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Old 06 August 2009, 12:28   #1
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Power loss .....

A potential puzzle for anyone technical / mechanical

Ran up to Newtown harbour for abit of lunch today - on the way back at 35-40knts and the engine started loosing power (about 4000 rpm) - not misfiring by the sound of it , just not putting power out . Nothing round the prop, or leg & no warings from the gauges - temp/ pressure / volts etc etc all normal . More throttle = less power & throttle back & it runs fine .

Was worried it may be a call for a tow , but made it back fine (just slower). Merc dealer thinks its a fuel supply prob - so new filter / bulb / pipes etc fited in the rain - checked tank - pickup OK . ( I seem to have bust the fuel sender as a seperate issue - typical ! ) .

Oil is fine - defo not guardian mode

Tank full of nice new petrol - tank not cracked/ empty etc.

Any thoughts or suggestions ?

Have to wait till Sat or Sun to test - so listen out for my call for help when it stops completely

Pete
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Old 06 August 2009, 12:45   #2
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Seems to be fuel problem. Dirty gasoline and cloged up carb or not enough pressure to supply enough at high RPM.
Try and test method should solve this nuissance.
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Old 06 August 2009, 12:49   #3
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A good starting point - probably pulling 35-50 LPH at the speeds it happened. No carbs to worry about on the opti & clean fresh gas ( it looked & tasted ok ! and only filled it last week. )

Just wondering if those in the know agree with the diagnosis, and anyont got a new sender I can stick in it !
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Old 06 August 2009, 18:34   #4
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Had very similar on my opti 225 recently. throttled back an all fine - to me it felt like a fuel issue. Looked into it and found a slightly flatened fuel line where i had re-rigged it out of the engine (the angle was too acute). straightened it out, cut out the compressed bit and all back to normal. it was simple fuel starvation - the pump could not draw enough.
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Old 06 August 2009, 18:51   #5
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Is there a fuel filter under the engine cover, I'm guessing there is. Has this been replaced?
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Old 07 August 2009, 04:31   #6
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Quote:
Originally Posted by Hightower View Post
Is there a fuel filter under the engine cover, I'm guessing there is. Has this been replaced?
Good question ! If there is I would hope it was changed at its last service in November 08. The main filter/ seperator had a few 'bits' in it , no sign of any water in it or the tank & the bits I dont think were enought to reduce the flow significantly.

Merc dealer didn't even take the hood off - just concerned with tank /main filter.

From what has been said I''l pray its as simple as restrcited flow fro some reason.

Pete
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Old 07 August 2009, 05:12   #7
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This is all very interesting as this is EXACTLY the same issue I'm having on my Suzi Dt55 (see my other thread if interested!)

Yesterday she ran great - then on way back the engine dropped off to 4200rpm and would rev anymore - more throttle - nothing.
We just eased off throttle and she sat at 4200rpm happily - she cruised home not missing a beat - took over 10mins.
I have new fresh petrol and had only changed the fuel lines and filter at start of season - also added a water/fuel separator filter.

This sounds basically the same problem as Blackroady's - I've been plagued with it all season. Why would the engine run ok for a while then suddenly loose power if it's fuel issue??
Is the fuel pump serviceable??
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Old 07 August 2009, 05:15   #8
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Quote:
Originally Posted by Blackroady View Post
A potential puzzle for anyone technical / mechanical

Ran up to Newtown harbour for abit of lunch today - on the way back at 35-40knts and the engine started loosing power (about 4000 rpm) - not misfiring by the sound of it , just not putting power out . Nothing round the prop, or leg & no warings from the gauges - temp/ pressure / volts etc etc all normal . More throttle = less power & throttle back & it runs fine .

Was worried it may be a call for a tow , but made it back fine (just slower). Merc dealer thinks its a fuel supply prob - so new filter / bulb / pipes etc fited in the rain - checked tank - pickup OK . ( I seem to have bust the fuel sender as a seperate issue - typical ! ) .

Oil is fine - defo not guardian mode

Tank full of nice new petrol - tank not cracked/ empty etc.

Any thoughts or suggestions ?

Have to wait till Sat or Sun to test - so listen out for my call for help when it stops completely

Pete



Pete, meant to ask - Did this happen after a service or after you doing any work on the boat OR was it out of the blue?
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Old 07 August 2009, 05:26   #9
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Was totally out of the blue - has been running without fault all year. Nothing changed or tinkered with to cause it. ( Apart form of course the never ending pounding that outboards get on a RIB ! ) I am wondering if it could be something as simple as the primer bulb collapsing & not letting the petrol though.

For me it was all round the rev rev range from 3500 upwards - it might rev to 5k , then drop back , or it might rev to 4200 then drop back , or 5500 then drop off - so not set limit - which seems a little differant to your fixed rev problem.

Like you - no warnings on the guages ( and the smartcraft ones seem to have a warning for everything ! )

Is it possible that there is dodgy petrol around ? Or do all our motors have a sensor that has happened to play up at the same time - but both these would be slim odds given the location of where we buy petrol & you are Suz & me an Opti ............
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Old 07 August 2009, 06:58   #10
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I had a mysterious drop of 400rpm on my 150 opti. Thought it was a fuel problem and spent a fortune chasing the problem. Turned out to be an HT lead breaking down.

About 60 to change.
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