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YACHTS AND LAUNCHES WITH HEAT EXCHANGER COOLING
It is essential that a solution of fresh water and anti-freeze is
used as engine coolant. The amount of anti-freeze must be
between 33% to 50%. This not only stops 'freezing up' in
winter, but it prevents overheating and corrosion.
The warranty is invalid unless the correct ratio is used.
The concentration of ethylene must NOT exceed 50%.
SEA WATER PUMP AND COOLING SYSTEM
IMPORTANT!
Before working on the sea water system ensure that the
sea cock is in the off position!
1. It is very important that the correct sea water flow is
maintained to cool the closed circuit system of the
engine. The key component in this system is the sea
water pump impeller. This should be checked every
year by removing the circular plate. See photo 44.
2. Withdraw the rubber impeller from its drive shaft as
shown. See photo 45.
44
The anti-freeze in the fresh water system enables the boiling
point of water to rise to 124°C with a 13 psi pressure cap
fitted.
The water temperature alarm switch will however be
activated at 95°C to 100°C. If no anti-freeze or a very weak
solution is used, then the water temperature switch may not
be activated before coolant is lost.
3. Check impeller for cracks in the rubber, excessive
wear or lost vanes. Replace with a new impeller as
necessary.
Note: If any pieces of rubber impeller are missing then
they must be found as they are most likely to be trapped
in the entrance to the heat exchanger cooling stack.
See 'Cleaning Tube Stack'.
4. Re-assemble using new 'O' rings. Do not over tighten
end cap bolts and make sure the tube stack is the
right way round for end cap location.
5. Re-fill engine with coolant (water/anti-freeze solution)
and run engine up to temperature to check for leaks.
45
37
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