re-calibrated or another issue ?

S

Strrykerr

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I recently re-powered and installed new 350 vortex long blocks rated at 310 hp, replacing tried 350 merc mags rated at 300 hp. I ran the engines for 20 hrs not going over 2500 rpm for break in period. The engines ran fine no issues however I am unable to get over 3000 rpms and it feels as if the engines are flooding out -------- that is when I raise the throttles the engines will not go over 3000 rpms however there is ample room to forward the throttles however the engines still remain at 3000. When the engines are not under load they easily reach 4800 prm. Do the engines need to be re-calibrated ?
 
how did you set the timing?? are you certain you have good fuel flow?
 
When was the last time you checked your props. That is exactly the symptoms my boat exhibits when the props need cleaning.

George
 
That sounds like a long time to keep it under 2500:

http://www.boatered.com/forum/topic.asp?TOPIC_ID=51384

http://www.perfprotech.com/store/articles/merc-breakin.aspx

That's an MPI? Have you had it scanned to check for parameters out of spec , at least check for codes tripped? Could the RPMs be limited by the ECM due to knock-sensor feedback?

Does it stll run smoothly at 3000 as you increase throttle, or is there bucking/coughing?

You have new fuel pumps & regulator on that long block right? Check fuel pressure? FloScan won't tell you if pressure is too low to go to higher RPMs.
(FWIW-Don't know for Merc, but my 350ci /330hp Crusader MPI's spec " 57-62 psi at WOT for systems with return lines and 57-0psi ar WOT for the retunrless system I have. The LPFP specs 4-7 psi at WOT. All figures are with engine under load." )

Any chance there is an exhaust restriction? Any chance the throttle cable is slipping?
The ignition is back in Run mode , not still on Time mode , yes? (Sorry, just asking.)

Are you still using the same reduction gear ratio and prop?
 
Bruce --- will recheck firing order this weekend
George --- hull repainted and props re-certified computer balanced
Sandy ---- Yes its a MPI
not scanned (unsure how to proceed with that)
unsure how to determine limited RPMs by ECM due to knock-sensor feedback
Will check for codes tripped this weekend
runs perfect until 3000 very smooth
new fuel pumps / cooler / regulator / new injectors /rebuilt water pumps / new ignition coils
same reduction gear & props

This is my 3rd re-power no issues until now ---- just a long shot previous re-powers were with 300 hp vortex and
these new vortex units are rated at 310 hp carberated ?

GP

no exhaust restriction --already checked same with throttle cable
 
are there two engines doing the exact same thing?

are you certain the props are clean?? It doesent take long for stuff to grow.
 
Props and hull were cleaned last week, here in the pacific northwest growth is slow compared to warmer waters.
 
Strange as it sounds thats Mercs Rpm limit point if a sensor throws a code when an engine is running in safe mode. The other thing that comes to mind is are you over propped? What type of drives straight of V drives? I do realize you have been through this before so over prop doesn't sound like it could be your problem. What happens when you rev the motors past 3000 in idle does the warning beeper go off? When you say recalibrate what the ECM's? Do the motors even have ECM's?
You might have one motor with a problem not allowing the other to reach WOT.
Bill
 
If one was the problem their max rpm would not be equal unless he has the synch on.
 
Bill --- Not over propped --running Albemarle 28 straight drives
when not under load in idle motors run up to red line with ease --no warning beeper
my guess was to recalibrate both ECMs ---a shot in the dark as I'm reaching here
Bruce --- no synch on board.

as you can see I'm at a loss on this one
 
did you use all the old elcetronics and fuel system?
 
Ok let me get this straight you have no engine sync, so Bruce I could be right about one engine causing the problem. The ECM's would definately need to be recalibrated in my opinion. Is the ignition timing controlled by the ECM's?
 
Bill: In my experience the engines would have different RPMs and the extra thrust by the strong engine would be obvious.
 
Bruce is your experience based on diesels? On my underpowered gasser if I get a weak engine because I am in limp mode on one I can't get the boat on plane and hence the rpms stay pretty much stable or static on both engines at 3200 rpm.
Now perhaps because I have SmartCraft and engine syncs this has been my experience. Even when I have dropped the sync out I had the same results. However my engines are MPI and fully electronic controlled.
Bill
 
Bill - With a pair of MPI engines that have a twin-engine harness (just 2 wires as I semi-recall) installed between them , if one engine's ECM senses a condition which requires dropping to Limp Mode RPM's , the other ECM will immediately do the same so steering remains controllable & one engine is not left with an inordinate load . If no twin -engine harness, the other will not drop RPM's . That RPM safety feature is independent of sync function. I added that cable to my Crusaders.
 
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