79 115 HP Blueband Mercury - Dry Spark Plug

[johnno]

Hi All,<br /><br />Although the motor seems to run fine with the earmuffs on, the 3rd spark plug (from the top)is very dry i.e. no fuel on it. The 4th flug (on the same carbie I think) has plenty of fuel on it. So far I have:<br />1. changed the 3rd spark plug<br />2. put a ohm meter on the coil for the 3rd plug to ensure there were no open circuits causing a no spark condition.<br /><br />Any assistance appreciated...

 

[JB]

Re: 79 115 HP Blueband Mercury - Dry Spark Plug

G'Day, John.<br /><br />Do you have spark on all cylinders? Are all cylinders making power? <br /><br />Running "fine" without a load not a useful indicator. You need to disable each cylinder and see if rpm drops.<br /><br />Let us know what you find.

 

[johnno]

Re: 79 115 HP Blueband Mercury - Dry Spark Plug

Hi JB,<br /><br />When I pull each spark plug wire off one at a time whilst running the rpm's drop. This doesn't happen on spark plug 3 though.<br /><br />Thanks for advance.

 

[JB]

Re: 79 115 HP Blueband Mercury - Dry Spark Plug

G'Day, John.<br /><br />Sounds as though #3 isn't making power. Did you check it for spark?<br /><br />Is this a 2 carb engine? Are the carbs 2 throat type? You may have a gummed up jet for 1 throat of 1 carb, or, less likely, a bad reed feeding that cylinder.<br /><br />If it has spark, overhaul the correct carb. Inspect the reeds while you have the carb off.<br /><br />If it does not have spark, try switching coils with #4 and see if the problem follows the coil.<br /><br />Let us know what you find.

 

[skier]

Re: 79 115 HP Blueband Mercury - Dry Spark Plug

1079 Merc 115 is a Inline 6 with three carbs.<br /><br />Craig

 

[johnno]

Re: 79 115 HP Blueband Mercury - Dry Spark Plug

Hi JB (& others),<br /><br />Swapped coils between Cyl 2 & Cyl 3 and there is still a dry Spark Plug on Cyl 3. <br /><br />Each carb supplies fuel to 2 cylinders (3 carbs - 6 cylinders) <br /><br />Is it possible that this is a fuel problem even if there is fuel on Spark Plug 4 and it is absolutely dry on Spark Plug 3?<br /><br />I am not sure if this is still a spark or fuel problem?<br /><br />Any help appreciated...

 

[johnno]

Re: 79 115 HP Blueband Mercury - Dry Spark Plug

Hi All,<br /><br />Any suggestions/advice on this problem is appreciated...

 

[Rex]

Re: 79 115 HP Blueband Mercury - Dry Spark Plug

Johnno<br /> To me it lookes to be a fuel problem.<br /> why #3 plug is not wet.<br /> You say it is a inline 6.<br /> So the carb. that not work right<br /> Is #2 carb. Easy one to get to.<br /> Have you tryed to pump the fuel <br /> when it running and it stays hard.<br /> but i would change coil.<br /> I know it does not should right but<br /> in there self just don't act the same.<br /> get some wd-40 and spray in all 3<br /> carbs. If you spray 32 crab. and the rpm<br /> go up then I would say time to rebuild<br /> that carb. or get one off of some one<br /> you know just to check it out.<br /> we are talking about idle some around<br /> 700 to 1000 rpm.<br /> adjust the idle jet the base line is<br /> turn all the way in then out 1 and 1/2<br /> i would say 2 turn.<br /> When the engine is running turn the idle<br /> jet screw in untell it start rev. up.<br /> If i remeber right it has two fuel pumps<br /> on it. Just keep in mind. that goes back<br /> to when you are pumping the fuel bob to see <br /> if it will stay hard.<br />JUST LITTLE ME KNOW IF ANY OF THESE HELPS.<br />REX A. HUBBLE<br /> (I hope) Do that on all three.<br /> P.s. Mark the screw so you can put them<br /> right back to where they were.

 

[Rex]

Re: 79 115 HP Blueband Mercury - Dry Spark Plug

Do a compression check first thing.<br />It seem nore like a port is plugged up.<br />That could be the intake or exhust ports.<br />have you thought about the reeds i not sure<br />on this engine.<br />Rex a.

 

[Rex]

Re: 79 115 HP Blueband Mercury - Dry Spark Plug

Did you find it?<br />rex

 

[sho305]

Re: 79 115 HP Blueband Mercury - Dry Spark Plug

These inline 6's have strange reeds that are on the crank, on a circular plate. They seem to be durable but are hard to inspect. Lot of times a bad reed will make bad idle and go away some at top rpm as air speed goes high in intake and the flow cannot revert back out through bad reed. May show up as puffing out through carb at idle too, not so much if carb is on more than one cylinder. May hear intake noise/popping from that cylinder or is louder intake sounds. <br /><br />Try a $5 spark testor and set for a half inch on bad coil, then I think the second winding in stator starts at 3000rpm if so equipped, and see if spark changes then. Compare to other coils too. Could be CD if coil swap does not change condition. Or, if good it is an airflow/compression problem there. Maybe crank seal, very expensive but not common.