telstar_2112
New member
"We have a 92 Yamaha ProV 175
"We have a 92 Yamaha ProV 175 on a 21' Grady. Ran fine for years. Suddenly it lacked the power to get up on plane. So the investigation started:
Compression is good on all cylinders, 115-125.
We pulled each plug wire off under load and found that the bottom left cylinder is not contributing. All others had a noticeable slowdown and speed up as we pulled the wires off and put them back on.
We checked that the plug was firing, it was, but we tried replacing it any how. No-change.
Swapped coils, no change. Same cylinder bad.
Note, that one plug from the bad cylinder was shinny and spotless clean like new, while the other 5 were a little dark and a little oily. (they are relatively new as well since we replace them two weeks ago and only ran a little bit.)
Removed that carburator and took out all jets and pretty much any brass parts and although they looked spotless clean, blew them out with carb cleaner. All ports seemed to blow through. Ran it again and no change, cylinder still not contributing.
Checked that that float bowl on that carb was full of gas, it was. Cleaned carb again, out of desperation, no change.
Clear bowl on engine always had plenty of fuel in it and other 5 cylinders run fine.
I have pretty much used up my limited knowledge of boat engines so if anyone has any suggestions, please, please help!
TIA,
Steve."
"We have a 92 Yamaha ProV 175 on a 21' Grady. Ran fine for years. Suddenly it lacked the power to get up on plane. So the investigation started:
Compression is good on all cylinders, 115-125.
We pulled each plug wire off under load and found that the bottom left cylinder is not contributing. All others had a noticeable slowdown and speed up as we pulled the wires off and put them back on.
We checked that the plug was firing, it was, but we tried replacing it any how. No-change.
Swapped coils, no change. Same cylinder bad.
Note, that one plug from the bad cylinder was shinny and spotless clean like new, while the other 5 were a little dark and a little oily. (they are relatively new as well since we replace them two weeks ago and only ran a little bit.)
Removed that carburator and took out all jets and pretty much any brass parts and although they looked spotless clean, blew them out with carb cleaner. All ports seemed to blow through. Ran it again and no change, cylinder still not contributing.
Checked that that float bowl on that carb was full of gas, it was. Cleaned carb again, out of desperation, no change.
Clear bowl on engine always had plenty of fuel in it and other 5 cylinders run fine.
I have pretty much used up my limited knowledge of boat engines so if anyone has any suggestions, please, please help!
TIA,
Steve."