying revs. with no overheating problems and a good water flow from the exhaust.

My next puzzle is that since the old anti-syphon valve was in a bad way I ventured to Force 4 and got a new one; the puzzle is that, although this looks identical to the old one, there is no water flow from the telltale pipe at the top. I've removed the pipe from the unit to the skin fitting, but there's still no water flow, even though water is flowing through the valve to get to the engine. The spring at the top, under the cover, seems to be operating. Now that I'm sitting at home, after a much-needed shower, I'm wondering if there are two sorts of anti-syphon valve - a spurter and a non spurter (if you see what I mean).

Can anyone shed any light on this - I'm going back in the water tomorrow anyway, with a short trip to our home berth, but I'd like to sort this out anyway.

Thanks again,

Gary

 

[cpedw]

Some anti-syphon valves include a non-return valve so that, with the engine running, there is no flow through the vent pipe. When the engine is stopped, air can flow through the vent into the coolant pipe and break the syphon.
They are tidy - no flow out of the vent. But the vent pipe is prone to clogging, as you found, but there's no warning of that. The simpler, more reliable but less tidy type, is simply a T with the vent being much smaller bore so that most of the cooling water flows where it's needed but you can readily check that the anti-syphon is working.

Derek

 

[VicS]

My next puzzle is that since the old anti-syphon valve was in a bad way I ventured to Force 4 and got a new one; the puzzle is that, although this looks identical to the old one, there is no water flow from the telltale pipe at the top. I've removed the pipe from the unit to the skin fitting, but there's still no water flow, even though water is flowing through the valve to get to the engine. The spring at the top, under the cover, seems to be operating. Now that I'm sitting at home, after a much-needed shower, I'm wondering if there are two sorts of anti-syphon valve - a spurter and a non spurter (if you see what I mean).
Can anyone shed any light on this - I'm going back in the water tomorrow anyway, with a short trip to our home berth, but I'd like to sort this out anyway.

AS Cpedw says there are two types

One has valve in the top , which closes with water pressure under it, but opens again when the engine is stopped to allow air to enter to break the siphon. It does need a hose connecting it to an overboard outlet.

The other has no valve but instead it connects to an overboard outlet that pees water all the time the engine is running. Or it can be routed to a cockpit drain to make a more visible telltale ( It will also make you pee more frequently until you get used to it)

You have bought the one with the valve but you can remove the valve innards if you wish to convert it to the peeing type.

(The valved type must be checked and cleaned periodically to make sure it is not blocked and functions correctly. If the peeing type is peeing you know its OK and not blocked)

 

[Gazza]

Hi All,

Many thanks for all the advice - anti syphon valve sorted this morning and boat back in the water this afternoon with very satisfactory rate of peeing from the telltale and generally better water flow.

I noticed that someone mentioned the trim of the boat as a factor in the low level of the exhaust. All Moody Eclipses have this feature and it has caused much discussion on the owners' club forum - the consensus is that it's not really a problem but makes the telltale more important. Retrimming the boat to get the exhaust out of the water would probably resemble something like the last moments of the Titanic...………...

Once again thanks for the help.

Gazza