Loss of power at wot, Merc 250 ProXS

This topic has 9 replies, 4 voices, and was last updated 13 years, 11 months ago by Kirk Simpson.

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June 30, 2012 at 12:20 am #358603

Kirk Simpson
Participant

While running at wot or close to it, occasionally been loosing power as if its going into an overspeed mode. Tach will read 5600-5700ish, def not nearing 6000rpms, speeds near or at 70ish. I have a 26Fury on a 08Puma. All of a suddon it will just feels like Im taking my foot off the pedal and its coasting down to around 50mph. Mercury said the alarm bell for overrev is loud and easy to hear, and the rev limiter is set to engage at 5950rpms. Im not hearing any alarm bells. The temp on the SC gauge reads 123 or so and its squirting water out just fine.Were right in the middle of our tournament season here in Michigan, hate to have it sit in some mechanic shop for 2 weeks before they look at it. Any help in diagnosing what could cause this is sure appreciated.

June 30, 2012 at 12:52 am #358607

Bass Cat Boats
Keymaster

2008 is pre-ethanol fuel lines. Not sure if thats an issue, though check the line to engine.

June 30, 2012 at 2:55 am #358611

Bass Cat Boats
Keymaster

Am I checking the lines for hardness, cracks, etc??? What should I be looking for? Wouldnt it do it all the time if it were a fuel line issue? The boat was brand new in 2010, Im the orig owner, and have always used Startron fuel treatments and 93 octane fuel.

June 30, 2012 at 3:16 am #358614

Bass Cat Boats
Keymaster

We believe BLUE lettering and Ethanol Resistant labeling on the engine hose from the fuel valve. RED lettering on the grey hose we think is the old hose.

June 30, 2012 at 7:35 pm #358617

jpace
Participant

It might be deflection in the plate that holds the map sensor. Does it stedily lose speed on longer runs?

June 30, 2012 at 9:49 pm #358620

dbasketman
Participant

Check the coils, sounds like one going bad. They can go in two ways, one is out, other under a load.

July 2, 2012 at 1:55 pm #358623

Kirk Simpson
Participant

The grey fuel line has red lettering on it. Im not sure how to check the map sensor and the coil.

July 2, 2012 at 1:56 pm #358626

Bass Cat Boats
Keymaster

Part of the problem is that it doesnt do this all of the time. Makes diagnosing it a real pain.

July 3, 2012 at 3:28 am #358629

Bass Cat Boats
Keymaster

We lean to ECM.

July 5, 2012 at 5:10 pm #358631

Kirk Simpson
Participant

Ok, I replaced the grey fuel line that had the red lettering, and put on the grey with the blue lettering. That seems to have solved the problem, in fact, the Cat is running like a scalded dog. When I cut open the fuel line, you could see the laminated liner that is supposed to be glued to the inner wall had come free and collapsed and was restricting the fuel flow as the engine was demanding more fuel at higher speeds. Hope this solves it. All else seems to be running great!
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