Gearbox issue?

[Ken13559]

Yanmar 2GM20F with KM2P gearbox and Kiwiprop.
Occasional after driving forward, when I throttle to reverse my engine felt loaded with black smoke and rpm won't rise. Then I neutral and forward it then neutral and reverse again and reserving is normal like nothing happened.
Checked prop no issue. Blades feathered easily.
So what gives?
I suspect there's damage in my gearbox.
Anyone had similar experiences?

 

[Benny17441]

Black smoke is a result of over fueling. The governor system responds to loads placed on the engine and transferred from the prop. The governor allows more fuel flow as the load on the engine increases. Under certain conditions the parameters of the governor are fooled into delivering more fuel than necessary 1) the boat is moving forward or strong current while the prop is moving in opposite direction, 2) fouled prop 3) poor compression or condition of the injectors 4) mechanical resistance of shaft or transmission 5) components wear of the governor system and injection timing off 6) excessive marine growth on the hull. Your expressed condition does not merit at this time to start fooling with the governor or high pressure injector pump timing. Spin the shaft by hand in both directions to make sure there is no mechanical excess friction. With engine running listen for irregular noises in the transmission as the shift lever is moved at the transmission. Insure the linkage system to the transmission is properly adjusted and the same with the throttle control. Tune the engine up, replacing filters and adjusting valve lash. It is very hard to diagnose online but hope some of these comments help.

 

[Ralph Johnstone]

Occasional after driving forward, when I throttle to reverse my engine felt loaded with black smoke and rpm won't rise.

The prop was immediately my first thought and then you blew it out of the water with your next statement about no prop issues.

Checked prop no issue. Blades feathered easily.

I still say it's something in the prop which you are just not seeing at the time you are inspecting the prop. Somehow it manages to jam with the blades positioned 90° to the rotation of the shaft. That would REALLY make it hard for the shaft to turn with loads of smoke thrown into the equation.

Good luck with the hunt.

 

[knackers]

had the same problem with my kiwi prop, one of the reversing rollers had fallen out, no reverse and struggling to get revs

 

[Ken13559]

had the same problem with my kiwi prop, one of the reversing rollers had fallen out, no reverse and struggling to get revs

Hmmmm.... haven't serviced my Kiwiprop since bought new several years ago.
Serbici6it is always on my mind but somehow on back burner.....

 

[Ken13559]

Black smoke is a result of over fueling. The governor system responds to loads placed on the engine and transferred from the prop. The governor allows more fuel flow as the load on the engine increases. Under certain conditions the parameters of the governor are fooled into delivering more fuel than necessary 1) the boat is moving forward or strong current while the prop is moving in opposite direction, 2) fouled prop 3) poor compression or condition of the injectors 4) mechanical resistance of shaft or transmission 5) components wear of the governor system and injection timing off 6) excessive marine growth on the hull. Your expressed condition does not merit at this time to start fooling with the governor or high pressure injector pump timing. Spin the shaft by hand in both directions to make sure there is no mechanical excess friction. With engine running listen for irregular noises in the transmission as the shift lever is moved at the transmission. Insure the linkage system to the transmission is properly adjusted and the same with the throttle control. Tune the engine up, replacing filters and adjusting valve lash. It is very hard to diagnose online but hope some of these comments help.

I'll need to work thru this laundry list