My merc 2.5 liter not running right.

[shelbydriver]

My merc 2.5 liter not running right.

I have a 94 merc 200 Hp 2.5 liter xxl. It wouldn't stay running and seemed to be missing something in the HP range. Symtoms include backfiring thinking timing problem. Compression equals 90 cold and just did the head gaskets. Took to the mechanic for electrical diagnostics. he only charged charged me 60 as I did not have a DVA mete and said the stator was putting out good.HoweVER he said the inner switch box is only hitting 60 dva's or volts on 3. Couldnt afford a new switch box so mechanic number two loaned me a used one. Wired it in and still the same problems. Sounds rough, plugs wet with fuel Backfiring. Any guesses here? Fuel is ok along with filters. How to check tim ing. I have number one on TDC. Should the pointer be at 4 degrees? The book is kind of iffy. Thanks in advance. Wheaticat@aol.com. The beer's on me.Fishing season is saturday first tournement.

 

[rodbolt]

Re: My merc 2.5 liter not running right.

Re: My merc 2.5 liter not running right.

hello<br /> 60 volts on a peak reading meter is marginal. its at the break where itaint gonna spark. you may have a bad switchbox but I rather doubt it. leave the timing issue alone. its a mechanical link and unless some on wrenches on it its either works or its broke. I would suspect that with 3 cyl with 60 volt output from the switchbox you have a bad stator. if the stator output is ok it has to be the switch box. but like I say garbage input equals garbage output. the switch box only rectifies and stores the ac to dc the trigger switches the scr and fires the coil primary. the voltage is stepped upat the coil not the switch box. if 60 v out from the switch box I would suspect only 60volts in. and 60 aint enough.<br /> Idont have my merc manuals out but 100-120 is about the minimum spec for primary ign voltage much less and the system tanks.<br /> good luck but recheck that stator.

 

[WillyBWright]

Re: My merc 2.5 liter not running right.

Re: My merc 2.5 liter not running right.

If you have good DVA to the remaining 5 cylinders, then your stator shold be okay. When power is sent out from one switchbox, it is also passing through the other switchbox. Then when the magnetic polarity swiches at the trigger, the process is reversed. The switchbox that you thought was good could be the bad one.

 

[shelbydriver]

Re: My merc 2.5 liter not running right.

Re: My merc 2.5 liter not running right.

Ok Looks like I will have to try another switch box. I forgot to post I melted the voltage regulator the bottom one. I was running the engine without a battery at one time, and running on a dead battery. I was adjusting the idle with the idle screw and noticed that it changes the timing too. That is why I am thinking maybe the adjusting nut came loose. I will ponder the situation and just drop it off at the mechanic again it looks like.