1 Hr. on 2000/2.5 280, please send tissues

[David Johns]

Hi fellow Scream and Flyers.

I just completed a $1500 dollars rebuild on my 2.5. Last September I stuck a#5 piston and send the block out to Ruck Machine, pistons out to Marles. Replaced reeds etc. I returned the injectors to Brucato for evaluation and service. "Clean bill of health". I serviced the cooling system and left it at that. I Had a chance yesterday to put some break-in time on the engine. I cycled the engine, gently for about 1 hour and at 6000rpm the motor seized again. I removed the heads and found a severely melted#5, again. Questions??? What is going on here? All 6 spark plugs look lean. Could my ECU or sensors be messed up? Could I have fuel restriction? Could 2-3 month old gas do this? I Fried at 6000 the first time too. I'm very sad. Paid $10000 for a 50 hr. motor. Already Put $1500 in plus roughly $1000 for this. All for 25 hrs. of fun??? Does anyone have any thoughts or ideas?
Thanks in advance. :( Dave

[Ospreyproduction]

Dave,
Hate to hear about the trouble. I'm sure that someone will chime in here. Hope you get it figured out.

[MadTing]

Post pics so that we can have a look at it.

[bulldogdaddy]

imho,i don't think 1 hr. of break in is enough before you go to 6000rpms.
there is alot of threads here on break in procedures.

[Hot Shot Merc]

It may not be the cause but the mercury racing owners manual that I received with my 2004 280 says stearnly that you must follow the recomended breakin procedure in ordor to be within warranty perameters wich states that you should always vary the throttle setting during the breakin,avoid wide open throttle,avoid full throttle acceleration,avoid remaining at a constant speed for more than two minutes,avoid sustained idle at a constant speed for more than two minutes....then goes on to say that for the first hour-do not exceed 1/2 throttle or 3500 rpm.....2nd hour-do not exceed 4500 rpm....hours 3-10 do not operate at wide open throttle for for more than two minutes......These are with a new motor wich has the computer still in breakin mode so the rev limit will be around 6000 rpm's. :)

[QUICKSILVER]

I think T-Rex said he rebuilt the same engine 3 times. He was chasing a fuel problem, but the switch boxes were the problem. He won't do a rebuild without replacing both switch boxes. Sounds like you covered the fuel system, but have someone test the components together on the engine, and replace the switch boxes.

[GPI Racing]

David,

I had a 280 that went through the same cycle. Didn't know what could cause it as we replaced or checked out everything logical. Turns out it was the ECM. Somehow the thing sent "bad info" to the cylinder that kept on failing. After replacing it the motor is running fine. (rebuilt it a couple times though to get to that point) Breaking it in the way you did shouldn't be a problem, I've done it harder than you did. I'd loan you a ECM to try but that is the least of the problem now.

Randy

[Markus]

First: This has nothing to do with the break-in procedure. It could be caused by 2-3 months old gas, but it is not very likely.

Second: What do the other piston tops look like? Do they look lean? Please post some pictures.

[David Johns]

Here is # 5.

[David Johns]

A couple more PICS

[us1]

It looks like it detonated. I don’t take a motor over 2000 RPM at 1 hour. You need to check the timing on each cylinder since it keeps melting the same one. I think you will find the trigger is off in timing on #5 and its sister cylinder on the opposite bank. Mark the flywheel at 25 degrees for each cylinder and check them all for max timing advance. It’s actually quite common to have this trigger problem. I have seen people chase it for months burning up piston after piston.

[sosmerc]

Dave, can you post your serial number? I'd like to look at the parts breakdown on your engine before I make any comments about your problem.
You said you bought the engine used.....do you have any idea whether or not the engine had been modified any from its stock configuration? Have you checked to see if there were any bulletins that might pertain to that model and serial number?
I believe a DDT can plug into the ecu and access run history...and possibly see the "fuel offset" setting. Someone may have set the fuel curve too lean.
Having a pair of EGT's MIGHT have exposed a lean condition in time to save it before disaster occurs.

I'd also be curious to see the flow chart that Tony should have given you when you got your injectors back. Is there any way you can post them for us to examine? (I'd like to compare the numbers with my set that Tony did awhile back)
Thanks!

[David Johns]

John and everyone thanks for your quick responses. My 2000 280 does not have any switch boxes or triggers. Everything is done by the ECM. I believe a Hi-PO dealers can evaluate for crossfiring with a DDT tester. Can this be done without one? Has anyone seen this much damage not following break-in? Seems a liitle extreme.

Thanks again.

[David Johns]

SOSMerc,

My serial is:OT069330. I could scan and email Tony's results.

Thanks.....

[us1]

Sorry about that, I was thinking 260. SOSmerc is right.

[sosmerc]

As we know, the ECU controls everything based on sensor input. Since the injectors were cleaned and flow tested, let's assume they are physically ok.
If there is not enough fuel pressure behind each injector you could still have a lean condition, even if the ecu is correctly operating the injectors. So I would sure check the boat's fuel system for restrictions, and check the fuel pumps output pressure.
Next is timing. The ecu controls timing and as I understand it, there's a possibility for variance here due to bad coil module (s) or faulty ecm. I don't think the DDT will pick up a timing error. You will need to index the flywheel for each cylinder and verify with a timing light that each cylinder is getting approximately the same timing. With the engine running, the DDT might tell you what timing is at the moment, but not specifically for each cylinder. (same goes for injector duration). Personally, I do not know how to test the ECU itself....and when somebody can finally figure out how to properly mess with the internals of the 555 and 538 processors, that's going to be a BIG day for us. I can't wait for a 3.0 litre PCU...come on Tony!!
Under "special functions" with the DDT, you can fire each injector, so a pressure drop test could be performed to verify that each injector is being opened and closed the same (at least you would know your harness is ok).
I don't know enough about the 280....any chance the water deflectors are in the wrong spot on the starboard side?
DO install egt's.....THEY are a GOOD thing!

[sosmerc]

Been reading my service manual (between football games) and I have a few more thoughts and questions.
Was your ECM reset after the rebuild? Re-setting the ECM puts a new Break in Mode in action. Under load, the ECM will increase fuel flow by 10% and limit rpm to 6000. The break in mode lasts for 2 hours, providing you have been running under sufficient load. Fuel off-set cannot be adjusted during the break in period.
I hope you have the correct factory manual for your specific model and serial number...it's packed full of useful information.
Also, the DDT can recall "system info" right from your engine's ECM...it gives you specific ohms info on components, all key component specs, etc. At least that info should be correct for your engine...unless someone did some component swapping!
Good luck...and keep us posted on your progress.

[2fast4mom]

As a student of 280 theory of operation (NOT an expert by any means), and as a troubleshooter by training, my first suspect would be the ECM.

If it were a fuel pressure issue, why would it consistently burn up #5 only? Maybe there is a reason for this, but I don't know it if there is.

Secondly, the ECM in the 280 is multi-tasking a wide variety of chores in real-time. It manages the timing and fuel delivery completely, along with feedback and input from the crank position sensor, throttle position sensor, and MAP (mainfold absolute pressure) sensor.

From what I have seen and heard, the crank position sensor is a go/no go proposition. If it is capable of altering the timing on a specific cylinder, I'd like to have someone tell me how this is possible. All it does is provide magnetic spikes as the toothed assembly rotates. You could offset the sensor, but this would affect ALL cylinders equally.

If you enter in the variable that it keeps burning up the same cylinder, AND the fact that the injectors have just had attention, I would look to the culprit as to whoever is in charge of fuel delivery and timing to that cylinder: Suspect # 1, ECM. IMHO only.

[sosmerc]

Hard to argue with that 2fast.....

One other thought though. What about an air leak somewhere that has been overlooked? It would have to be in an area that affects only #5. ("bleed nipple" cracked, or hose split, intake gasket or reed gasket or seal ring...anything that would allow incorrect crankcase pressure on that cylinder)
Probably a long-shot...yet I have found MANY split bleed hoses hiding behind components where they can't easily be seen.

Has anyone ever run into a faulty crank position sensor? The engine will not run with a dead cps, but is it possible to have a functioning, but faulty cps?

Merc techs I've talked with in the past say the ECU's and ECM's are generally the last place to look.?? (for the price, I'd sure like to think they are pretty bulletproof)

[sosmerc]

Any chance the flywheel is not indexed correctly? This would make the timing off on all cylinders equally, but maybe #5 runs closer to the edge than the others to start with?

[Stoker100]

Just be sure to check before assembly
ld