Lack of power

[sblanco]

Hi All,

I'm hoping someone can help me out. I have a 1991 Merc Force 120 with a erratic lack of power. I'll first mention that this is a new rebuild, new crank, pistons, seals, bearings and gaskets. The engine starts up good and idles fairly decent. While on the water and attempting to accelerate out of the hole there is a bog and no power. RPM's slowly increase and then all of a sudden it goes and runs good and strong. once on plane it runs smooth but if I stop and try again, same thing lack of power and sometimes feels like a misfire. I've set ignition timing and the plugs are also new. I'm not sure what's going on. I'm thinking coil issues?
I'm hoping someone can give some thoughts on this as to what I should attempt or test next. The coils look ok but I'm sure could be failing under load? How to I test them?
I guess I should also mention the rebuild was done due to piston skirt/ring failure and lack of compression on two cylinders.
Please any thoughts would be appreciated.

Thanks
Scott

 

[TWPilot]

Too rich on the low idle screws.

 

[sblanco]

Thanks. I can take a look at that and see. What’s the base setting for the screws?
Thanks
Scott

 

[racerone]

Which cylinders were low on compression ?---Did you determine the cause of this failure.----Did you correct the problem...---Coils suspect , then test them !----Does spark jump a gap of 3/8" or better on all leads ? ----Run with a timing light one cylinder at a time and observe spark.----Open low speed mixture needles 1/8th turn at a time to see if bogging goes away.

 

[jerryjerry05]

The linkage set right?
Make sure both carbs butterflies move at the same time?

 

[Poormansboating]

Sounds like linkage setup to me also. Try doing the link and sink setup. You can find the proper procedure on threads here. Look it up in the search bar. Good luck

 

[sblanco]

Hi All
Thanks for all the input and suggestions. I have done some more testing and have found an erratic no spark on cyl#2. I used a spark tester at idle and found #2 would have spark and engine running smooth then it would stop sparking and of course engine ran with a miss. I swapped coils with a different cylinder and #2 still had an erratic spark. It would appear that I have an erratic signal to the coil from the CD box or a problem with the pickup or trigger from under the flywheel. How do I test further? Has anyone had such an erratic problem from the CD box? I had everything thing apart for the engine rebuild so maybe I installed something wrong, needs adjustment or something else with the trigger for CD box?
Please help if you can. Any info is greatly appreciated
Thanks
Scott

 

[puffitu]

Hi All
Thanks for all the input and suggestions. I have done some more testing and have found an erratic no spark on cyl#2. I used a spark tester at idle and found #2 would have spark and engine running smooth then it would stop sparking and of course engine ran with a miss. I swapped coils with a different cylinder and #2 still had an erratic spark. It would appear that I have an erratic signal to the coil from the CD box or a problem with the pickup or trigger from under the flywheel. How do I test further? Has anyone had such an erratic problem from the CD box? I had everything thing apart for the engine rebuild so maybe I installed something wrong, needs adjustment or something else with the trigger for CD box?
Please help if you can. Any info is greatly appreciated
Thanks
Scott

https://www.cdielectronics.com/wp-content/uploads/2013/02/CDI%20Troubleshooting%20Guide%20-%202012.pdf

maybe this will help; did wonders for my issues.

 

[sblanco]

Hi All
I should also mention that it would appear that I have 4 blue coils and 2 CD boxes in this system. Not sure what it’s called but I think it’s the older style system
Scott

 

[sblanco]

Thanks for the troubleshooting guide Puffitu
Scott

 

[puffitu]

Check all electrical components and do not omit the rectifier(easy to ohm check). Check the quick connect connections. There’s a way to ohm test the stator and trigger. Just read and study the troubleshooter guide-you may need to get a dva adapter and test it that way to isolate. There may be a broken/kinked wire somewhere you’re not seeing. Check all small electrical connections; give em all a pull test-sometimes they may look like they’re on good but may be visually deceiving and barely in the shrink tubing. You may have to replace the spark plug boots; I did and it cleared up some of my issues.

Thanks for the troubleshooting guide Puffitu
Scott

 

[jerryjerry05]

IF?? you suspect the pack??? then the only way to test is to swap the packs around and see if the no spark follows the pack.
The no fire on #2 is usually the stator or the trigger.
The trigger wires are very thin and can break under the shrinkwrap on the connector. I replace them all just in case??
The stator can test good and still be bad

 

[puffitu]

Shrink wrapping can be visually deceiving

 

[Poormansboating]

That it can be I replaced all my wires in my 85 and two new cdi boxes and it fires great now. Those wires are very brittle