60 hp EFI Loses Power and Runs Rough

[WICKER55]

After a $1000 bill from the marina my motor still runs the same As before I took it in. The engine start great, idles great and takes off like it should to get on plane. Once on plane the rpm’s rise to full power of 5800 at WOT then starts to noticeably reduce rpm’s and running rough with the throttle control still at full throttle. The marginal said they found the problem and replaced a bad coil but the problem has not gone away. By the time I got the boat bake to the dock it was misfiring badly. I can’t afford to send it back to the marina. Does anyone have any suggestions what I might try?

 

[WICKER55]

After a $1000 bill from the marina my motor still runs the same As before I took it in. The engine start great, idles great and takes off like it should to get on plane. Once on plane the rpm’s rise to full power of 5800 at WOT then starts to noticeably reduce rpm’s and running rough with the throttle control still at full throttle. The marginal said they found the problem and replaced a bad coil but the problem has not gone away. By the time I got the boat bake to the dock it was misfiring badly. I can’t afford to send it back to the marina. Does anyone have any suggestions what I might try?

 

[racerone]

Is this a 2 hp or 400 hp motor.----Why not tell the good folks here.

 

[stresspoint]

you paid $1000 bucks for a coil !.

can we have some info on what motor your boat has yo better give you help on where to start looking.

 

[Cortes100]

The most logical thing to do is take it back to the marina?? You paid them $1000 for a problem they didn't fix.

 

[WICKER55]

So sorry, it’s A 2007 Mercury 60 hp EFI on a 16 ft Legend Xcalibur.

 

[QBhoy]

Hi. Tell us what they said they all checked or looked at for the money. Just to maybe try rule things out. Although sounds like they aren’t too great anyway.
I’d check the fuel system over in more depth. Assuming filters and fuel is good to start with…I’d be going straight to the VST. Check if there is a strainer in there or crap needing cleaned out. Perhaps the pump is struggling in there as a result. Or something similar.

 

[WICKER55]

Marina found no faults on computer diagnostics. Said it was running fine on earmuffs. Problems only occur under load at WOT. They said they took it for a test in the lake and found coil on number 4 cylinder was bad. They replaced coil and said problem should be solved. I took it out for the first time following getting the boat back, same problem as before. So far this has been done.
-all fuel lines replaced from the tank to the engine including fuel pickup tube , anti siphon valve and half ball pump.
- both fuel filters
- low pressure fuel pump
- VST tank cleaned and high pressure pump replaced
-all coil packs have been replaced
-spark plug wires replaced.