OUTBOARD SERVICE BULLETIN
POWERHEAD
No. 2276 Rev.1
April, 1994
SUBJECT: Cooling System Modifications
MODELS: 1986 thru 1994 70 HP / 1987 thru 1994 65 HP / 1989 thru 1994 60 HP
PROBLEM: An engine can be damaged by overheating when air becomes trapped in the upper half of the cooling system. This can happen when the engine is idling with a blocked or restricted thermostat bypass hole, or the engine operates in aerated water, such as a pontoon boat wake.
SOLUTION: Locating the water pump indicator outlet tee to the top of the cylinder block ensures air can be vented from the cooling system and an adequate water level in the cooling system can be maintained at idle:
STEP 1: Remove the indicator hose from the tee and discard hose. Remove tee from exhaust manifold cover. Seal the original hole with plug PN 321164. Apply OMC Gel-Seal II to threads of the plug.
STEP 2a: Measure 2-inches (51-mm) forward from the rear corner of the exhaust manifold cover [A]. Measure in from the exhaust cover gasket 1-3/8-inch (34-mm) [B]. Mark the intersection with a center punch. [See drawing]
- DwgStep2OMC_Cooling.jpg (13.95 KiB) Viewed 8476 times
NOTE: Grease the tips of both the drill and tap to prevent aluminum chips from entering the cooling system.
STEP 2b: To prevent damage to the water jacket, mark an 11/32-inch (letter-R) drill bit so that the drill will not penetrate more than 1/2-inch (12,7-mm). Drill a hole through the casting and tap threads to 1/8-inch-NPT. Apply OMC Gel-Seal II to the threads of the original tee and install in hole so the water pump indicator nipple is facing the rear.
STEP 3: Cut a new piece of hose 19-inch (48 cm) long from a roll of 1/16-inch (4,76-mm) ID hose PN 913435. Install new hose.