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Old 20 October 2013, 17:27   #1
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Optimax 225, 2004 surging at high revs

I'm hoping theres an optimax guru that can help me. Above 4000 rpm the boat seems fuel starved and is surging, throttle off and it runs fine and at cruising speed runs like a top. This has happened since a few bumpy trips and the water seperator was full of black spots, probably degraded fuel pipe and some browny, sh))y fluid

Heres what I'm planning. Am I on the right track?

Replace all fuel pipes, right up to fuel pump.
Replace water separator
Replace fuel filter

Question - is that the right thing to do or should I to straight to putting a pressure gauge on the low pressure pump and/or strip that down first.

Thanks
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Old 20 October 2013, 18:01   #2
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There should be.10psi deference on a fuel an airside 80 to 90psi off the top of my head
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Old 22 October 2013, 15:19   #3
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Put a fuel pressure and air pressure gauge on it. Without that it could be all sorts. Although it sounds like the low pressure (lift pump) to me.
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Old 22 October 2013, 15:39   #4
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Quote:
Originally Posted by Turbodiesel View Post
Although it sounds like the low pressure (lift pump) to me.
Yep that's what mine was! Check the current draw to the pump, it's listed in the manual, if it's high it's knackered. You should also be able to feel it cycle when key is turned on....
Mine decided to fail just before we were due to leave for the SOF. Turbodiesel sent the new part overnight and saved the holiday!

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Old 22 October 2013, 16:56   #5
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Thanks guys. I've decided to replace all fuel hoses, bulb, water seperator, vst filter and low pressure pump diaphragms. May sounds over kill but I hate fuel supply issues. I'm also going to do the plugs just in case. If it turns out not to fix it I will get a friendly dealer to check the rail pressures.
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Old 23 October 2013, 04:32   #6
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There's 3 fuel pumps on the opti: vacuum on the block and the two electric ones in the vapour separator on the port side of the engine.
If the low pressure electric one fails the vacuum pump will just about keep up with suppling the chamber that feeds the HP pump. As soon as the fuel demand increases the pressure drops off and you get the big misfires/poor running you describe. It's a really easy check, just check the current draw. If it's pulling more than a couple of amps it's probably US.....that's the process I used to find the fault on mine and as described in the w/shop manual. since fitting the new pump a she's been running great! (Nearly 100hrs added this year)
Good luck....

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Old 28 October 2013, 03:15   #7
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As described earlier, all pipes, filters and plugs replaced. Low pressure pump kit put in and new plugs and it ran perfectly. Challenge this weekend was finding smooth water to get to wot!
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Old 05 November 2013, 09:14   #8
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Mind that the low pressure pump membrames have to be replaced everey 300h service!
We ususally did them yearly with frequently used Opti's.
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Old 05 November 2013, 11:46   #9
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Mind that the low pressure pump membrames have to be replaced everey 300h service! We ususally did them yearly with frequently used Opti's.
The vacuum pump ones?
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Old 05 November 2013, 13:02   #10
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That's interesting. There's less than 200 hours on the engine but the rubbers were pretty nasty, virtually lost all elasticity. For the cost I will probably replace annually.
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