225hp offshore timing problem/misfire/flywheel runs backwards

[roncofish]

I have a 1994 3.0L carb mercury offshore outboard.
The engine ran great for 90 minutes, then started to run rough, like a couple of cylinders were not firing. We ran the boat back to the slip, it took about another 30 minutes. When tied up we ran the engine at idle and it runs rough and misfires every now and then. Not spitting gas out the carbs, it sounds like a cylinder or two just misfires. When the throttle is brought up to about 2000rpm the engine shutters.

I have replaced the stator, plugs, rebuilt all the carbs, checked and replaced 2 reeds and the reed plate gasket, replaced all the bleed hoses, checked all the CDM modules with a meter and even swapped 3 at a time with new ones, and performed a compression test (all were 95 PSI). I even put on an auxiliary 6 gallon gas tank to be sure the gas was OK. After all this the problem stills exist. The problem seams to be getting a little worse because now the engine has a hard time staying running at idle. When it does run at idle and when the engine misfires, it runs backwards and I shut it down. I restart it and it runs the normal direction, then when it misfires again the flywheel stops for a fraction of a second then runs in the opposite direction.

The last thing I did was check the timing. It is supposed to be about 7 degrees atc at idle. It reads about 1 degree btc. When I increase the throttle quickly, the timing advances to about 20 degrees btc like it is supposed to. I have since checked the throttle position sensors and it reads good, but no matter how much I turn it one way or the other I can not get the timing to get past 1 degree btc and it belongs near 7 degrees atc. I have it set like the shop manual states at this time. I have also checked the temp sensor and the flywheel position sensor, all check ok. I did recheck the stator bobbins and the flywheel key to be sure all are still good and they are.

Any suggestions would be appreciated.
Thanks
Ron

 

[sschefer]

Re: 225hp offshore timing problem/misfire/flywheel runs backwards

Sound like the only left is the ECU.

 

[roncofish]

Re: 225hp offshore timing problem/misfire/flywheel runs backwards

That is what I thought but everyone I spoke with at 3 dealerships states they never go bad or they have never replaced one. That is why I do not want to spend the $800 on somehting that can not be returned.

 

[Faztbullet]

Re: 225hp offshore timing problem/misfire/flywheel runs backwards

The timing is controled on that engine by the ECU, it looks at rpm,throttle position and engine temp and has a built in idle stablizer. The timing should be near 0 unless rpm is 450 or below then it is advanced in 3 degree increments. Set the engine up to idle about 700rpm in gear buy using the idle mixture screws on carbs 1st and TPS last. The engine will run with a ECU failure as bobbin's in stator take over. What I think is happening is your rpm is to low and sync/link and carbs are out of adjustment causing a lean spit that causes engine to stop and kick back reversing it.

 

[roncofish]

Re: 225hp offshore timing problem/misfire/flywheel runs backwards

I have set up the link and sync already but will check again today. The engine does run at about 800rpm when it idles before it spits and runs backwards. When it runs at 800rpm it should be about 7 degrees atc and it is closer to 1 degree btc. Remember the engine ran great for 90 minutes then this started happening. Even if I change the position of the throttle position sensor from one range to the other the indle timing does no change much from 1 degree btc. but the timing does advance toward the 20 degree mark when throttled up.

 

[roncofish]

Re: 225hp offshore timing problem/misfire/flywheel runs backwards

Also I have read in the manual that the stator on my engine takes over in the event of an ecu failure. Is there a way to disconnect some wire on the ecu to make that happen for sure?