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Hurth Hydraulic Transmission
The following Trouble location chart is intended as a basic guideline for the trans itself. Considerations such as engine and hull condition, as well as prop and shaft condition need to be evaluated first. Always try to shift the unit at the trans (disconnect the shift cable) to evaluate hard shifting, as it is usually caused by the cable to the trans and not the trans itself...
1. Transmission gears cannot be shifted
A. Shifting lever loose. Tighten clamping screw on shifting lever
B. Remote control does not permit lever travel required for testing
Lift remote control off, if gears can be shifted by hand,
correct remote control
C. Remote control faulty. Repair remote control
D. No shifting pressure available. Refer to 7
2. Gears are shifted sluggishly
Lever travel of remote control is too short;
lever shift just short of minimum traveling distance.
Lift remote control off, if gears can be shifted by hand,
correct remote control
3. Clutch is slipping; propeller speed too low as compared to engine speed
A. Incorrect fluid used
Drain and refill with correct fluid,
flush transmission while engine runs
in neutral position, drain fluid, refill
transmission.
B. Fluid contains water Refer to 9
C. Shifting pressure too low Refer to 6
D. Wear on clutch discs
Disassemble transmission replace clutch discs
E. Piston rings in clutch are damaged
Disassemble transmission, replace clutch
4. Transmission is blocked
A. Medium piston ring in input shaft in control block is faulty
Remove control block, replace piston ring,
replace control block if worn.
5. Output shaft turns in neutral position
A. Rotary slide valve in control block is worn
Replace control block
B. Faulty needle bearing on input shaft
Disassemble transmission and
input shaft, replace bearing
C. Dished discs due to overheating of slipping clutch
Refer to 3
6. Shifting pressure too low
A. Fluid filter dirty
Replace fluid filter
B. Fluid level in transmission is too low
Fill with fluid; check for fluid loss
in transmission, cooler and pipelines
lines for leaks also refer to steps 10 to 13
C. Fluid pump is worn out
Replace control block together with fluid pump
D. Piston rings in input shaft in control block are faulty
Remove control block and replace piston
rings. also replace control block
E. Piston rings in clutch are faulty
Disassemble transmission, replace clutch
7. No shifting pressure
A. Direction of engine rotation does not agree
with arrow on transmission
Replace with L.H. rotation engine
B. No fluid in transmission
Refill with fluid
C. Fluid filter is dirty
Replace fluid filter
D. Fluid level in transmission is too low
Fill with fluid; check for fluid
loss in transmission, cooler and
pipelines lines for leaks also
refer to steps 10 to 13
E. Fluid pump is worn out
Replace control block together with fluid pump
F. Fitting key in input shaft for fluid pump drive is broken
Remove control block. Replace fitting key
and any other faulty parts
G. Shifting pressure relief valve spring is broken
Replace control block
8. Excessive fluid temperature
A. Excessive fluid in transmission
Remove excessive fluid with commercial fluid pump
B. Fluid cooler is dirty on water side
Remove coolant lines and clean fluid
cooler on water side.
C. Worn fluid pump in control block
Replace control block and fluid pump
D. Faulty piston rings in input shaft in control block
Remove control block, replace piston rings
in input shaft. Check control block and
replace if damaged from faulty piston rings.
E. Clutch is slipping Refer to 3
F. Clutch does not open completely due to worn clutch discs
Dismount transmission, replace inner disc and
all faulty parts.
G. Clutch does not open completely due to broken clutch cup
springs. Disassemble transmission, replace inner disc
support and/or clutch
H. Low water flow from sea pump
repair or replace sea pump
9. Water in fluid, fluid looks milky
A. Fluid cooler faulty
Repair leakage at cooler or
replace cooler.
B. high water level in engine compartment, water
entering at output shaft seal
Remedy cause for water level in engine compartment,
change transmission fluid
10. Fluid leakage at input shaft
A. Breather clogged by paint or dirt
Remove dirt or paint from breather.
B. Shaft seal faulty
Disassemble transmission, replace seal.
If seal location on input shaft is
worn repair surface
11. Fluid leakage at output shaft
A. Breather clogged by paint or dirt
Remove dirt or paint from breather
B. Shaft seal faulty
Disassemble transmission, replace seal.
If seal location on input shaft is worn
repair shaft surface
12. Fluid leakage at venting filter
A. Excessive fluid in transmission
Pump out excessive fluid with commercial hand pump
13. Fluid leakage at joints or screw connections
A. Bolts are not tight
Tighten bolts to specified torque
B. Seals on bolts have been reused several times
Replace seals, tighten bolts to specified torque
14. Fluid leakage at filter cap or breather
A. Filter cap not flush or tight
Reinstall filter cap flush with
housing and tighten
B. Filter cap o-ring damaged
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