1984 Mercury 115 looses Cylinder

[Dragline]

Hello and thanks in advance, My 115 Horse Mercury has served me very well until today.<br />It cranks fine and launched out of the hole like a rocket as usual.<br />after ten minutes at (wot) it seemed to loose two cylinders (guessing here)<br />Changed plugs and ran it this afternoon and same thing.<br />Runs out fine and after maybe ten minutes it starts loosing power rather quickly.<br />Primer bulb is good and fuel supply is clean.<br /><br />Any help will be surely appreciated. <br /> <br /> Mike

 

[KCLOST]

Re: 1984 Mercury 115 looses Cylinder

You need to check the spark on all the cylinders to confirm. Spark + Compression + fuel = fire ...<br /><br />So start there.. <br />If I had to guess this could be a switchbox.. Getting warm and failing at higher temps...

 

[jimmbo]

Re: 1984 Mercury 115 looses Cylinder

sounds like a stator or switchbox problem to me too.

 

[Dragline]

Re: 1984 Mercury 115 looses Cylinder

Thanks Mucho Chief and Jimbo I'm headed to the Bank and then to the boat parts warehouse (May have to rob an armored car first).<br /><br />Going to do a compression test today and will post the results.<br /><br /> Thanks again<br /> Mike

 

[Dragline]

Re: 1984 Mercury 115 looses Cylinder

Just pulled the cover and much to my dismay there are two switchboxes ! This opens a whole new can of worms, Obvious question of the day .<br /><br />How the heck do I tell which one to replace ?<br /><br />(Lordy I respect mechanics)<br /><br /> Thanks <br /> Mike

 

[stalker170]

Re: 1984 Mercury 115 looses Cylinder

Mike,<br /><br /> Like the boys said, You need to start and see if you have lost you spark or you have a compression issue. It looks like you have jumped to the spark for a reason. Did you already do a compression test? If you did, give us all four cylinder readings. Than we can guide you through the switch box or stator issue. When I lost my Stator, I lost all spark to all four cylinders.<br /><br /> Stalker

 

[Dragline]

Re: 1984 Mercury 115 looses Cylinder

Hi Stalker and Yes I did a Comp. Test<br /><br />1. 125<br />2. 125<br />3. 122<br />4. 128<br />5. 126<br />6. 125<br /><br />These are on a cold engine.<br /><br />all cylinders are firing this morning and I'm going to put the muffs on her and use a hair dryer to simulate engine heatand see if I can locate which Pack is bad<br /> Thanks<br /> Mike

 

[sterritt]

Re: 1984 Mercury 115 looses Cylinder

Ahh, for starters, don't just go blindly replacing parts unless you've allready got a parts engine on hand or something. There are 6 coils, two switchboxes, a stator, a trigger, and wiring in between and it still could be overheating or fuel related.<br /><br />Go in this order, and when you find something wrong, stop and fix it, then move on.<br /><br />Check the compression.<br /><br />Check for any loose wiring.<br /><br />Check for spark on all 6<br /><br />Get the book and check stator & trigger winding resistance.<br /><br />Verify fuel pump is working correctly - if the fuel pump is working, then so is the fuel lines/filters leading to it.. if not, then it could be any of those items that's at fault or the pump itself.<br /><br />Verify engine is not overheating.<br /><br />Unless you've got it running so rich that somehow it fouls plugs at WOT (doubt it's even possible) chances are you've got an intermittant spark problem. Every now and then it's possible to have an intermittant fuel problem.<br /><br />Next time it starts acting up, take a pair of insulated pliers and start disconnecting the plugs until you find out which cylinders are not firing (when you pull one of these, the engine performance will not change). If you can't find something wrong with the spark, try the squeeze bulb - if that makes it run right, you've got some sort of fuel delivery (to the carbs) issue.<br /><br />Good luck,<br /><br />Jon

 

[Dragline]

Re: 1984 Mercury 115 looses Cylinder

Took it out and ran the blasted thing.... Still no change.<br />The bright spot is that I called a Mechanic and he's on his way to diagnose the problem.<br /><br />Should have done that to begin with.<br /><br />Thanks to all you that have tried to help and I'll be eternally gratefull.<br /><br /> Mike

 

[Dragline]

Re: 1984 Mercury 115 looses Cylinder

Well Just Fine !<br /><br />The motor is loosing number two piston .<br /><br />The outboard mechanic says it has been going bad from some time and he recomends that i scrap the old doll and buy a new engine and that my engine wasn't worth repairing due to cost .<br /><br />So if anyone has a good 100 to 115 Horse Mercury Or Mariner outboard for sale in Florida let me know.

 

[i610288]

Re: 1984 Mercury 115 looses Cylinder

Well I'm no mechanic by any means,but if youre compression is good on the number 2 cylinder, how could he say it's going bad?

 

[emckelvy]

Re: 1984 Mercury 115 looses Cylinder

Did the mechanic find aluminum being thrown off the piston crown onto the spark plug? If that's the basis for his conclusion that you are "losing" #2 cyl, you may need to readjust the ign timing. You may be losing material off the piston due to detonation.<br /><br />The timing on an ADI motor should be no more than around 18-19 deg BTDC when checked at cranking speed. Regardless of what the sticker on the motor says.<br /><br />You must also use a good grade of non-alcohol fuel, as blended fuels will run leaner and lead to detonation.<br /><br />The carbs should also be checked for blockages in the jets (pull the float bowl cover and check the needle/seat, pull the main jet plug in the front of the carb and blow air thru the carb's passages), as restricted fuel flow will of course cause a lean condition.<br /><br />Remove the float bowl vent jets as they cause the motor to lean out in the midrange, for economy. Unfortunately, with the fuel quality nowadays, it usually leads to piston problems. These vent jets are brass with a screwdriver slot, located on the outside of the carb where you can see them, in the top of the float bowl cover. You will absolutely not hurt anything by removing these jets. You may use a bit more fuel at midthrottle, but that's better than burning your motor up!!!<br /><br />Another mandatory thing to do, if your motor has an Idle Stabilizer module, Remove It Now! This thing was a band-aid effort by Merc to settle out the I-6's idle speed characteristics, but when they fail, they advance the timing and cause detonation/destruction of the innards. Better to adjust the carbs a bit rich for best hole-shot response, and jack up the idle speed a hair so she'll not die when placed in gear.<br /><br />HTH, if your mechanic can't give you a concrete reason for his conclusion, find another one who knows Inlines! You can do this stuff yourself with the help of places like this, and a good manual such as the Seloc mercury book.<br /><br />Good Luck........ed

 

[Dragline]

Re: 1984 Mercury 115 looses Cylinder

Thanks again for all the help...I just sold the boat and along with it the Engine from hell !<br />Now someone else has the problem child and I have a new Dusky with twin 115 Johnsons.

 

[Clams Canino]

Re: 1984 Mercury 115 looses Cylinder

Originally posted by Dragline:<br /> Well Just Fine !<br /><br />The motor is loosing number two piston .<br /><br />The outboard mechanic says it has been going bad from some time and he recomends that i scrap the old doll and buy a new engine and that my engine wasn't worth repairing due to cost .<br /><br />So if anyone has a good 100 to 115 Horse Mercury Or Mariner outboard for sale in Florida let me know.

Horsecrap on BOTH counts. #2 isn't bad or it would show in compression test. And even so an overhaul is affordable and prudent given the worse choices (like a Jonnyrude).<br /><br />-W

 

[ladano]

Re: 1984 Mercury 115 looses Cylinder

For the do-it-yourselfer, how much would a rebuild cost partswise.

 

[Clams Canino]

Re: 1984 Mercury 115 looses Cylinder

Using aftermarket parts sourcing (Brunswick Mercury rapes you), you could spend about $200 to $600 on parts to totally overhaul the thing depending on how extreme you wanna go. <br /><br />$200 assumes you just replace one bad piston, all the rings, and the end-cap seals. $600 assumes you replace every piston, gasket, and needle bearing in the thing, and do the carbs and fuel pump over.<br /><br />-W

 

[ladano]

Re: 1984 Mercury 115 looses Cylinder

Thanx, does someone make a master overhaul kit? Just in case its not electrical.

 

[LubeDude]

Re: 1984 Mercury 115 looses Cylinder

Originally posted by Dragline:<br /> Well Just Fine !<br /><br />The motor is loosing number two piston .<br /><br />

I say a big (BS) to his statement, Like others have said, what was he basing his findings on, I say its electrical.

 

[Clams Canino]

Re: 1984 Mercury 115 looses Cylinder

Originally posted by ladano:<br /> Thanx, does someone make a master overhaul kit? Just in case its not electrical.

Not "per se" as the scope and depth of detail of every overhaul is different. But when the time comes shoot me an email and I can try to help you figgure out what you need as opposed to what's all out there. <br /><br />Start with a compression test too....<br /><br />-W

 

[LubeDude]

Re: 1984 Mercury 115 looses Cylinder

Originally posted by Clams Canino:<br /> Start with a compression test too....<br /><br />-W

He already did it.<br /><br /><br />1. 125<br />2. 125<br />3. 122<br />4. 128<br />5. 126<br />6. 125