carb, or ignition? dilema

[tommix]

1986 25hp mariner,idles well. at mid and full throtle runs well.problem at low throtle just progressing to move forward engine chuggs and runs like there something preventing clean smooth firing equally on both cylinders . i have replaced all gaskets in carb, fuel pump, float, adj, and low speed adj plugs and wires dont help.local johnston marina suggested i visit mercury marina as they said :eliminate switch box! . if my problem is ignition what percentage would be suspect of stator, trigger,switch box,coils to plugs . (engine compression good on both cylinders) any suggestions truly apreciated .

 

[Laddies]

Re: carb, or ignition? dilema

It sounds like the syncronization is off

 

[hkeiner]

Re: carb, or ignition? dilema

If my problem is ignition what percentage would be suspect of stator, trigger,switch box,coils to plugs . (engine compression good on both cylinders) any suggestions truly appreciated .

I think that it is generally recommended to test/troubleshoot ignition system components rather than just replace ignition parts randomly (or based upon an educated guess or probability) to try to fix a problem. A shop manual for your motor should describe many of the troubleshooting steps applicable for your ignition system. I feel it is much cheaper in the long run to get an ohmmeter and DVA meter and perform the various tests before replacing ignition parts that may or may not be defective.

When I first got my used motor last year I had poor idling/acceleration symptoms and suspected failed ignition component(s). I did all the shop manual's troubleshooting tests of the ignition system. I also got a SmarTach TA100 for myself, which let me directly monitor the secondary voltage on each spark plug wire during idle and acceleration. These tests showed me that nothing was apparently wrong with the ignition. This saved me the expense of unnecessarily replacing good ignition components and got me to focus my attention instead on to other possible causes. This is my experience anyways.

For troubleshooting non-ignition problems (and there are many possibilities), following the excellent advice you get on this forum (such a performing a link and sync) is a very good way to go. Following such advice has helped me a lot in the past.