Mercury Outboard (not firing)

[joechristo]

I have had an ongoing problem with my outboard. It is starting and running, but the engine does not sound like all the cylinders are firing. It sounds like it tops at 4000 rpm instead of 5500 rpm.<br /><br />Only going 30, the cooling system is working ok, and it idles fine, just when trying to cruise it is not getting the speed it should. It is also slow off the line. Last year it was stalling off the line, but I think that is resolved with new fuel lines.<br /><br />What would be my first step, how would I check for spark on an outboard, a guy I work with said to just take the boot off the plug, crank it, and see if there is a spark while holding the boot near the engine block.<br /><br />Also, I know I am supposed to check for compression, but I see all these instructions to put the engine in forward, the crank it. How is this possible? My throttle locks out the starter when you put it in gear. Am I just supposed to use the idle lever?<br /><br />Thanks in advance for any replys, good forum, other forums like this have been disappearing.<br /><br />Thanks,<br /><br />Joe

 

[joechristo]

Re: Mercury Outboard (not firing)

Any Help/Suggestions/Comments?

 

[sho305]

Re: Mercury Outboard (not firing)

You would take out the plug and plug wire to it then hold threaded part of the plug to bare metal of the block and see if it is firing. Consider new plugs every year or so anyway. I get zapped every time I hold a wire so screw that. Easy to get a spark tester for $5 at autozone then you can test the strength of it as well, and should jump half inch or so at idle. Sounds like a dead cylinder or two. Check plugs, if some or one is wet after running then no fire there and check ignition. If dry plug check for gas, if multiple carbs try squirting a little gas in each of them while running and see if it picks up rpm to locate problem & clean carbs. recommend getting "muffs" to run motor on hose on land. Do not overrev it, best to keep out of gear. Much easier to work on this way and it sounds cool(to some). Check all wire connections, fuel filters, etc. too. I had a pump bulb go bad and restrict fuel, but then it dies when you gas it. I tested compression by warming it, remove all plugs then do each hole on starter about 3-5 seconds you should get highest reading. If old you can squirt a small amount of oil in there and see if it gets better-a sign of wear on the piston rings. Good luck and let us know.

 

[clamman]

Re: Mercury Outboard (not firing)

Hi,<br />I am having the same problem on my Merc 200 2.4 I just had it rebuilt, compression,spark,switch boxes,stator,timer base,fuel pump,carburators all check OK. No power out of the hole then max's out at 4500 and sounds hollow as if its restricted somewhere?

 

[sho305]

Re: Mercury Outboard (not firing)

I would check the firing order first to make sure everything is right, that thing should run like new. Check the plugs first for some difference between them. Maybe pull wires one at a time to locate a bad cylinder, the one that does not change rpm.<br /><br />And make sure that hollow sound is not from no water in there to be on the safe side.

 

[joechristo]

Re: Mercury Outboard (not firing)

Sho,<br /> I have a flush kit, I have been running it out of the water (it does sound good).<br /><br /> I got some b12 and cleaned the carbs. I tried the spark test, no luck (no spark), but the plugs are hot after running, they are new and slightly fouled, like they are running, except the middle two are half fouled. I am going to get a spark tester Friday and probably a compression gauge too.<br /><br />I will let you know how it works out.<br /><br />Thanks,<br /><br />Joe

 

[joechristo]

Re: Mercury Outboard (not firing)

Ok, now I am getting somewhere. <br /><br />I got a spark tester, but it wasn't going. Then I tried it on the block again, and I got spark on all six cylinders.<br /><br />Then I did the compression test...<br />1-105<br />2-120<br />3-120<br />4-120<br />5-110<br />6-0 - yikes......<br /><br />A couple of questions from a rookie:<br /><br />Will I still be paying out the nose to the mechanic if I tell him that the one cylinder needs to be repaired?<br /><br />Do cylinders 5 and 6 appose each other? If one has no compression, does that make the other one useless?<br /><br />Could it be a stuck piston? Or would it be an O ring or some seal instead? Should I just open up the cover and take a look, or am I at risk of breaking more of the engine if I do not know what I am doing?<br /><br />Last one, I have been studying the manual, it states that the firing order is 1-6, how do I test the firing order?<br /><br />Thanks for any help,<br /><br />Joe

 

[joechristo]

Re: Mercury Outboard (not firing)

Any help out there??

 

[joechristo]

Re: Mercury Outboard (not firing)

Ok, one more try. Any Help?