Magic 260,Magically loses power!

[2scoops]

Chasing errant problem since last year,97 260 running great,Rpm,s 8000 plus Egt at 950 degrees,make a turn to head back the other direction and half way thru the turn I can feel the thing just lay on it,s face!Heading back the other way Rpm,s at 6800 and egt buried at 600 degrees!Fuel pressure good at 50Lbs,Battery at 12.65 volts,Fresh plugs and fuel filters.Starts idles and runs fine,Doesnt make any noise.Last time it corrected itself,I was running along with no exhaust temp praying to god a strong running Bayliner didnt pass me,when snap, rpm and exhaust temp magically return!I have got to find a definitive problem,I thought it was fixed!!!!

[patchesII]

check all your grounds and especially your coils. i would think that if you lost spark on a cylinder or two it would do this.

[stvhelm]

Trigger. Mine was bad when something similar happened. it ran fine for a few miutes after it cooled. then when it got warmed up it would drop cylinders. problem came and went without warning. usually happened after about 5 minutes running from when I first would start it. it was a real pain. it took me a long time to figure it out.

[Brad Zastrow]

Just a thought...but you mentioned it happens when you are turning. The loss of power and low egt temp is a classic starving for fuel symptom. Have you considered that your gas pickup tube is losing the fuel sloshing around? Or maybe plugged? Also why are you running 50 lbs and not more like 35? Is it a drag boat?

[Raceman]

When one of mine laid down the driver in the ECU wasn't firing the injectors on the top 2 cyl's, so it was a V4. I doubt that an ECU problem would be intermittent though unless there's a ground issue. If it were temporary fuel starvation you should see a fluctuation and it should be momentary, rather than an extended time. Helmut's trigger suggestion sounds reasonable to me.

Are you running the right regulator for your ECU?

[2scoops]

Thanks for the input guys,There is no where to turn for help on these things around here!I am going to check all the grounds first,I think it has something to do with the lower two cylinders,I just changed the plugs(BUZHW)all looked good except the lower two which looked black and sooty.Raceman it does feel like it turns into a V4,but it has done this on several occasions and always reverts back,did yours also do this then change back?Brad it doesnt always do it when I change direction,It just happened that way this time!The 50LB fuel pressure is normal,Mods done by previos owner,and has run perfect in past seasons,I havent had a chance to throw a wrench at it,Hopefully tomorrow.I think it,s definately a spark problem causing the lower two cylinders to drop intermittently,Any tests I can perform on the components you guys have mentioned I would appreciate,Keep the good ideas coming!

[Fl Boy in ILL]

We just had a coil problem on our 260, check ground first though. We actually had some hidden cracking on the coils, good luck.

Rick

[stvhelm]

Rick, can you describe the symptoms you had with the broken coils in detail? the end of last year I changed all my coils cause the magnets were all busted and I magically lost 200 rpms. I changed them all again and no difference. Im ready to break all the magnets again and run it. the problem i was chasing turned out to be a bad trigger but, Im still not sure what happened. the original problem was it would drop a cylinder after a few minutes of use. it runs fine now but I still feel im down about 200 r's

[sosmerc]

I would hook up a DVA meter to a remote selector switch so that you can quickly test the input voltage to all coils with the flip of a switch. Merc makes this tool with an extension harness so you can do this while driving. You have all six coils hooked up to the selector. Or you can move the leads to the whatever you want to check such as trigger leads, or stator output leads. This is very helpful when chasing an intermittant spark problem. Remember also, if you are loosing input voltage on either 1, 3, or 5 you are also going to loose fuel to 2 injectors because the injectors are fired in pairs from the switchbox output voltage on 1, 3, and 5.

[Hydroballistic]

Had one I chased for several weeks last summer that turned out to be the ECU. I was suspecting the ignition, but turned out to be the ECU. Customer said it would make a pass or two running great then would loose power. I took it to the lake twice and it ran fine both times, thought the customer was crazy, but finally got it to act up for us in the test cell one day. ECU would just quit firing two of the injectors then at some point would start firing the injectors again. The unit that this one was on was a 260 with digital box, no TPI, and the internal part of the box is not totally submerged in epoxy. Learned from Rapair that this is not too uncommon on these units.

Try another ECU if you can to rule it out.

Gregg

[2scoops]

Cleaned the grounds,looked like the lower coil connections could have been the problem but werent.I will move on to the trigger and the ECU,I am calling sosmerc for help tonight,Can I send the ECU out to be tested?Where can I go (mail order)to buy this stuff,I cant deal with my local no performance dealer!

[Unloaded Racing]

Sounds like the same problem I had this last weekend. Make one pass and would run fine, next pass at about half track would start loosing RPM. Changed stator, trigger, and both switch boxes. Problem was still there. Checked coils and they checked good. Changed ECU's and as magically as the problem appeared it was fixed. You can send your ECU to Rapair and they will fix it. Mine is there now. Hope this helps.

Tim

[Techno]

After the merc dealer told me he couldn't help on parts and his "mechanic" of 20 years experience had no idea where to start. (it would have been a hunt search at xx $ per hour!) All this because the merc was a mercenstien 2.4 and had no book for it, and it was HI PO and he didn't work on them or have anything to do with them.
I found an RV place somewhat nearby that had merc certified mechanics who weren't afraid to work on it.
Stuck a tester, replaced the stator and that problem was fixed.

Needed Head gaskets and found another merc shop that can work on my engine.
They may be hard to find but you still might be in luck and have a shop 'nearby' that can do the work on it that would otherwise be parts changing.

[Markus]

Did you solve it?

[2scoops]

Magic 260 is back to it,s former glory!I switched ecu,s to a known good one and that wasnt it,I then changed the switch boxs and at the same time found some corrosion on the pins on the lowest fuel injector.I did both things at the same time so I dont know which was the problem but it runs great now.My guess is that it was the corrosion on the fuel injector connection because of it,s intermittent status.A good mechanic is a lazy mechanic and checks all the easy and free things first.I,m just glad it,s fixed now!Thanks to all that helped and a special thanks to:Rothwell marine,Simon motorsports,Rapair,and Tony Brucato