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Old 08 June 2007, 02:41   #11
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Update

Engine now in bits;

Head gasket ok
Powerhead gasket ok

No other signs of areas where obvious oil "water" mixing can take place. However, the oil samples taken are now dark in colour there has been no separation into oil and water and it still reeks of unburnt fuel.

What did the oil look like in the engines that were "making oil"?
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Old 08 June 2007, 05:06   #12
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In the engine I had that was 'making oil', the oil looked normal if a bit runny - I don't know about o/b 4 stroke oil, but the stuff used in bikes is 'natural' (ie crude based rather than synthetic) so the petrol mixes with it normally.

The dark colour could be as a result of carbon deposits being washed down from the bores into the sump?
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Old 08 June 2007, 08:46   #13
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It's unlikely that the fuel will be running freely into the engine if the fuel tank is lower than it. I don't know your engine at all but it was a problem commonly associated with a leaking diaphagm on a camshaft driven mechanical pump. It could be a clue...or not.
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Old 08 June 2007, 09:34   #14
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Gadzooks JW! How could I have missed the obvious to check. I'll see if this can be verified. It sounds logical in terms of a ready route to put fuel into our oil. The miss fire we experienced before this started still seems a little at odds, or just not connected. Next step is see if we can have the oil analysed.
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Old 08 June 2007, 14:47   #15
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Its so cheap to have the oil analysed it would of been the first thing on my list of things to do. It can show you problems befor thay do to much harm. like bearing failings.

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Old 09 June 2007, 02:54   #16
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The Yamaha problem had something to do with fuel/air blow-by past the rings into the crankcase, where due to lower temperatures from low speed operation, the fuel condensed out (or something) and mixed with the oil. Higher speed operation caused a rise in temperature that alleviated the problem.

It apparently takes a while for the level to rise noticeably, but it's happening enough that I've heard of it from several different sources. As I said, the first line fix was a hotter spark plug. I don't know off-hand what else was done to correct the problem.

Sorry, Simon, I don't know what the fuel contaminated oil looked like, but the smell should be a fairly positive indicator. The remaining question, of course, is how it got there.

You can hit The Hull Truth forum (thehulltruth.com) and do a search for "making oil"; you should get quite a bit of information.

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Old 10 June 2007, 07:29   #17
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Cheers jyasaki,

Trolled through thehulltruth and will be pursuing their fix list once the, motor is back together. Its not something I've heard of much here but I guess it would only be divers who would see this?

Will let you all know how we get on.
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Old 10 June 2007, 20:59   #18
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Its not something I've heard of much here but I guess it would only be divers who would see this?
No, I think divers (or most divers, anyway) tend to run fairly high speed most of the time. Not much time spent idling along except when looking for structure to dive on. Most of the running is point A to point B fast stuff.

The problem is more prevalent among blue-water fishermen and lake trollers. Those guys run high rpms to get to their fishing grounds, then idle along trolling for hours at a time.

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Old 29 June 2007, 09:18   #19
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Oil analysis back from Caterpillar in Leeds; some water but a lot more fuel so it looks like we were "making oil" in some form. We'll monitor and then see if it re-occurs, if it does then we'll have to work down the list of known fixes from US will keep posting results.

This is the first time we have seen this and the only thing different in how we used the engine was allowing it to run on tick over (not in gear) for about 3 hours to charge the flat battery.
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Old 18 February 2008, 10:28   #20
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Postscript

Just had the motor back from it's annual service, thermostat was jammed in open, thus engine has been running cool all year (or part of) Will see why it's jammed in a bit.
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