Lost spark

[brs2baa]

I have 1985 70ETLK on a houseboat has a govoner to limit it to 3,000rpm. When I take it out it was running ok for a few hundred yards,then would missout if I dropped it to 2,000rpms it would do okay & not miss did this for awhile put in new plugs thermostat new gasline from tank to engine. None seemed to help last time out it would run fine for a little while then miss until I lowered to 2,000rpms stayed overnite on lake. Next morning it didn't want to idle when I started it I got it out & it was going along at 2,000 rpms then seemed to drop to 1cyd then I shut it off & it won't start now. Would like to fix myself if they have to come out to it $$$$$$$$. Don't seem to be getting any spark. Do you think it could be the CDI black box? Any way to check it? Any ideas I can try? Its a monster with no motor. Help Please Thank You

[boats.net]

Not sure how they governored it but try to disconnect what ever it is.

[brs2baa]

Thanks for the reply will try to figure it out will rev 6,000 r's with fast idle up but has always only went 3,000 in gear. But I went over to ckeck it today & it started & ran at above 3,000 r's with fast idle up pulled top plug wire no diff pulled 2nd plug wire no diff put them 2 back on & pulled bottom one it would die every time I pulled it. Could not get it to start anymore. Do you think it could be the 2 coils? I put new plugs in & tried another one I knew was good but I can't see it fire when I take out plug & ground it.Would be thankful for any ideas. Thank You brs2baa

[jb123]

you pull the plugs and no change but are you getting spark?

sounds like dirty carbs.

[brs2baa]

Thanks for the reply. I pulled the plug wire off & no diff in way the motor ran . Checked for spark didn't have any, that is why I thought it was CDI or Coil. Seems when it will start now only runs on bottom cyl. It Has been acting weird for awhile but usually it will start & run like a charm at first then after you go few hundred yards or so then it will miss if you ease up it will run okay until now & it won't start most of the time, when it does now it seems to run on only bottom cyl. I grounded the plug & no spark. Has me stumped. Can pull wire off top 2 cyls & no change in way motor runs, when it will start, only one on bottom if you pull wire it will die every time. But you have to keep it above 3,000rs or it will die makes me think it is only running on one cyl. Cause it would idle & run like a new one until this happened. Had cleaned carbs & they seem to be okay. Its a 85 motor but get very little use. Thanks for any help. brs2baa

[jb123]

swap coils see if the issue follows coils or stays.
check and clean grounds.

i really find i hard to believe it will run on one firing cylinder.

[brs2baa]

Thanks for reply, will try that will move bottom one to top & see what happens. Yes it does run with top & middle plug wires off,but it has to stay above 3,000rs or it dies. Again thanks that will tell me if it is coil. Thanks brs2baa

[brs2baa]

Changed Coils still only fires on bottom cyl so not coil. Ordered CDI {brain] unit got it today installed it started & RUN LIKE A NEW ONE. For anyone having trouble like I was. Thanks for the posts & help you can't pull those plug wires now without a good shock. Thanks to all & safe boating.

[Tucker]

Hmmm this one slipped under the radar. I think it's fair to say that CDI's are voodoo to most of us mortals. Is there a simple pass/fail test for CDI's? Is the failure frequency for CDI's on a 24 yr old motor that low that it wasn't suspect in this case?