MerCruiser 13, Service Manual

Page: 315 / 348

CLOSED COOLED MODELS - 6B - 5 90-816462 2-695
2. Remove closed cooling circuit hoses and inspect
the tubes just inside the nipples. Because the
complete exchanger cannot be inspected, the
heat exchanger should be replaced if blockage is
suspected.
Testing Pressure Cap
Pressure cap is designed to maintain a pressure of
approximately its rated capacity (refer to “Specifica-
tions”) in closed cooling section once engine has at-
tained operating temperature. Cap should be
cleaned, inspected and pressure-tested at regular
tune-up intervals or whenever cap is suspected of
maintaining improper pressure as follows:
! WARNING
Allow engine to cool before removing pressure
cap. Sudden loss of pressure could cause hot
coolant to boil and discharge violently. After en-
gine has cooled, turn cap 1/4 turn to allow any
pressure to escape slowly, then push down and
turn cap all the way off.
1. Carefully remove pressure cap from reservoir or
heat exchanger.
2. Wash cap with clean water to remove any depos-
its or debris from sealing surfaces.
3. Inspect gasket (if used) and rubber seal on cap for
tears, cuts, cracks or other signs of deterioration.
Replace gasket, if damaged, or entire cap if rub-
ber seal is damaged.
72714
b
c
a
a - Rubber Seal (Cap MUST BE Replaced if Damaged)
b - Gasket (Look for Cracks under Gasket)
c - Locking Tabs (1 Hidden)
4. Check that locking tabs on cap are not bent or
damaged.
5. Using a cooling system pressure tester (similar to
one shown), test cap to be sure that it releases at
proper pressure and does not leak. (Refer to in-
structions which accompany tester for correct test
procedure.) Cap must relieve pressure at 14 PSI
(97 kPa), and must hold rated pressure for 30 se-
conds without going below 11 PSI. Replace cap
if it fails to fall within these limits.
72716
IMPORTANT: Before reinstalling cap in next step,
examine lower inside sealing surface in filler
neck to ensure that it is perfectly smooth and free
of debris. Also, inspect cam lock flanges on sides
of filler neck to be sure that they are not bent.
72715
b
a
a - Inspect for Damage
b - Cam Lock Flange
6. Reinstall cap on reservoir or heat exchanger.