Ill get right to it.
1974? Mercury 650 3 cyl 2 carb
Was running great in Puget Sound yesterday and lost 1/3 of its power. Was missing badly on that cylinder after that. Got it home and SEEMED to be running fine on the hose (i bet it wasn't but whatever). Took it out to the lake today for 4th festivities...only running on top 2 cylinders. Cant get the 3rd to fire at all.
Trouble shooting so far
-cylinder IS getting spark...removing the plug and running the engine with plug up against block has big white/blue spark
-cylinder does have compression (compression tester is 115 top 115 middle 100 bottom. Yes the bottom cyl is lower than the rest. I know that's not good but is that enough for it to not fire at all? It ran perfectly up until it didn't and I have a hard time believing it went from 100% fire to 0% fire by just getting wore out.
Boat runs fine on top 2 cylinders whether the bottom plug is connected to plug wire or not. Connecting or disconnecting the wire changes nothing.
Next things to check?
Its summer and the cost of outboards up here is terrible. I had a good running Johnson that I got rid of for this Mercury thinking it was the right move. Now I'm very upset with my decision. Hope its not a fatal issue.
Rob
Maple Valley WA
1974? Mercury 650 3 cyl 2 carb
Was running great in Puget Sound yesterday and lost 1/3 of its power. Was missing badly on that cylinder after that. Got it home and SEEMED to be running fine on the hose (i bet it wasn't but whatever). Took it out to the lake today for 4th festivities...only running on top 2 cylinders. Cant get the 3rd to fire at all.
Trouble shooting so far
-cylinder IS getting spark...removing the plug and running the engine with plug up against block has big white/blue spark
-cylinder does have compression (compression tester is 115 top 115 middle 100 bottom. Yes the bottom cyl is lower than the rest. I know that's not good but is that enough for it to not fire at all? It ran perfectly up until it didn't and I have a hard time believing it went from 100% fire to 0% fire by just getting wore out.
Boat runs fine on top 2 cylinders whether the bottom plug is connected to plug wire or not. Connecting or disconnecting the wire changes nothing.
Next things to check?
Its summer and the cost of outboards up here is terrible. I had a good running Johnson that I got rid of for this Mercury thinking it was the right move. Now I'm very upset with my decision. Hope its not a fatal issue.
Rob
Maple Valley WA