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Mercury 120 diesel oil extraction

Printed From: The Solent Fishing Forums
Category: Fishing Forums
Forum Name: Boat Talk
Forum Description: This forum is for anything related to local boat fishing
Printed Date: 19 October 2019 at 9:32pm

Topic: Mercury 120 diesel oil extraction
Subject: Mercury 120 diesel oil extraction
Date Posted: 14 December 2015 at 12:26pm
Hi guys, anyone have any experience here with a 2004 (ish) mercury 120 diesel (its the 1.7td isuzu as used in vauxhall astras etc)
Its in a friends boat and he cant get the oil out of it, following the mercury manual, connecting suction pump to dipstick tube he can only extract 2lt of approx 5lt total capacity.
Following the normal procedure for most inboards i come across of poking your peli extractor tube down the dipstick tube he can also only extract 2lt.
Tried feeding the tube down bit by bit, extracting bit by bit etc so an not to go too far/curl up in sump etc, still exactly the same only 2lts will come out.
For the record, the oil is hot and the level indicated normal/full on dipstick before we started
The dipstick tube looks original and unmolested and connects to starboard side of sump at bottom middle area. The fitting on the sump has a connection also for the breather catch tank return, also all looks standard/original
I know it sounds like there is a couple of chimps in overalls dancing on an engine box right now, but in 16 years of working on inboard diesels ive never come across this before (this is the first mercury 120 ive worked on though)
Granted they can be tricky sometimes and take some fine adjustment of the extractor tube to get everything out, but only 2lts is so far short of the mark i am baffled

Posted By: Essgee
Date Posted: 14 December 2015 at 8:34pm
Probably stating the obvious but have you checked that the length of tube that is going in equals the distance to the bottom of the sump. Seems like you are not getting to bottom of it 😀😀😀


Date Posted: 14 December 2015 at 8:53pm
yeah its reaching the bottom, but tbh it shouldn't matter if its sealed to the dipstick tube, the mercury manual states the procedure is just suck directly out the top of the dipstick tube.
Both methods produce he same result, even the mercruiser dealer i spoke to is baffledConfused

Posted By: Essgee
Date Posted: 14 December 2015 at 11:00pm
Sorry for my ignorance, was aware you sucked the oil out of marine diesels but hadn't given much thought to how. Based on what you've said is it conceivable that the dipstick tube has got a whole/ split in it part way down meaning it sucks air when the oil drops to that level. Wouldn't explain why a tube pushed to the bottom doesn't work though.


Date Posted: 14 December 2015 at 11:38pm
Yeah my first thought was air getting in at a certain level, but then i would have an oil leak at full level and the bilge is clean as a whistle.
Then there is the breather catch tank return pipe that ties in at the sump fitting, so i blocked that and still no joy. 
Then came the tube right to the bottom, same result
Next job is try and alter the angle of the boat drastically towards the sump connection i think, see if that makes a difference

Posted By: hightower
Date Posted: 15 December 2015 at 6:48pm
Perhaps the sump is specially shaped to allow the pump pickup to be in a lower position to that of where the dipstick goes. This acts like a kind of baffle, keeping the pump or strainer submerged in oil. So perhaps the tube isn't going to the very bottom of the sump and is sitting on the raised shelf?


Date Posted: 15 December 2015 at 7:04pm
Looked into that. Found a schematic and the dipstick tube goes in at the bottom of the sump.
I'm going to try another method in next few days and will report back

Posted By: Essgee
Date Posted: 15 December 2015 at 7:50pm
So once you've got your 2 litres out can you poke a stiff wire down the dipstick hole, right to the bottom, and if so does it show a depth of oil left. If not it's either empty or you didn't get to the bottom.


Posted By: billy the fish
Date Posted: 16 December 2015 at 7:46pm
take of the oil filter and push a bit of hose on the nipple and stick the other end in a 20ltr plastic can, start the engine and pump it straight into the drum for the few seconds it takes the to pump it out of the sump should not harm the motor do not seal the pipe in the 20ltr can leave plenty of air space around it else you will look like the ting that used to be on the marmalade jars Wink also make sure its the right outlet if in doubt use 2 tubes Wink

if you have to measure it, its too small!!

Posted By: Doombar Dave
Date Posted: 16 December 2015 at 10:28pm
What will make your hair go curly, Oh golly thats not good

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