Re: need help on a 86 125 force on a 19' bayliner capri
If my boat?
A - Check compression. Should be above 120 PSI (upper 140s - 150s is best) and within 10-15% variance from highest to lowest number.
B - Check spark on each individual plug. For this task, simply remove spark plug, use vise grips to clamp ground wire to its steel base, then get another person to turn the ignition key (to try and start the engine). As starter is cranking, look for deep blue spark on the removed plug. Yellow is weak spark. Repeat this step for each spark plug. Note: Even when quick testing, the spark plug base should always be grounded (or it might hurt its electronics). Simply pulling the plug's cap while idling might hurt its electronics as well. Thus, always best to ground the plug - for this test. If unknown history on its plugs, install new Spark Plugs as well.
C - Check gas flow. If idling rough, squeeze its primer bulb and if it revs up, then its fuel pump might be shot. If idling rough and its spitting gas out its carb, then its reed leafs might be shot. Check spark plug color as well. If color is off from each other, its one (or all) carbs might need cleaning or rebuild kits. If gas quality is unknown, use external tank (with fresh 50:1 mix gas). If existing gas filter quality / age is unknown, install new inline gas filter as well. Sometimes, all appears good but 1 x dirty carb can create same "no power under load / rough sounding" symptoms as well.
D - If timing was off (re: previous owner thought it was a idle adjustment - LOL!), it will make the engine sound good on muffs but have little power in the water. For this, one needs a timing light. At top of this Force Forum, there's a good video clip to check / adjust timing.
If all these items check out OK, I'd investigate its Prop size next. For this engine and size of boat. Prop size should be 17 or 19 Aluminum (depending on 3 or 4 blade and its average onboard weight loading). If previous owner installed a 21" Pitch (or higher size), it will "bog down" its engine as well (just like a standard vehicle starting from stop in 3rd gear.)
For now, start with the simple A (compression), B (spark) and C (gas flow) items. Then, move into the more advanced Timing and Prop Size confirmation areas.
Hope this helps.
