Service manual

MAINTENANCE

SERVICE MANUAL NUMBER 26

90-861329--1 MARCH 1999 Page 1B-9

Crankcase Oil

To help obtain optimum engine performance and to provide maximum protection, we

strongly recommend the use of Quicksilver 4-Cycle 25W-40 Marine Engine Oil. This oil is

a special blend of 25-weight and 40-weight oils for marine engines. If not available, a good

grade, straight weight, detergent automotive oil of correct viscosity, with an API service

rating of SH,CF/CF-2 may be used.

In those areas where Quicksilver 4-Cycle 25W-40 Marine Engine Oil or a recommended

straight weight oil is not available, a multi-viscosity 20W-40 or, as a second but less

preferable choice, 20W-50, with API service ratings of SH,CF/CF-2 may be used.

IMPORTANT: The use of non-detergent oils, multi-viscosity oils (other than

Quicksilver 25W-40 or a good quality 20W-40 or 20W-50), synthetic oils, low quality

oils or oils that contain solid additives are specifically not recommended.

The chart below is a guide to crankcase oil selection. The oil filter should always be changed

with the engine oil.

SAE 20W

SAE 30W

SAE 40W

32° F

° C

° F

° C

AIR TEMPERATURE

75796

Overfilled Crankcase Oil

Overfilled crankcases (oil level being too high ) can cause a fluctuation or drop in oil pressure

and rocker arm “clatter” on MerCruiser engines. The over-full condition results in the engine

crankshaft splashing and agitating the oil, causing it to foam (become aerated). The aerated

oil causes the hydraulic valve lifters to “bleed down.” This, in turn, results in rocker arm

“clatter” and loss of engine performance, due to the valves not opening properly.

Care must be taken when checking engine oil level. Oil level must be maintained between

the ADD mark and the FULL mark on the dipstick. To ensure that you are not getting a “false

reading,” make sure the following steps are done before checking the oil level.

• Boat “at rest” in the water, or

• If boat is on a trailer, raise or lower bow until the boat is setting at the approximate angle

that it would be if setting “at rest” in the water.

• Allow sufficient time for oil to drain into the crankcase if engine has just been run or oil

has just been added.

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