Re: force 125hp serie c 1988
You are describing such a general problem that you must start from scratch and diagnose the problem. SO: since the ignition system is the most trouble prone system, start there. The first and easiest thing to do would be to remove each sparkplug one at a time and while cranking the engine see if there is a good hot blue spark at each plug. If there is not, then you have a problem with the ignition system,
If you have a strong spark on all plugs, then the next simplest test is to check the compression of each cylinder. It should be well over 100 PSI on each cylinder. If one is very low, like 20 or 60 PSI, then you know the problem is there.
If there is good compression on all cylinders and strong spark, then the next thing to check is the fuel system. See if the carbs are openinmg all the way. See if the fuel pump is delivering sufficient fuel. See if the priming bulb collapses while running the engine, indicating a clog in the fuel line.
Hopefully these simple tests will narrow down the choices of what the problem is.