Ok, here is the back story; 1987 Sea Ray with 2.3L OMC Cobra.
Observations; Starts fine, idles well in neutral dockside. Underway at an idle there is a small, almost unnoticeable at first, misfire or stumble that occurs randomly. The severity of it grows the longer the engine is running but does not grow to the point I start to wonder if paddles are still stowed in the bilge compartment or the tow rope is still under the seat (we have kids around here so?you understand
) for at least 30-40 minutes. When I cob on the power to make the wind blow through the little miss?s hair, the power delivery is also random. If I try to plane out shortly after leaving dockside she pops out of the water like she?s on a mission. If after some time of operation (slow or fast) I try to cob on the power the misfire or stumble is exaggerated and power is so low that I can hardly plane her out without putting ballast in the nose (yep trimmed all the way down). This situation seems to get worse with time during a cruise but is alleviated somewhat if I let the boat sit for a while like while swimming at the sandbar.
Gas is confirmed good. Carb rebuilt last week, float settings double checked. Have found no vacuum leaks. Points are clean and gapped correctly. Cap and rotor inspected with no findings. Timing is on spec. Plugs are clean but appear leaner than I care to see them. Plug wires are new within 18 months / 20 operational hours. I even disconnected the ESA switch to see if it was intermittently causing this issue but the same indications are present. ESA switch has since been reconnected. Vacuum and compression checks on the list of things to do.
So at this point are you thinking a fuel related problem related to heat build up? Ok, I can follow that idea for a minute but the cooling system on this thing is phenomenal. It runs to the cool side under light loading, 140 and 170 when run hard as read on the dash mounted temperature indicator. I believe these indications because when the engine cowling is removed the engine is cooler to the touch than the V8 in my 68 GTO. This takes the vapor lock scenario off the plate for me.
Ok, here is what I am thinking but I don?t know how to confirm or deny it. I think the power valve in the carb is somehow not actuating. This problem started to show itself last year and I was all over the carb as a root cause so we cleaned and rebuilt it. The only thing I did not do was remove the power valve because it is ?staked? into the carb housing and I was not sure how to remove the staking without?causing damage.
I do have, thanks to other iboat forum members, a theory that is starting to evolve around a water leak that is somehow getting into the combustion chamber?ok, no I am not smoking crack, I just have this idea: Is there any merit to it? Oil is clean but quantity is on the high side. Read something about that some where; should I draw the excess out?
What are your thoughts?
Raymond
Observations; Starts fine, idles well in neutral dockside. Underway at an idle there is a small, almost unnoticeable at first, misfire or stumble that occurs randomly. The severity of it grows the longer the engine is running but does not grow to the point I start to wonder if paddles are still stowed in the bilge compartment or the tow rope is still under the seat (we have kids around here so?you understand
) for at least 30-40 minutes. When I cob on the power to make the wind blow through the little miss?s hair, the power delivery is also random. If I try to plane out shortly after leaving dockside she pops out of the water like she?s on a mission. If after some time of operation (slow or fast) I try to cob on the power the misfire or stumble is exaggerated and power is so low that I can hardly plane her out without putting ballast in the nose (yep trimmed all the way down). This situation seems to get worse with time during a cruise but is alleviated somewhat if I let the boat sit for a while like while swimming at the sandbar.Gas is confirmed good. Carb rebuilt last week, float settings double checked. Have found no vacuum leaks. Points are clean and gapped correctly. Cap and rotor inspected with no findings. Timing is on spec. Plugs are clean but appear leaner than I care to see them. Plug wires are new within 18 months / 20 operational hours. I even disconnected the ESA switch to see if it was intermittently causing this issue but the same indications are present. ESA switch has since been reconnected. Vacuum and compression checks on the list of things to do.
So at this point are you thinking a fuel related problem related to heat build up? Ok, I can follow that idea for a minute but the cooling system on this thing is phenomenal. It runs to the cool side under light loading, 140 and 170 when run hard as read on the dash mounted temperature indicator. I believe these indications because when the engine cowling is removed the engine is cooler to the touch than the V8 in my 68 GTO. This takes the vapor lock scenario off the plate for me.
Ok, here is what I am thinking but I don?t know how to confirm or deny it. I think the power valve in the carb is somehow not actuating. This problem started to show itself last year and I was all over the carb as a root cause so we cleaned and rebuilt it. The only thing I did not do was remove the power valve because it is ?staked? into the carb housing and I was not sure how to remove the staking without?causing damage.
I do have, thanks to other iboat forum members, a theory that is starting to evolve around a water leak that is somehow getting into the combustion chamber?ok, no I am not smoking crack, I just have this idea: Is there any merit to it? Oil is clean but quantity is on the high side. Read something about that some where; should I draw the excess out?
What are your thoughts?
Raymond