Herb,
My diesel book ("Troubleshooting Marine Diesels", Peter Compton) says that if the rpms get within 10 percent of expected, the most likely cause is overloading.
In order of likelihood: dirty prop, dirty bottom, prop shaft binding, wrong prop, wrong transmission ratio.
Or the cause may be poor fuel supply, in order of likelihood: injector defective, air in system, contaminated fuel, water in fuel, control cable restricted, extra washer under injector, injector pipes leaking, lift pump defective, injector pump contaminated, fuel tank vent restricted,
With dark exhaust smoke: restricted air intake, restricted exhaust
Personally, when I run into the problem of something falling ten percent short of expected, I have learned to do nothing for a while. I learned it from my wife, who says it is why we are still married.
My diesel book ("Troubleshooting Marine Diesels", Peter Compton) says that if the rpms get within 10 percent of expected, the most likely cause is overloading.
In order of likelihood: dirty prop, dirty bottom, prop shaft binding, wrong prop, wrong transmission ratio.
Or the cause may be poor fuel supply, in order of likelihood: injector defective, air in system, contaminated fuel, water in fuel, control cable restricted, extra washer under injector, injector pipes leaking, lift pump defective, injector pump contaminated, fuel tank vent restricted,
With dark exhaust smoke: restricted air intake, restricted exhaust
Personally, when I run into the problem of something falling ten percent short of expected, I have learned to do nothing for a while. I learned it from my wife, who says it is why we are still married.