Changing The Raw Water Impeller; Heat Exchanger; Zinc Anode - Universal M3-20A Operator's Manual

ENGINE COOLING CIRCUIT
Changing the Raw Water Impeller
1. Close the raw water intake,
2. Remove the inlet and outlet
rx>rt
hoses from the pump,
noting the port location and positioning.
3. Remove the pump assembly and its gasket from the
engine.
4. Remove the three hex head screws that hold the housing
to the cover.
5. Tap the housing/cover assembly on its side to loosen and
separate the cover from its housing.
6. Remove the cover and its O-ring and remove the impeller
gasket and plate.
7. Remove the retaining ring (circ1ip) and pry out the
impeller. Take care not to lose the key off the shaft's key-
way.
ACAUTION:
If any of the vanes have broken off the
impeller they must be found to prevent blockage in the
cooling circuit. They often can be found in the heat
exchanger.
8. Replace the gasket, impeller, and O-ring.
9. Apply a film of petroleum jelly or silicone to the inner
surface of the impeller housing.
NOTE:
Just coat the surface, do not over apply.
10. Install the cover housing over impeller.
11. Install the three hex screws and tighten.
15
12. Mount the pump to the engine taking care thai the end
seal and gasket are in place. Do not tighten the pump
mounting screws, just finger tight.
13. Rca<;semhlc the hose connections and open the raw
water intake.
14. Start the engine in idle, this will allow the pump to align
itself with its drive shaft.
15. Stop the engine and tighten the pump assembly mount-
ing screws.
16. Start and run the engine, check for leaks and check for a
norrnal operating temperature.
NOTE:
Should a failure occur with the pumps internal parts
(seals and bearings)
it
may be more cost efficient to purchase
a new pump. The price of individual parts would almost
match the price of a new pump.
Heat Exchanger
The heat exchanger is a copper tUhe which encloses a num-
ber of small copper tubes. Raw water is pumped through the
small copper tubes and the freshwater coolant from the
engine is circulated around the copper tubes. The raw water
removes heat from the freshwater coolant. To keep the heat
exchanger operating efficiently, it should be removed from
the engine every 1000 hours to be thoroughly cleaned and
pressure tested.
HEAT EXCHANGER
O-RING
Zinc Anode
CLEAR OUT
DEBRIS
DRAIN
POOR
ZINC ANODE
i
A zinc anode or pencil, is located in the raw water cooling cir-
cuit within the heat exchanger. The purpose of the zinc anode
is to sacrifice itself to electrolysis action taking place in the
raw water cooling circuit, therehy reducing the effects of elec-
trolysis on other components of the system. The condition of
the zinc anode should be checked monthly and the anode
cleaned or replaced, a<; required. Spare anodes should he car-
ried onboard. The area in the exchanger where the anode is
located should periodically he cleaned of anode dehris.