flushing a raw water cooled engine - how?

[Modulation]

I'm thinking of doing this on my 8 year old Yanmar 2gm20. I know it doesn't list it in the maintenance schedule in the manual but the flow of water going through the engine has reduced a lot in the last couple of years. I've also had it overheat 2 or 3 times last year without any obvious reason. I thought it could be the thermostat but I've been told these either work fully or not at all - and mine does open as the engine heats.
I'm pondering using an automotive flushing solution but it needs to be run around the engine at full operating temperature for 10 minutes minimum. That ain't so easy in a raw water cooled set-up when the "exhaust" water goes into the exhaust water lock and then back into the marina!
Any suggestions?

 

[VicS]

<span style="color:white">........ </span> Firstly I doubt if an automotive flushing solution will have much effect. I reckon you'll need an acid based central heating boiler descaler such as Fernox DS-3.

The brave, the impatient and the foolhardy use hydrochloric acid, obtainable as "brick cleaner"

You either have to have a willing helper with two buckets to return the solution to the start or rig up an electric pump. Probably good enough to get it warmed up and well circulated (It wont circulate through the engine until the thermostat opens.)then let it soak for a bit then circulate for a bit etc.

I would test the thermostat regardless of what you have been told. It should just start to open at the specified temperature which will probably be marked on it. It may also be marked with the temperature at which it is fully open.

 

[ShipsWoofy]

You could I suppose disconnect the inlet and exhaust and run them through a barrel of flushing solution?

Disconnect exhaust at elbow and attach hose to water outlet (where it feeds to the exhaust) though this will be very loud and fill the boat with exhaust. This will mean water will not be polluted with exhaust gases.

I know to put anti-freeze in if laying up for winter you just use a bucket full of anti-freeze and drop inlet to pump into it. Though this as you suggest means excess goes out the exhaust.

This is how I might approach it anyhow, though I think I would consider this in the workshop, especially if I was worried about the jacket, but then, my 1GM's are not that heavy??

 

[Poignard]

8 years isn't very old. My engine [BUKH DV10ME] is 25 years old and doesn't have blocked cooling passages.

Are you sure your water pump is in good condition? Or you may have a kink in the inlet pipe or a blockage in the inlet strainer.

 

[Tranona]

The first thing to do is to take off all the rubber hoses, particularly the by pass hose. You will probably find they are bunged up. Clean them out by squeezing them and shaking out the calcium deposits. It is unlikely that there is much in the water passages in the engine itself, but taking the anode out will allow you to inspect the water jacket.

 

[MrCramp]

You need to check the water pump first. They have a back plate on them that does wear. Take it off and look to see if it is worn. If so either reverse the plate (after removing any paint and cleaning the reverse side) or get the plate skimmed on a lathe.

This made a massive difference to the water fllow through my 2GM20.

 

[longjohnsilver]

Rydlyme is what you want. I've used it and it worked a treat.

Rydlyme

 

[Spyro]

[ QUOTE ]
Rydlyme is what you want. I've used it and it worked a treat.

Rydlyme

[/ QUOTE ]

According to the SPEC SHEET this is Hydrogen Chloride, Aqueous. which I believe to be diluted Hydrochloric acid, same as brick cleaner.

 

[barnaclephill]

According to the spec sheet it's only 5 parts per million Hydrochloric acid or less than 10% - I don't know the acronyms' meanings.

Hopefully a chemist (Vic?) could take a guess as to its ingredients from the properties listed on the data sheet. Ph3, completely biodegradable, etc. Surely something dissolves shells & lime that is 'household' enough to be cheap?

 

[longjohnsilver]

Don't really care what it is, all I can say is that it works very effectively and it's not expensive.

 

[Thresher]

I had the same problem come and go for years. The engineer pulled the pump outlet hose off of intake to the thermostat and we ran the engine, there was a strong flow, he put his thumb over the end and explained that there should be enough pressure to not be able to block the flow with your thumb, it was OK. It turned out that my exhaust elbow was scaled up with only a pinhole left to let the water through, I had been keeping the problem at bay for years by flushing brick acid through at lay-up.

 

[VicS]

I forgot about Rydlyme, I always do. Reports suggest that it is an effective scale remover but I don't know what it is. There is a lot of confusing "information" on the data sheets.

It appears to contain some HCl, they say less than 10% hydrogen chloride but how much less they don't say, presumably what they are meaning is that the HCl concentration is guaranteed not to exceed 9.99%. To put 10% into perspective lets just point out that the concentrated stuff on the laboratory shelf is a 35% solution of hydrogen chloride.
Hydrogen chloride I am sure you'll remember from your schooldays is a gas, ...remember the "fountain experiment" to demonstrate its solubility, and that hydrochloric acid is a solution of it in water

The figure of 5ppm for the TLV helps to confuse. TLV stands for "threshold limit value" and it is the maximum concentration in the air that is allowable for the duration of an 8 hour shift. (In fact it is old terminology, Occupation Exposure Limit is the term used now). One version of the safety data sheet also refers to the PEL or "permissible exposure limit". Whatever, it simply informs us that the maximum allowable concentration of HCL in the air in the workplace averaged over 8hours is 5ppm. It tells us nothing about the composition of the product.

They tell us that the pH is less than 3 but is "indeterminate due to fluctuating readings". What the hell is that supposed to mean. OK it is below 3 so it is acid, but for a strong acid like HCl you'd expect a much lower figure.

They also tell us that it is an "organic salt solution" but what organic salt they don't say. However, an organic salt will have a buffering effect on the pH and perhaps explains why the quoted pH is higher than one would expect from the implied HCl concentration.

I note that a maximum of 6 hours circulation is specified but there is conflicting advice about the temperature at which it should be used. One paragraph says 18 to 82C but two paragraphs later they say 10 to 24C.

They claim it is safe to use with a whole range of materials but you would not expect any problems with several of them anyway. There is no mention of it containing any inhibitors to prevent attack on metal components and they do indicate that some caution is necessary with aluminium, zinc or magnesium. It would be sensible to remove the anode from an engine first or at least be prepared to renew it afterwards. That applies to any acid descaler including Fernox.

My conclusion is therefore that it is based on hydrochloric acid but that its action is buffered by an organic salt. I would put it therefore between plain hydrochloric acid and Fernox DS3. Less aggressive than hydrochloric acid on its own but much faster than DS3.

 

[Spyro]

Thanks Vic, a much more informative post than my guess.

 

[cliffordpope]

You don't have to run the engine to get it hot. If you disconnect the intake and the outlet hoses and stick a funnel in each, you can simply fill the engine up with boiling water and your chosen agent. Leave for a few hours, then reconnect and flush out.

 

[wanderlust]

take the cover plate of the exhaust heat exchanger. The water ways are small and block up easily. The heat exchanger gets fured up. You may find that blowing the rubber hoses through and cleaning the heat exchanger solves the problem

 

[chriscallender]

It might be a bit tricky for him to do that on a raw water cooled engine /forums/images/graemlins/wink.gif

Chris

 

[Modulation]

Thanks all. I'll have a go with the Rydlime stuff if I am not succesful with dealing with the ehhaust. /forums/images/graemlins/cool.gif

 

[richardabeattie]

Whatever you do if you are going to run stuff into the engine the engine must suck it up - don't feed it in under any pressure!

 

[bhallworth]

I did this to my 2GM20 that I am currently refurbing just few weeks ago. After a lot of research I used Rydlyme. My engine is 15 years old and was heavenly scaled but I was amazed how well it worked. I used a small bucket with a 50:50 mix of water and hand cranked the engine to circulate the mixture through the engine. I used clear hose so you can see the solution bubbling as it works. I removed the bypass hose to the thermostat and blocked it off so the solution had to go through the engine. Then put the return hose back into the bucket. This way you can continually circulate the solution every 10 minutes or so. When all the bubbling stops inspect the water ways, it took me two doses of a couple of hours each. I have photos of how I did it if it helps?