Hello all,
I am having probs with my motor not getting RPM's. Motor starts and idles fine but does not hit top RPM's at WOT. Periodically it will try to surge but just seems restricted. Compression test yielded 150 on one cylinder and 145 on the other. I don't have a tach, but it is pretty obvious that its not hitting top RPM's under load. The motor responds perfectly to the lever in neutral and revs high but bogs under load. I realize this is an old motor but it is very frustrating because it has run very well on ocassion but is very inconsistent. I do have the repair manual.
Here is what I have done and the results:
Changed plugs and gapped properly - Ran well for about 15-20 minutes but then RPM's died. Removed plugs and they were black and oily.
Replaced fuel pump and all fuel lines- no difference. In hindsight I shouldn't have replaced the pump but we just got the boat so throwing 70 bucks at it didn't seem to be a bad investment since the pump was original.
Took it to the shop and they replaced low speed packing (needles were backing out ) and adjusted - Ran well for about an hour but then RPM's died next trip out.
Decarbonized using sea foam and methods I found on IBoats and replaced pulugs - Did not change anything.
Took apart and cleaned and examined carbs without using new kits. (I know, I know) Everything looked clean and there were no blockages in the jets, orifices etc. - Made no differece in RPM's
In the next couple of days I am going to install new carb kits. I am hopeful but not confident this is the issue. If there were restrictions in the carbs it would seem to me that it would never hit high rpm's and this motor has on occasion. Seems to get worse the longer it runs.
I have also noticed some hairline cracks in the ignition coils. I have read that the coils can fail at high temp so my question is: If I buy an inline spark tester will I get a false positive on the muffs because the coils are not hot enough to fail? I don't really want to try the inline tester in the water if I can avoid it. How long can I run the motor on muffs to allow the coils to heat up?
Also, could this be a cooling issue?
Any other advice would be appreciated.
I am having probs with my motor not getting RPM's. Motor starts and idles fine but does not hit top RPM's at WOT. Periodically it will try to surge but just seems restricted. Compression test yielded 150 on one cylinder and 145 on the other. I don't have a tach, but it is pretty obvious that its not hitting top RPM's under load. The motor responds perfectly to the lever in neutral and revs high but bogs under load. I realize this is an old motor but it is very frustrating because it has run very well on ocassion but is very inconsistent. I do have the repair manual.
Here is what I have done and the results:
Changed plugs and gapped properly - Ran well for about 15-20 minutes but then RPM's died. Removed plugs and they were black and oily.
Replaced fuel pump and all fuel lines- no difference. In hindsight I shouldn't have replaced the pump but we just got the boat so throwing 70 bucks at it didn't seem to be a bad investment since the pump was original.
Took it to the shop and they replaced low speed packing (needles were backing out ) and adjusted - Ran well for about an hour but then RPM's died next trip out.
Decarbonized using sea foam and methods I found on IBoats and replaced pulugs - Did not change anything.
Took apart and cleaned and examined carbs without using new kits. (I know, I know) Everything looked clean and there were no blockages in the jets, orifices etc. - Made no differece in RPM's
In the next couple of days I am going to install new carb kits. I am hopeful but not confident this is the issue. If there were restrictions in the carbs it would seem to me that it would never hit high rpm's and this motor has on occasion. Seems to get worse the longer it runs.
I have also noticed some hairline cracks in the ignition coils. I have read that the coils can fail at high temp so my question is: If I buy an inline spark tester will I get a false positive on the muffs because the coils are not hot enough to fail? I don't really want to try the inline tester in the water if I can avoid it. How long can I run the motor on muffs to allow the coils to heat up?
Also, could this be a cooling issue?
Any other advice would be appreciated.
