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Thought I'd take the opportunity to post my experience with a recent engine overheat problem I had and what was done to resolve it. Apart from starting and stopping the engine and checking oil levels I had no practical experience with working on diesel engines. I found a number of very helpful videos on YouTube that related specifically to the model of Yanmar engine installed on Periwinkle.

So, the problem: after about 20 mins running, the water temp warning light and alarm came on. There was reduced water exiting the exhaust. Throttling back to idle, the alarm would cancel after a few minutes. Increased throttle and it came on again.

Fault finding. Lots of good info on various yachting forums. Checked that seacock open, water flowing into the strainer. All okay. Yanmar maintenance manual suggested the impeller, thermostat and mixing elbow could be the problem. So started with the impeller - okay. Thermostat - removed; inspected and looked okay. Mixing elbow - removed and took to Minards Yanmar Newcastle where a very helpful mechanic inspected and recommended I replace it due to pitting.

Rectification. Bit the bullet and bought a new mixing elbow (expensive!), thermostat and impeller and an anode just for good measure. Mechanic advised to do an acid flush on the engine to remove internal salt build-up that can cause overheating.
Removed and replaced the parts - the anode was almost non existent. YouTube was definitely my friend with videos on mixing elbow, impeller and anode. By chance, I removed a small rubber hose from the water pump to the engine block inlet. On inspection, I found a salt build up in both ends that would have significantly reduced the water flow and I believe was the prime cause of the overheat problem. Once cleaned and reassembled, did a test run and found excessive water leaking from weep holes of water pump body. Further research indicated that worn seals in the pump were the likely culprit. Back to Minards and picked up a set of seals (2 of) and bearings (2 of). Reasonably easy process to remove and replace with help of video. Refitted and another test run. All good.

So to the acid flush....mechanic recommended 2:1 mix of water to Hydrochloric acid in 10 litres of water; run through engine; stop for 10 mins; then flush with fresh water. Seemed very strong to me so reduced the ratio. Once completed, reconnected hoses and ran engine - all good, no leaks. Has been lousy weather in Newcastle and only got out this week to take the boat for a run. Ran for an hour with no alarm. So one happy chappy

Well done. Amazing what can be learnt from utube.
Cheers

Well done Curryhuose! Sounds like instead of allowing the problem to overwhelm you, you kept on doing problem solving and kept on keeping on until you finally got it all done. I think you should feel very satisfied with a doing a great job, especially when you started with no experience on diesel engines.

troppo

Hi Currryhouse,
Good article. Just for your information, there is a product called Rydlyme, which is able to be used to flush out all of the salt build up in your engine, without any detrimental impact on seals etc. I have used it and it works well (a better choice than Hydrochloric acid, in my opinion.)
I have only one problem in using this product - you have to remove the anode, as it will be eaten away in the flush. When I went to remove the anode plate (after only two years since last removed), the bolts rounded off - the manual says that the bolts are 10mm, but mine were not this size. To date, I am almost out of options, save for drilling in "easy=out" drivers and trying to remove the bolts this way. It has also been suggested that tacking on larger sized nuts to the existing bolts, using a welder, could offer an alternative solution. I will keep you advised of the results.
Kevin
KJD13,
Wayward Lady (Mk111),
Williamstown, Vic

Hi Kevin, thanks for the tip re Rydlyme. Will look into it. I've been told that vinegar is also an option. Sorry to read about your problem with the anode cover bolts. I wish you success with the repair.

Cheers, Neil