Northern Lights M20CRW3, Operator'S Manual

OM844W3  11/13

24

Servicing

2. Here are acceptable water quality specifications:

3.  If chlorides, sulfates or total dissolved solids are 

higher than the above given specification, the water 

must be distilled, demineralized, or 

  deionized before it is used in a cooling system.

4.  If total hardness is higher than 170 ppm and all other 

parameters are within the given 

  specifications, the water must be softened before it is 

used to make coolant solution.

SP13.  CHECK THE COOLANT LEVEL

1.  Check the coolant level each day before starting the 

engine. Check the water level by removing the 

  pressure cap from the expansion tank. 

  In order to give the cooling water an opportunity to 

expand, the level should be about 1 in. (2.5 cm) below 

the filler cap sealing surface when the engine is cold.

2.  The pressure valve in the filler cap releases when the 

pressure is approximately 7 PSI (0.5 bar). Use a cap 

pressure tester to check cap if you suspect it is faulty.

SP14.  COOLING SYSTEM FLUSHING

1.  Flush the cooling system every 2500 hours. 

2.  Marine sets:

  a.  Remove expansion tank cap and drain engine 

   block.

  b.  Open block drain cock. Remove hose from 

    bottom of heat exchanger tank.

  c.  Pour clean water into expansion tank until water 

    coming from drains is free of discoloration and 

    sediment. Let water drain completely. Close 

    drains and refill with recommended mixture.

3.  Coolant Specifications:

  Use 50% distilled water / 50% ethylene glycol 

  antifreeze mix. Antifreeze mixture is recommended

  as a good year-round coolant.

4.  Check hoses and connections and repair any leak-

age.

SP15.  HEAT EXCHANGER 

1.  Clean the heat exchanger core after 2500 hours of 

operation.

2.  Drain expansion tank and heat exchanger.

3.  Remove heat exchanger end covers and remove 

core.

4.  Clean the inside of exchanger core tubes using 

  a metal rod. Flush, inspect and clean again if 

 necessary.

5.  Reassemble. Fill the cooling system, start the engine 

and check for leaks.

SP17.  RAW WATER PUMP 

1.  Change the seawater pump impeller every 1000 

hours, or as needed.

2.  Remove the pump end cover.  Pry out the impeller 

using needle-nose pliers or two screwdrivers. 

  Be sure you remove all pieces of failed impeller.

  NOTE:  Place some kind of protection under the 

screwdrivers in order not to damage the pump 

housing. If the impeller has broken into pieces, 

remove front heat exchanger end cover and inspect 

for impeller pieces. Clean inlet to heat exchanger 

bundle and reassemble.

3.  Clean the inside of the housing.

4.  Press in the new impeller and place the sealing 

washers in the outer end of the impeller center if this 

has not already been done.

5.  Replace the cover using a new gasket.

NOTE:  Make sure that there is always an extra 

impeller and cover gasket in reserve on board.

GENERATOR ENDS

  The maintenance and operation recommendations 

for the generator end are in a separate Owner’s 

Manual. If you do not have one of these manuals, 

contact your local Northern Lights dealer.

ELECTRICAL SYSTEM - GENERAL

1.  Never switch battery switch off or break the circuit 

between the alternator and batteries while the engine 

is running. Regulator damage can result.

Parts Grains

Contaminates 

per Million  per Gallon

Maximum Chlorides 

40 

2.5

Maximum Sulfates 

100 

5.9

Maximum Dissolved Solids 

340 

20.0

Maximum Total Hardness 

170 

10.0

PH Level 5.5 to 9.0

revised 11-8-13