Re: At The Lake NOW and need help '72 Merc 115HP
How long is the boat and what type?
What's the pitch on the prop?
If you're trying to push a heavy boat with a prop with too much pitch, it's not gonna go.
Will it actually idle smoothly in gear without dying? If you can get it to do this OK, likely all the cyl's are firing.
To confirm this, block the throat of one carb with your hand or a stout shop rag while the engine's running. If that carb & its cyl's are carrying the load, the engine rpm will fall drastically. If rpm only falls off a little or none at all, you've got problems with one or both cyl's associated with that carb.
Repeat for all 3 carbs.
Something else to try, if you're Real Real careful, is a cylinder "drop test". With the motor idling in Neutral (too dangerous to try this in gear!), pull one plug wire at a time. Note, make sure your hands are dry and you're either using a well-insulated pair of pliers, or something like a long screwdriver that you can use to pry the plug wire off the spark plug, or there'll be a nasty Zap involved!!
Before starting you could even pull the plug wire slightly away from the plug and it'll be easier to remove, but will still spark the plug. BTW if the plug boots are lightly lubed with silicone dielectric grease, they'll slide off a lot easier.
If the engine rpm falls when you pull the plug wire, you know that cyl's OK. From what I recall, if the rpm Rises, you could have a warped exhaust baffle. But I expect that's kinda rare.
BTW, what happens if you were to momentarily hit the choke button when you're trying to plane-out the boat, does that cause stalling or does it run better?
Ign wise, check spark plug wires at night for a "fireworks show". If you see a lot of glowing, the wires are shot.
Pull the distributor cap (just a screw/nut on the clamp that holds it in place) and see if there's a lot of debris/crud. If it looks real nasty in there, get a can of carb cleaner and spray the heck out of it.
To keep the mess down, let the effluent run out onto a rag. You can literally flush the cap clean this way. Be sure the carb cleaner has completely evaporated before reassembly.
Make sure the center, spring-loaded carbon contact in the cap is free to move in/out, if not take it out, clean and reinstall.
Ensure the contact is well-inserted in-place, otherwise it'll spring out and you may break it when putting the cap on.
That's all I got, but I expect something in this grocery list is gonna give you a clue as to what's going on.
HTH & G'luck............ed
