Raw water system failure

[camkorn]

Hello !

The warning light for the raw water cooling system has started to come on when we try to start the engine of our boat. It is a westerly pageant with a 13hp Vetus engine.

There isn't very much water coming out of the back of the boat. We have tried cleaning out the filter ( there wasn't much in it), and also we replaced the impeller. Neither of which have worked. We have also checked some of the pipes for blockages but can't find anything!

Is it possible that the anti-syphon could have failed? If anyone has any ideas what could be causing this problem please let me know!

Thanks,

Clare.

 

[nigelmercier]

Could be marine growth in the inlet. One way to check is to disconnect the hose from the (closed) seacock and let it suck from a bucket of water.

 

[theoldsalt]

Hi Clare,

Check the exhaust raw water injection point for partial blockage.

You will probably need to remove the injection fitting from the engine for a full examination. It is usually carbon build-up that causes the blockage which can be carefully removed. Check also for corrosion as this sometimes happens as well, making a replacement fitting necessary.

 

[ga1135]

I have similar issue recently and finally found that the thermostat was jammed hard and then replaced. Try check the thermostat in your engine too.

 

[Pasarell]

I had a similar problem earlier this year and went through the same process as you without any real success. In the end I bypassed the raw water pump and put an electric pump with a known output in the line which solved the overheating and so narrowed the problem down to the pump. The face plate on the pump was a little worn but I hadn't considered that an issue however polishing it smooth solved everything. Water output increased considerably and to an extent I would not have considered possible.

 

[nigelmercier]

Check the exhaust raw water injection point for partial blockage... Check also for corrosion as this sometimes happens as well, making a replacement fitting necessary.

This is also likely.

When I cleaned my exhaust elbow I put the screwdriver through the side of the fitting, the metal was paper thin. Expensive, but better for it to fail while you have it in your hand.

 

[jon711]

Sounds like it might be scoring on the pump endplate to me, try turning the endplate over and see if that cures it, if not then it may be a blockage in the inlet. Doubt that the anti-syphon has any bearing in the matter. Is it the original endplate or a speedseal? I have heard of some reports that the speedseal O ring can be damaged causing similar symptoms, but you normally notice a drip from the endplate first...

Jon

 

[PetiteFleur]

This is also likely.

When I cleaned my exhaust elbow I put the screwdriver through the side of the fitting, the metal was paper thin. Expensive, but better for it to fail while you have it in your hand.

Ditto! That's what happened on my Perama 20hp some years ago, interestingly the (identical) VP replacement was cheaper!

 

[charles_reed]

Assuming that yours is a raw-water cooled engine - I'd start at the beginning, take off the raw water pump and check it manually for suction. In my experience that's the most likely cause of problem and usually due to a worn faceplate.
Then check all the hoses, from inlet tap to engine cooling point, for collapses or blockages.
If all is OK, only then check the water injection elbow after the anti-siphon.
I found it worth carrying a spare raw water pump and still have one with a new engine.

 

[camkorn]

Hello!

Thank so much everyone for all your replies.

The faceplate on the impeller appears to be even and smooth so that doesn't seem to be the problem. There aren't any kinks in any of the pipes and all look in excellent condition from the outside (the engine is only 6 years old). We cleaned out the anti syphon and that appears to be fine.

When we went today we were feeling confident that we would find the exhaust elbow and that would be it fixed! Sadly we can't even locate it on our engine - there is nothing in the manual to show where it is and nothing visually apparent! It's all turning into a bit of a nightmare :-(

 

[prv]

Sadly we can't even locate [the exhaust elbow] on our engine - there is nothing in the manual to show where it is and nothing visually apparent!

The exhaust hose must be connected to the engine somewhere!

Pete

 

[vyv_cox]

When we went today we were feeling confident that we would find the exhaust elbow and that would be it fixed! Sadly we can't even locate it on our engine - there is nothing in the manual to show where it is and nothing visually apparent! It's all turning into a bit of a nightmare :-(

Follow the rubber hose from where it exits the engine, on many makes at the thermostat housing, going aft until it Tees into the exhaust pipe emerging from the back of the engine. That is usually referred to as the manifold.

Slight confusion about exactly which engine you have. Is it fully raw water cooled at only six years old? Does it have a heat exchanger, like this engine? http://www.vetus-shop.com/vetus-m202-mitsubishi-engine-12hp-fwc-zf10m-2051-p-2390.html

 

[camkorn]

Does anyone know if there is a separate thermostat for the raw water system? There is one on the main engine block but I thought this one just monitors the temperature of the coolant. Sorry I am being so vague - I don't know much about engines!

 

[camkorn]

Slight confusion about exactly which engine you have. Is it fully raw water cooled at only six years old? Does it have a heat exchanger, like this engine? http://www.vetus-shop.com/vetus-m202-mitsubishi-engine-12hp-fwc-zf10m-2051-p-2390.html

Hello! - The engine is the same one as in that link.

 

[theoldsalt]

Camkorn,

You stated that your engine is a Vetus 13hp diesel so it should look like this one.

http://www.abcpm.co.uk/downloads/engines/vetus/M2D5.pdf

If so, then the heat exchanger is at the top of the engine with the "V" embossed on it. The hose that exits to the right goes to the exhaust and that is
the raw water injection point that may be partially blocked - often cause by long term running of the engine on light load creating poor fuel burning characteristics. Diesels like to be run on heavy load, typically 80% of peak revs.

 

[vyv_cox]

Does anyone know if there is a separate thermostat for the raw water system? There is one on the main engine block but I thought this one just monitors the temperature of the coolant. Sorry I am being so vague - I don't know much about engines!

Your engine is indirectly cooled, which means the seawater cools the coolant in the engine via the heat exchanger, similar to a radiator in a car. If the engine is overheating and the seawater flow from the exhaust is low it indicates that there is a blockage somewhere in the seawater flow. It could be that there is some foreign material in the upstream side of the heat exchanger or that the manifold is blocked up with salts.