l have been looking into this issue for two seasons and still have not been able to resolved it.
A little background: I have a 1983 hunter 34 powered by a yanmar 3GMF Diesel 25 Hp and I am the original owner. It is now 38 years old and all original. Engine is in excellent condition and has been well maintained over the years. No engine hour gauge but I estimate engine hours to be approximately 3000 - 3800 hrs.
Fuel pump and injectors replaced 2003, all regular routine yearly engine maintenance done, fuel/oil filters changed, fuel inspected and stabilized etc. replace mixing elbow 4 years ago, and throttle cable replace two years ago.
Engine runs absolutely perfectly, starts on the fist crank, no smoke, excellent water flow, no issues at all except the rpm issue under load. The fuel filters both have less then 20 hours on them and have always been clean.
Normally I would be able to reach hull speed of 7 - 7.5 knots any time of the season at full throttle and now 5.5 - 6.2 knots with no wind or current. Every season the boat is hauled no barnacles and very little slime if any. Prop is the same I have had for thirty years and always clean.
No apparent fuel issues, engine doesn’t appear to be starved of fuel and tank was emptied and new diesel added to rule out bad fuel. Manually able to engage the throttle to max throttle and cable appears to be functioning properly. Just cannot throttle up past 2200 rpm.
I read that the tech gauge on these boats are problematic and sometimes inaccurate however if this is an instrumentation issue then ground speed would not be effected.
Other post have reported rpms of 3200 - 3800 and ground speeds of 7.5 knots which is about what I remember it normally running at.
any suggestions would be appreciated.
A little background: I have a 1983 hunter 34 powered by a yanmar 3GMF Diesel 25 Hp and I am the original owner. It is now 38 years old and all original. Engine is in excellent condition and has been well maintained over the years. No engine hour gauge but I estimate engine hours to be approximately 3000 - 3800 hrs.
Fuel pump and injectors replaced 2003, all regular routine yearly engine maintenance done, fuel/oil filters changed, fuel inspected and stabilized etc. replace mixing elbow 4 years ago, and throttle cable replace two years ago.
Engine runs absolutely perfectly, starts on the fist crank, no smoke, excellent water flow, no issues at all except the rpm issue under load. The fuel filters both have less then 20 hours on them and have always been clean.
Normally I would be able to reach hull speed of 7 - 7.5 knots any time of the season at full throttle and now 5.5 - 6.2 knots with no wind or current. Every season the boat is hauled no barnacles and very little slime if any. Prop is the same I have had for thirty years and always clean.
No apparent fuel issues, engine doesn’t appear to be starved of fuel and tank was emptied and new diesel added to rule out bad fuel. Manually able to engage the throttle to max throttle and cable appears to be functioning properly. Just cannot throttle up past 2200 rpm.
I read that the tech gauge on these boats are problematic and sometimes inaccurate however if this is an instrumentation issue then ground speed would not be effected.
Other post have reported rpms of 3200 - 3800 and ground speeds of 7.5 knots which is about what I remember it normally running at.
any suggestions would be appreciated.