Annoying Leak.

if you cannot find what IS wrong, then use whatever processes you can to find out what is NOT. Basic fault finding is your friend. :encouragement:
 
Flica said:
Interesting that you feel compelled to send your raw waterpump away for replacement of seals and bearings (as it's as big a job to do one as the both on the two waterpumps I've had)
With the frequency of leak, that the raw-water cooled Yanmar 2GM suffered with its Jabsco pump I got in the habit of carrying a spare pump. To take off the faceplate meant you had to dismount it!!
The far superior Johnson pump on the 3YM goes much longer between replacement impellers (about 500-700 hrs), but I still have a spare pump.
The only real problem is extracting the bearing, but I've found that if the impeller has gone, the seal is not far behind and the bearings go as soon as the seal leaks.
Rather than buy the replacement pump as a Yanmar, I bought the bits from Johnson with a cost of about 20% (that included body and shaft) of the Yanmar derivative. On coming to the pressed steel pulley (an engineering miscarriage) I had to cough up more than the rest of the parts had cost.
Though it now only takes about 90" to change impeller, (changing the water pump only involves two bolts, not 6 as does taking off the faceplate).
I can then re build the pump, at my leisure, in stillness and using relevant tools such as a vice.
Click to expand...

Now I a interested in this Johnson pump and how to obtain one. I don’t have a 3 YM mine is a 3 GM and quite frustrating.
It runs well enough but parts are expensive and Yanmar seem to keep a tight control on them.
For me localy the difference in cost between a rebuilt water pump and a new one is quite significant. The awkward bit about getting a rebuilt pump is the shop wants the knakerd one first. So my plan is to remove when I haul out.
 
A problem I have had and no one has mentioned with the Perkins version,is the rubber end caps leak sea water into the heat exchanger and comes out the over flow pipe just under the 'radiator' cap,so check the jubilee clips on either end of the heat exchanger.Mine didnt leak at low revs but when revs increased it came pouring out.
 
peteK said:
A problem I have had and no one has mentioned with the Perkins version,is the rubber end caps leak sea water into the heat exchanger and comes out the over flow pipe just under the 'radiator' cap,so check the jubilee clips on either end of the heat exchanger.Mine didnt leak at low revs but when revs increased it came pouring out.
Click to expand...

The OP's MD2010 is similar.

The increase in "leakage" with increased revs would prompt me to check the exhaust injection point for restriction of flow. There really should not be such build up in pressure of the raw water that this will happen. least ways not to exceed the pressure of the coolant once up to running temperature.
 
Uricanejack said:
Now I a interested in this Johnson pump and how to obtain one. I don’t have a 3 YM mine is a 3 GM and quite frustrating.
It runs well enough but parts are expensive and Yanmar seem to keep a tight control on them.
For me localy the difference in cost between a rebuilt water pump and a new one is quite significant. The awkward bit about getting a rebuilt pump is the shop wants the knakerd one first. So my plan is to remove when I haul out.
Click to expand...

Unfortunately your 3GM probably has a Jabsco pump (my 2GM had one of those) - it's quite difficult to get anything from them at anything but full price. ASAP Supplies are usually a source of parts at a competitive price.
Fortunately for me, I had in the past, done quite a bit with a Johnson Pump subsidiary, so was able to seek advice on how to get the parts economically in the UK, I just went through their parts dept - after being given a list of the part numbers in the pump. I note that a replacement raw water pump is now listed by Yanmar at over £300 - when I bought the pump parts, the body cost £24, the shaft £16 but Yanmar demanded nearly £70 for the pressed tin pulley.
I must stress that, more than anything else it's E P Barrus' policy which keeps Yanmar parts prices so high in UK - for things like injection elbows it's cheaper to import from the US even paying the duties and VAT. However if you have a friend who doesn't mind putting it in his hold-luggage....
You could swap pumps -
 
LittleSister said:
If you can't see (under) the pump when the engine is running (and do be careful when it is), can you wedge or tie a piece of dry cloth under the pump while the engine is stopped, run the engine for a bit then stop it, then remove the cloth to see if is soaked?
Click to expand...

I have it on good authority (Tim at Malahide Boatyard) that blue paper washroom towels are excellent for indicating these kind of leaks.
 
I would agree with the earlier suggestion of a leak at the siphon break valve. They regularly leak and are a service item.
 
david_bagshaw said:
I would agree with the earlier suggestion of a leak at the siphon break valve. They regularly leak and are a service item.
Click to expand...

Would be seriously worried if one leaked that amount of water - and would be immediately obvious given the position of the valve. I have had 4 such valves, two Vetus and 2 Volvo and never had a drop come out of any of them.
 
Because it's always nice to get some closure on things, I thought I'd mention what happened in the leak department.

After a couple of weekends where the water level in the engine bay got to the point where i was pumping out every 15 minutes, and having done almost all the things that I could (including checking the water pump on the engine - which turned out to be fine) and sealing up a tiny drip from the exhaust I decided to hang myself upside down and peer into the aft of the boat with a torch whilst heeling.

In hindsight, the solution was so mindblowingly obvious that I am suprised that even I with my newbie inexperience didn't see it.

The Prospect has 3 through hulls that are above the water line at the rear of the boat, situated under the rear of the hull but not under the water, only touching the water when heeling or under power (both times when the aft of the boat dips slightly), through these 3 through hulls exit the exhaust, cockpit drains and manual bilge.

Having carefully examined these through hulls out of the water externally and on the mooring internally (as best I could at arms length) there appeared to be absolutely no issues, however - on inspecting them when sailing by dangling upside down and using a torch to peer into the depths I was able to see a disturbing trickle of water coming from two of the through hull areas.

On arriving back at the mooring I asked Wicor to pull her out the following day and got a truly astonishing chap called Rob to go and wriggle in and have a look at the through hulls, a job that I physically couldn't do (dimensions and all that).

Turns out that 2 of the through hulls broke off in his hand, the pipes were rigid and split and I was lucky to not have a bigger issue.

Rob replaced all 3 with new fittings, new hoses and made good. Predictably - the boat now doesn't have an annoying leak in the engine bay area...

Moral of the story : lose a few (several) stone and get down inside the murky depths to inspect things like this rather than viually checking from a distance. It is however interesting to note that I had previously dismissed the through hulls as an issue as they had always come up as ok when on the mooring, it was only when the boat was in motion that the ingress was happening and I was very quick to blame the engine.
 
A useful tool to detecting leaks around through- hull fitting is blue wiping paper or blue paper towels. Wrap a piece around suspected (or u suspected) fittings before going sailing and then examine after the boat has been heeled/pitched. The presence of moisture will be instantly indicated. This advice was given to me by the redoutable Tim, of Malahide Marina.
 
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