HELP!!!!! merc engine problems

[robertsexpress]

HELPPPPP!!!!! Merc motor issues

Ok guys I need some help here. I have a 18 foot express with a older 90 merc on it. Boat has always ran great and never had any issues with it.
It sat up for several weeks/months without being used or ran at all. Back in October I took it to my buddy's camp and we went fishing. Headed out and my buddy was driving as I didn't know the area that well. After a few minutes going down the bayou motor starts to cut out. Speed dropped about 10mph, we stopped it and revved it up and it revs fine but once you put it in gear and take off it starts the same thing again. I figured it was carb issues from siting up without running.(I did use some gas with ethanol in it before it sat up, I also used some ethanol treatment In it as well)
I brought it home, and it sat there until Feb/March due to hunting season. Sometime around March I changed spark plugs and put a can of seafoam in gas tank and I ran it several times, for about 20 minutes or so on the muffs in driveway. Figuring that wasn't going to fix my problem but hoping it was just gummed up carbs and that maybe the seafoam would clean it out. I took it out Monday (memorial day), it fired right up and idles fine like it always has, but when you pour the throttle to it, it jumps on plane good but does the same thing. It will run and push boat down the river but there is a steady miss/hesitation to it and it is running 10 mph slower than it does normally.
I have been told everything from dirty carbs from some non ethanol gas that sat up in it to Power pac bad and everything between.
If anyone can help me out before I have to bring to shop and pay a arm and a leg I would appreciate it. I can do somethings myself and would prefer to do It myself if possible.
Please tell me this is something someone else has had issues with and can help me out, and tell me that this is not going to cost me out the behind.
Engine serial # 0G142156

thanks

[JOE54]

check spark and compression ,check fuel filter for restriction if you find brown looking particals will need to clean everything from filter to tank and replace degrading hoses, do not continue to run this engine until prob is found or it will get yo behind, hope this helps ya JOE

[robertsexpress]

check spark and compression ,check fuel filter for restriction if you find brown looking particals will need to clean everything from filter to tank and replace degrading hoses, do not continue to run this engine until prob is found or it will get yo behind, hope this helps ya JOE

thanks Joe

[EuropeanAM]

A little more detail on the fuel stuff:

FUEL LINES AND PERFORMANCE PROBLEMS

[robertsexpress]

Went out and worked on motor today. Had it running and was checking the spark plug wires. Pulled off the top plug wire and even though I had on gloves it lit me up pretty good. I dropped the wire and could see the fire coming out of the back of the boot.
could it be something as simple as a bad spark plug wire.
i never have easy fixes like this so I am doubting that could be it, but would be thrilled if it is something so easy.
thanks

[JOE54]

what about other 2 grab them,heeeeeheeeeee

[EuropeanAM]

Inspect that boot (engine OFF preferably) for any signs of tears, splits, etc.

With the wire OFF, the spark will do it's best to find a route to ground (if it can't find one through YOU, it will look for alternatives).

[robertsexpress]

Ok guys, need more advice. I got new wire and changed it out, also changed spark plugs at same time.
when I changed the spark plugs, I realized the top plug, which was the one I changed wire out on, was completely black while the other 2 were clean looking.
i am attaching a pic of the spark plugs, the top plug is pictured in the middle.
is it possible that the bad wire could be the reason for this or something more serious?
i really can’t be lucky enough to change out a wire and plugs and that be all.
havent had chance to take to lake and run yet, hoping this is a quick fix and nothing more.
any advice is appreciated.
here is a pic of the plugs:

[robertsexpress]

[robertsexpress]

Definitely not the fix, just got back from running it and still doing exact same thing,
planes off good but cutting out and still running bout 10pmh slower than normal.
running fine at slower speed just not WOT.
carbs maybe? Need advice.

[JOE54]

check for spark with timming light while under load on top cyl, yes could be in carb eliminate all else first

[EuropeanAM]

check for spark with timming light while under load on top cyl, yes could be in carb eliminate all else first

^^^^^

[robertsexpress]

Ok so I am about to go crazy with this. Motor is cutting out/coughing at low idles speeds, mid range and WOT. It will get up on plane but just cuts out almost constantly but every now and then it will not cut out at all for a minute or so but still has no rpms or speed. It will plane off and hit about 28-30 MPH (which is about 10-12 Mphs slower than normal).
I ran a gallon of gas with full can of seafoam thru motor hoping to clean up carbs (something I seen on youtube), I have changed the fuel filter, spark plugs, tested spark with tester, checked compression (all 3 cylinders 120 psi). Had a buddy look at it this weekend and while running he decided to pull spark plug wires, nothing changed in way motor ran when he pulled each one, but each on did shock him pretty good from back of boot where he was holding it.
I noticed battery has been dead a good bit lately, charged it Thursday and ran boat Friday and then Saturday battery was dead again. Put charger on it for several hours and went to leave buddy's camp and motor started up, took charger off and put up, motor died and just that quick it wouldn't start back, battery dead again. Trolled to landing and put boat on trailer.
Could all of this be from battery being bad and maybe messing with the fire or something?
When problems originally occurred the first time, battery was dead and we swapped out battery with my buddy's battery and then we noticed it cutting out.
Jus trying to figure this out. Please provide any answers or theories anyone may have.
thanks

[robertsexpress]

Just went out and checked voltage regulator and found 2 wires coming off the regulator melted together. I can see metal where I pulled them apart, think it could be something as simple as changing regulator and new wires and maybe will produce better spark and quit misfiring? I am truly at a loss and tired of fighting with this thing.
thanks,

[JOE54]

very possible make sure charging system is operating correctly , would use oem regulator

[robertsexpress]

Ok so after changing the voltage regulator and all new spark plug wires it is still doing the same exact thing. I am starting to think maybe clogged jet on carb?
Seems to run good for about 1 minute then it starts to "cough". Went to lake to run it and it starts well but coughs and then cuts out when running. Planes off but cutting out.
Could it be that carbs just need cleaning? Top plug still not burning correctly, could be because of no fuel going to it.
I have been trying to do this myself to save money from taking to Outboard mechanic but I cant figure this out.
Please someone help me out
thanks

[robertsexpress]

Please someone give me some advice. I am just before putting my rig up for sale. Can't seem to figure it out.
So far, I have replaced complete fuel line, fuel filter, voltage regulator, new spark plug and wires, cleaned carbs (took all 3 off and cleaned out), did spark test, compression check 120 psi on each cylinder, and still cutting out. I did notice when cleaning carbs that the top carb float was stuck so I corrected that. Really thought that was it because when I started it up it idled so well and the "cough" was no longer there. Took it out to run today and had hope of it being fixed. It started right up, idled fine and when time came, I got on it and it launched out the whole and them started cutting out again. Now it seems to cut out and start to loss power. Not really cutting out at slower speeds but when WOT it cuts out and starts slowing down even though I have not changed throttle at all.
Could there still be issues in carb, is it electrical or what? I am just before throwing in the towel.
Someone please give me some advice so I can figure this out. Probably should have just taking it to shop but have been trying to fix myself and learn more about my motor.
thanks,

[JOE54]

yes it could be running out of fuel, run on seperate fuel supply[eliminate boat tank] as problem

[Lowerider58]

In post #9 you say that you tested spark with tester. Did you check spark while running under load with a timing light as suggested?

[leonreno]

You said battery kept dying, I would try a new battery, or at least have the battery load tested. If the battery is bad could be causing the problem with the regulator. Might also need to test the stator.