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The end of the engine?

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Thinking cap on....I wonder if a cyclinder liner has come loose? Is it possible to bypass the heat exchanger and run direct off raw water? If you have a berth, hookup a mains supply hose to the fresh water pump, run the engine then turn it on. Do you have a water scoop / filter (sea chest) on your skin fitting? Hiscock valve stuffed? Still thinking Matt..not much else to do in this weather when trying to get painting done.

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Chemical.did it again today. Shows nothing, but there must be a crack somewhere.

Today's testing shows the coolant level rising before the engine is even fully warm. It will rise quite a bit, then, if I turn the engine off, after about 30-45 secs it burps gas into the header tank, as if there was an airlock somewhere. But it will do that repetitively. I think it MUST be a compression leak...

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so  the heaps I have typed have gone because you cant go back to check..



 if definite,  unsubscribed and constant over heating...plus (sometimes but not always) bubbles in coolant..then cracked head or head gasket. (Block possible...)


Old motor...  Volvo...lots of effort to diagnoses ...new head gasket...


Do a balance of probability and cost exercise.




I dont like Volvo marine. Its terrible $ versus time.

I dont like sail drives. Its buckets of extras to solve little....but your stuck with it.

Regardless of what you find you have a very old motor. That means other things will go wrong.

Remember  you have two aims....least cost....most reliability.


I think you should do some dollar sums on where you are now.

I think I understand your position...and I hope you find the weird , easily fixed , coolant problem...

...but the last many times for me it never happened..

When I had run down all the sensible things.. ( right up to coolant water analysis, )

I had no choice. The engine had to be reliable. Not fast. not expensive and not even fuel efficient.

But reliable. 



(PS to the sailing nuts who think Im missing something..."Least cost" is just that.....its your least cost...more than just money...)

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Matt, I hesitate to chime in here but..

When my son bought his new boat a few months back he employed a mechanic to give the engine a complete service. The engine had not been used for a little while and was a 4 cylinder raw water through a heat exchanger cooled Perkins built by Mazda. Somewhat unusual I believe.

His engine exhibited the same symptoms as yours on startup - overheating, pressurising the header tank etc. Turns out there was an airlock in the engine someplace. The mechanics solution was to drain the coolant and then refill slowly with the engine running. Fixed the problem for my son.

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I’ve been thinking along the same lines as Chris’s post above


However I had the same engine that was giving problems in my previous boat and we couldn’t get on top of it, it was also a month out from the RNI, so bit the bullet.

I picked up the new engine and sail drive from Ovlov, had it installed and them back to commission it 7 days later all on my own.

Never regretted doing it, in a depressed boat market it’s a hard decision but when we sold because our boat was tidy and had a newish motor compared to most of the market it was a quick sale.

I know your probably not keen to sell anytime soon, however having a reliable motor is a great comfort when Murphy comes to play.

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Commiserations Matt,


Small consolation but at  at 10,000 hours you have had an outstanding life for that motor.

Also a head job will push the restored compression to the next line of defense, ie the rings or block, so its perhaps more than co-incidence to see this, post OH if there was a latent defect.


We recently had a self inflicted fuel supply blockage with our Perkins 4108,  found that eventually and fixed it, meantime had half the  system apart which caused failure of the Racor primary filter selection cock, 2 more weeks to suss that, 4 weeks later we are back in business. The silver lining is that we now know the fuel system back to front !

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Well, a month or two ago I posted a pic of my engine room. Was looking good! Unfortunately, things have not gone so well.


I have a volvo penta 2003T, 1998 model, with a 120S saildrive. The unit has around 10,000 hours. It has had some work done to it in this lifetime, including one rebuild.


BUT the other week, when I was supposed to do my RYA offshore masters practical test, it overheated on the way to Auckland. Had to postpone the test, returned to Gulf Harbour.



IT  this is identical to our experience. We had a 2003T in our chico 42. one day it started to overheat.  We replaced it with a d2-55 and have never regretted it. But we also found that the problem was the cap on the filler tank bottle.  a new filler cap solved the problem. the piece of rubber might be of the filler cap.

We sold the engine to a friend in Wellington, who has done some work to it and it is now in a shed in wellington, and is running sweetly.

so for $16k we got a new filler cap and a free engine. !!!!


Our heat exchanger and oil cooler were also pretty dodgy when we pulled the engine out 

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You could try removing the water distribution pipe from the cylinder head and clean it with muriatic acid along with the exhaust elbow, the heat exchanger, and other associated cooling pipes to remove any deposits that have built up. Even if there's flow it may not be working as it should as the build-up on the surfaces can impact heat transfer which reduces the cooling effectiveness. 

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Thanks CJ, yep, done all that, and replaced header tank pressure cap. Distribution tube was pretty clean, now spotless. Checked its orientation as well. What really gets me is why the combustion gas check in the coolant shows nothing.  I cant think of a reason for the coolant level to rise before the engine is even fully warm, except a combustion gas leak....

Perhaps the test fluid is too old or something, although it came from repco a couple of weeks ago.

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If the coolant rises before the engine is warm it would suggest air in the system so to me in my limited experience either the coolant needs bleeding or as you suggest it's coming from a combustion gas leak.

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Temps were recorded everywhere, that’s part of the normal process of finding a blockage. At the thermostat, at the engine inlet, engine outlet, heat exchanger in and out, and exhaust elbow. Whatever is it, I’m 98% certain it is not a cooling system fault, but an internal issue. Not worth fixing at this point, looking at new engine options. I’m going to do a comprehensive article about it on here, to assist any site users who are, or will be, facing an engine update.

I’m trying to get one of the manufacturers on board for a bit of a discount....

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