Help Inline 6 Demon From Hell

Hey guy thanks in advance for any help you can give.

What i have is 1984 inline 6 merc 115. Did not runworth 2 hoots. Ran compression test 120 psi all cylinders. Next checked for spark good spark all 6 installed new plugs. Pulled carbs did a full cleaning and rebuilding new needles and seats and a new fuel pump also checked reeds while carbs were off. Did the sync on timming and carbs. go to the lake idles beautifully, but as you throttle up when the timing advance hits its stop it just laid down. So broke out timing light and when at full advance 2,4,6 cylinders loose spark. Thought must be bad timing ring, picked up new one and installed still does same thing. what gives.

thanks no hair left Rob

Re: Help Inline 6 Demon From Hell

By "timing ring" do you mean trigger?

If so, be sure to measure the resistance of the stator's Hi Speed and Low Speed ign windings; if they're out of spec it'll cause all kinds of screwy running problems.

If you did replace the stator and not the trigger, it'd probably be a good idea to do a resistance check on the trigger. Also wiggle its wires around, maybe you have a break in a wire that acts up only when you advance the timing and the wire gets stretched. Just a thought.

Otherwise you might just have an ign box that's giving up the ghost at higher rpm. One way to rule that out would be to swap ign boxes and see if the problem transfers to cyl's 1, 3, & 5. If so, that's your problem.

Note that when one ADI ign box starts going bad, likely the other one is gonna fail to. It's known that one bad box can take the other one out.

I prefer www.boatfix.com for replacement ign parts but feel free to browse this site for same!

Here's some info which may help you with your troubleshooting:

http://www.boatpartstore.com/mercreadings.asp

http://www.marineparts.com/partspages/Outboard/trouble2.htm

Note on this 2nd link they talk about disconnecting the bias wire between the 2 ign 'packs'. You may find this is your problem and you'd definitely need to replace both ign boxes.

http://outboardparts.com/mercury/troubleshooting/troubleshooting10.htm

HTH & let us know what you find..........ed

Re: Help Inline 6 Demon From Hell

thanks i will try the stator test and yes it was the trigger i replaced.

Re: Help Inline 6 Demon From Hell

Ok i tested everything stator, trigger, all within spec. start motor fires on all six at idle throttle up and lose 3 cyl. unhook bias wire no change. hook bias back up and remove wires from rectifier runs great put new rectifier on runs good for about a block and then 3 cylinders go dead again. pull wires off and runs again. test rectifiers with meter first one tests bad but new one tests fine again stator tests fine. any thoughts. thanks Rob

Re: Help Inline 6 Demon From Hell

If I recall, if having a good rectifier hooked up affects the ignition, the stator is bad (regardless of whether its resistance readings are good or bad).

Something about the charging windings interfering with either the Hi or Low Speed ign windings. About the only thing it can be, since there's no other interplay between the ign and charging circuits.

You may need to pull the stator and check it for burn marks which would be a sure sign of failure.

Another test would be to take resistance readings at ambient temperature and then stick the stator in a toaster oven and heat it up to about 140 deg F. If the resistance readings change drastically, she's shot! I had an 85 HP with marginal readings and after sitting in the hot sun for a few days, the Hi-Speed windings' resistance was twice what I measured previously! Needless to say the stator was shot and the motor ran great after replacing.

One last thing to try before condemning the stator is to swap ign boxes and see what happens. Until you do there's always the possibility that the ign box is bad.

HTH...........ed

Re: Help Inline 6 Demon From Hell

already switched switch boxes. I just took stator off for inspection. thanks Rob

Re: Help Inline 6 Demon From Hell

I had the same problem with a early 90's Merc. It would run great in the yard but as soon as I would dump the boat in the water and try and take off it would fall flat on it's face. I pulled my hair out for two weeks until I finally broke down and installed a new stator (ouch) and voila she ran like a raped ape.