LK 525sc382

I have a pair of 2011 Merc 700 sc motors. Won't go over 4000 rpms. Runs and starts fine up to that rpm. I changed the fuel filter but, it didn't change. Any thoughts or ideas out there. THANKS LK

xwing

what does the smartcraft monitor say?
Any alarms/warnings?
Under what conditions, out of water, in water driving? What boat speed? what is water pressure etc?
2 engines not going over 4k, not just one, is weird.

RT930turbo

What kind of boat? Does it sit in the water? Is this a new development all of a sudden? Props correct?

whirlwind

I am having the same problem with the port motor. No alarms or codes on Smart Craft. And there is a miss at rpm above 3000

klalonde

Try turning off batteries, wait for a few minutes this can reset the ecu. Had this happen on my boat corrected the issue.

xwing

look at the boost pressure of the superchargers.
Stock programming has no boost (~1psi max) until ~3000 rpm; then the computer closes the supercharger's wastegate to allow max of about 7psi boost (yes it is not a turbo but has a boost diverter to control boost).

I wonder if your wastegates are somehow stuck open, and it is never developing boost, but the computer is giving it gas as though it has boost so running super rich and possibly into area of fuel mapping that is not really laid out, as it never should see that throttle with that rpm and no boost.
At 4000rpm full throttle, you should be hard on boost at 5-7psi, no matter what HP being made, as the superchargers don't count on exhaust heat/volume but are pure (engine speed vs demand) related.
I don't know the algorithms Mercury uses on their computers, but one of the Merc Computer Reprogramming Gurus on this board could probably tell you what the problem is.

If it was low fuel pressure it would throw codes and buzzers; likewise if put into Guardian mode due to low oil or water pressure, I believe it would yell at you too.

Make sure your battery is good and voltage 12-14v running, if the voltage drops the computer and ignition can get funky and less resistant to EMF interference too.
Make sure your airfilters are clean.
check your plugs, see if one or a few are fouled out; change plugs.
If an injector wasn't hooked up I would think it would throw a code, but on 2 engines at once, that's unlikely.

Were the engines ever worked on/rebuilt in any way?
When did they last run JUST FINE, and were YOU owner/driver when they last ran JUST FINE?

Randy Nielsen

iTrader: (4)

This may not apply in your situation but I have seen it where trying to rev the engines with no load the ecu will shut them down at 3-4000 rpm so they won't over rev. Just throwing a suggestion out there. Randy

LK 525sc382

I had a Merc Tech check motors with his computer and there are NO faults. The boat runs fine up to 4000rpm. Oil pressure. water pressure, temps, volts meters, and boost pressure are good. Shows 8 lbs boost but still won't go over 4000 rpm which is 70mph, the boat will do 90 mph at 5100 rpm. ????

wellcrafted

Not sure if this helps, but my 2009 600 sci , had number 7 & 8 coils were bad, showed okay under cold test everything was fine , ran them under a load and both were bad , replaced them all is good.,

cdowns

I would bet money it's the coil packs. Had the same issue twice.