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Old 24 January 2005, 07:55   #21
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Country: UK - England
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Boat name: JU-JU
Make: Halmatic PAC22
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Quote:
Originally Posted by Bilge Rat
Sorry if this sounds really nieve but can someone explain why fitting an additional fuel/water seperator filter in addition to the standard small one supplied in the engine would be a bad thing...........
Each filter in the line will result in a pressure/ flow drop and because your water separator is on the vacuum side of the system it is even more critical. Potentially you could get fuel starvation at WOT and if nothing else it will put more strain on the system.

Cars get around this by putting the pump in the tank and pumping more fuel around the system than is needed so all the filters are pressure fed. Des
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Old 24 January 2005, 13:03   #22
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Country: Ireland
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Boat name: XS-600
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Engine: Merc Optimax 150 XL
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I've got a transom mount fuel filter fitted to my Opti 150. Barnet Marine fit them as standard, as do my local Mercury dealer and I've never heard of any problems from either of them. I use a Racor water/fuel separator, which I understand to be one of the best available. Never had any trouble.

Des as you say it is quite possible to get a pressure drop/fuel starvation problem. From talking to a Barrus engineer he said that as long as I was using a good quality filter and cleaning it regularly there shouldn't be a problem. Also he commented that most fuel filter fuel starvation problems occur as a result of the height of the fuel tank relative to the engine, so I would imagine this is more prone with underdeck fuel tanks than console mounted tanks.
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Old 24 January 2005, 13:18   #23
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Country: UK - England
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Make: Pacific 22
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filters

Quote:
Originally Posted by CJL
Sorry Paul but if you look in the manual for an OPTIMAX it clearly says you shouldn't fit one.

That said I`ve got one on a boat I bought recently and no problems. But I'd read your manual take on board the advice from Merc then decide before I did ANYTHING.


Chris
When i had a problem with an opti i was recommended by Mercury to fit it to all optis and four stroke EFIs
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Old 24 January 2005, 14:24   #24
CND
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There are ultimately going to be a number of factors effecting the pressure in the tank, the height of the tank (bearing in mind this is a RIB, steady object), such as the effectiveness of the breather on the tank, the ambient air temperature and the length of your fuel line.

As the optimax's are so sensitive to the amount of fuel available it seems entirely reasonable, from what we have discussed here, that if you have got a fuel filter on your transom then if you are pottering up a river for a bit then it might just die on you, due to fuel starvation.

Not an uncommon problem in the marine world?

Obvioulsy running out at sea there is not going to be a massive problem, with possibly a slight dip in top end performance. Blatantly the better fuel you put in and the more of it the more complete combustion you will get, but, with such a sensitive system on optimax's...what can happen? will it get a bit upset electronically?

anybody got any stories to share on what can go wrong?
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Old 24 January 2005, 17:25   #25
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Opti fuel

Had an opti in the other day (115) straight from warrior boats and that had a water sep mounted, however not the best one around as it had the old glass bowl on it,wont be much good if it gets hit by something.
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