Here is a challenge for all you techs????????

**bill mason** · 10-23-2021, 04:31 PM

I have had this problem for YEARS on my 280. If I run it over 5000 rpm no problems. When I run it under, like 4000-5000 it develops a miss. Feels like a fouled plug. If I run it back up in rpm it will most of the time run fine? If I keep it at lower rpm it will sometimes completely lose the cylinder. On my DDT it shows #6 ignition fault. If I switch coil, spark plug, and spark plug wire to another cylinder the fault doesn't go with the parts from #6?? Run it again and #6 will be the fault. I thought it was the female connection in the electrical harness as there is no medal sleeve in #6 hole. When I did continuity test there is no wire connected to #6. Eight holes 7 wires coming out. Thats not the problem. On the DDT static and running test shows all components are fine. Today I ran a different ECU (15 hours on it). Same problem?? Ran fine above 4000 rpm. At around 4000 it developed the miss. Ran hard and it "cleaned" itself out and ran fine. Put on the DDT and fault is in #2??? What the hell?? Mother has got me over the edge. I am out of things to try. Any of you guys have any thoughts on this? Appreciate any ideas as I have eliminated everything I can think of. Oh I don't run the champion plugs, they don;'t work.

**XstreamVking** · 10-23-2021, 04:40 PM

How old are the switch boxes?

**Dave S** · 10-23-2021, 05:08 PM

I will trade ya for a 2.0 150 that will fill ya needs......under 5000 .... No issues.......

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**Dave S** · 10-23-2021, 05:08 PM

That..... CDM motor........

**LakeFever** · 10-23-2021, 06:08 PM

Broken reed

**MrG** · 10-23-2021, 06:37 PM

Should to a static pressure check on injectors could be free flowing an wile your at it the orings could leaking and over rich condition fouling plug . If a reed is broken manifold vac would make a over rich Accross the system wouldn’t idle ..just my past experience with Mercury 2.4/2.5

**rgsauger** · 10-23-2021, 09:37 PM

I just bought two new Sierra German switch boxes today for same reason.

**bill mason** · 10-24-2021, 03:42 AM

Thanks for reply guys. No switch boxes on 280. Here is a little more info. The electronics are off a 2007 complete 280 I bought new. I have had several 280 power heads back when I was racing but always ran 260 electronics on them. These electronics were taken off the complete engine, have less than 200 hours on them. Completely removed electronics 25 hours ago. Injectors were flowed and checked 25 hours ago. Problem existed long before that. Again, runs fine above 5000 rpm. Will run 104 mph, no problem @7500rpm 27 Hoss prop, and 100 mph @8000 rpm (1 ecu no rev limiter) 24 Hoss prop. I'm not down playing you alls thoughts just having a thought. If it was a reed fouling the plug then why when I move that plug to another cylinder why doesn't DDT show that folded plug in the cylinder I moved it to? It is worth pulling the reeds and looking at them. It idles fine. A good friend suggested I run it when its dark to see if I see any arching. Going to try that also. Thanks all for replies. Its ok to just keep rps up but I'm a hard headed wannabe mechanic that doesn't like a mechanical "thing" to get the best of me??

**LakeFever** · 10-24-2021, 04:47 AM

Soak the whole ignition system with wd40 and try it

**MrG** · 10-24-2021, 10:34 AM

You can bore scope the reeds.You might want to do a power output to coils taking it out of the probable cause and check the trigger output too

**half fast** · 10-24-2021, 11:21 AM

Have you measured the air gap between the crank sensor and reluctor wheel ? It’s adjustable on some motors. It is something we check on opti motors . Super critical on mercruiser with a cps . Hf…

**Dave Strong** · 10-24-2021, 12:07 PM

Originally Posted by bill mason

Thanks for reply guys. No switch boxes on 280. Here is a little more info. The electronics are off a 2007 complete 280 I bought new. I have had several 280 power heads back when I was racing but always ran 260 electronics on them. These electronics were taken off the complete engine, have less than 200 hours on them. Completely removed electronics 25 hours ago. Injectors were flowed and checked 25 hours ago. Problem existed long before that. Again, runs fine above 5000 rpm. Will run 104 mph, no problem @7500rpm 27 Hoss prop, and 100 mph @8000 rpm (1 ecu no rev limiter) 24 Hoss prop. I'm not down playing you alls thoughts just having a thought. If it was a reed fouling the plug then why when I move that plug to another cylinder why doesn't DDT show that folded plug in the cylinder I moved it to? It is worth pulling the reeds and looking at them. It idles fine. A good friend suggested I run it when its dark to see if I see any arching. Going to try that also. Thanks all for replies. Its ok to just keep rps up but I'm a hard headed wannabe mechanic that doesn't like a mechanical "thing" to get the best of me??

Have you tried swapping that injector to another CYL?

Dave

**PanRonnie** · 10-24-2021, 01:30 PM

Originally Posted by bill mason

Thanks for reply guys. No switch boxes on 280. Here is a little more info. The electronics are off a 2007 complete 280 I bought new. I have had several 280 power heads back when I was racing but always ran 260 electronics on them. These electronics were taken off the complete engine, have less than 200 hours on them. Completely removed electronics 25 hours ago. Injectors were flowed and checked 25 hours ago. Problem existed long before that. Again, runs fine above 5000 rpm. Will run 104 mph, no problem @7500rpm 27 Hoss prop, and 100 mph @8000 rpm (1 ecu no rev limiter) 24 Hoss prop. I'm not down playing you alls thoughts just having a thought. If it was a reed fouling the plug then why when I move that plug to another cylinder why doesn't DDT show that folded plug in the cylinder I moved it to? It is worth pulling the reeds and looking at them. It idles fine. A good friend suggested I run it when its dark to see if I see any arching. Going to try that also. Thanks all for replies. Its ok to just keep rps up but I'm a hard headed wannabe mechanic that doesn't like a mechanical "thing" to get the best of me??

If you tried a different coil and a different ecu and the problem remained with the same cylinder that would leave the wire loom
intermitant due to vibration at that particular rpm
on the look out for a second wire loom!?
i was also thinking the 280,s had a shift switch?

**bill mason** · 10-25-2021, 11:05 AM

First and most importantly, thank all of you for your time and suggestions on this. I don't know anyplace where so much boating knowledge can be found in one place. I decided to go back to the very beginning and preform every one of you alls suggestions. When I first put on the new ECU the DDT showed the ignition fault had moved from #6 to #4?? on the new ECU. This threw me a curve as old ECU fault was #6 always! Today starting from the beginning again, I erased all the fault codes and ran a half of a tank of gas. I couldn't get the engine to misfire as it had over the past few years?? (not to much fun with stock rev limiter at 6800rpm). Checked and NO IGNITION FAULTS?? WTH This sure points to the old ECU causing the problem. No clue why new ECU first time showed faults. Sent the ECU to Brucato. Thanks again everyone for your time and sharing your knowledge!
For me, not much more enjoyable things in life than hearing a two stroke talking to you at 8300 rpm and running over the century mark.

Have fun be safe guys

**bill mason** · 10-30-2021, 07:28 AM

Well crap, Brucato doesn't work on motorola ECUs. I did find a guy on u tube that does. I sent the ECU to him to look at. In his email he told me "that if I have an injector problem, it will damage the new ECU I am running now that now has no faults". I found an old post that was somewhat like this, but the question never answered is this, how can an injector problem damage (driver etc) in the ECU. My understanding is the ECU runs the injector not the other way around?? At worst case the injector would be stuck open or closed? What am I missing? The injectors were cleaned and flowed by Brendon Powers 20 running hours ago. Problem existed before and still have after the service. Thanks in advance again for any thoughts guys