Need help2015 merc 60 40 four stroke jet with 56 hours.

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mark2052

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Need help. The motor will not go beyond 4,600 rpm. Gradual decline in rpm out put over four week period from 5,500 to 4,600 rpm. Dealer found no codes. replaced plugs, impeller with new wear ring, fuel filters ect . 1k spent still have same problem. Called Mercury no help whatsoever. Compression good 145 per cylinder. Motor runs fine no misses, skips, or hesitation. The dealer wants to replace fuel injectors with no guarantee parts replacement will fix problem. Need opinions or suggestions. Please help. Thanks in advance Mark.
 
Sounds like fuel starvation to me. Fuel injectors at 56 hours? Doesn't seem likely to me. However, I'm not a mechanic. I would check for a blocked fuel filter if it has one. Perhaps the fuel tank is starving for air? That's all I can offer to look for. Maybe a different dealer is best but more money is spent.
 
mark2052 said:
Dealer found no codes. replaced plugs, impeller with new wear ring, fuel filters ect . 1k spent
Click to expand...

What? $1K, that's crazy.

Anyway it definitely sounds like a fuel issue (so not sure why they replaced the plugs). I only works on carbs, but not sure why they go right to replacing injectors, but I'd think they can be cleaned for much less.
I would think that the decoder should be able to read live data.
 
MDCrappie said:
What? $1K, that's crazy.

Anyway it definitely sounds like a fuel issue (so not sure why they replaced the plugs). I only works on carbs, but not sure why they go right to replacing injectors, but I'd think they can be cleaned for much less.
I would think that the decoder should be able to read live data.
Click to expand...
Humm... interesting.. .well decoders might be able to detect FAILURES pretty good but if nothing is failed.. and with good compression, idle, ect.. don't sound like anything FAILED.. sure sounds like fuel issue.. ? stupid ? does the primer bulb stay hard.. is the tank vent ok ,
might be a cheap diag to run a small aux gas tank/hoze/bulb..
 
The low hours for the age of the motor may indicate it sat for a while. The gas may have gummed up some part of the fuel system.
 
Sea Antsy said:
Humm... interesting.. .well decoders might be able to detect FAILURES pretty good but if nothing is failed.. and with good compression, idle, ect.. don't sound like anything FAILED.. sure sounds like fuel issue.. ? stupid ? does the primer bulb stay hard.. is the tank vent ok ,
might be a cheap diag to run a small aux gas tank/hoze/bulb..
Click to expand...

The word I was looking for was analyzer, not decoder (or cheap scan tool). Most engine analyzers (on cars at least) give you reading from all the sensors while the engine is running. Fuel, pressures, throttle position, timing, exhaust mixtures, etc. Haven't been to a marine repair shop in over 20 years, but figured they were on the same level as auto shops now, right? Maybe not, but I figured outboard are at least as advanced, probably even more so then autos now.
 
FuzzyGrub said:
The low hours for the age of the motor may indicate it sat for a while. The gas may have gummed up some part of the fuel system.
Click to expand...
You're probably correct. Old fuel that's gummed up from age. If the motor is running, I'd drain the existing gas and start with high octane fresh fuel and maybe even a fuel additive to clean things up. Even if this isn't the direct cause, it should be done at any rate.
 
Did you change out the tank to motor fuel line? The ones with liners tend to collapse and starve the motor of fuel.
That's what happened to my 2013 60/40.
 
Call an injector shop to see if they can clean the injectors. Also try a different tank and fuel line.

What liner did they replace? The impeller liner or the jet pump liner? Are you greasing the bearing on the jet pump after every use?
 
Put a fuel pressure gauge on it and go for a ride. See if fuel pressure drops or stays steady at speed. Will tell you if the problem is in the pumps or supply side, or in the motor itself. That should have a schrader port on the fuel rail that will work with any automotive style fuel pressure gauge.

If the fuel pressure is good and you still suspect a fuel problem, a lot of automotive performance shops have the equipment to flow test and clean fuel injectors.
 

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