http://www.indmar.com/About/ContactIndmar/Manual_2003_Presentweb.pdf

http://www.marineenginedigest.com/diy/8simplerules.htm

The "health" of an inboard's lubricant is critical, because marine power plants run hotter than their automotive counterparts. They also work much harder. They're either idling dockside or under constant load. Offshore, there are no hills to coast down. Even when trolling or transiting a no-wake zone, a marine engine has its nose to the veritable grindstone.

Ambient air temperature in marine engine compartments is higher than the temperature of the air surrounding an automotive engine. In fact, marine engines are like mini-oil refineries, cooking off a lubricant's lighter molecules and leaving behind the heavier molecules. As the engine logs hours, its oil transforms into a sticky varnish--which is why oil changes are so vital.

The two images on the lower left show an oil cap removed on an engine which has benefited from regular oil changes and an oil cap removed on an engine which has not had its oil changed at reasonable intervals, compounded by being stored with dirty oil in the engine. Note the thick sludge.

Procedure:

Run engine to warm engine oil. Drain engine oil, change engine oil filter and refill with recommended SAE engine oil. Run engine to check for leaks. Recheck oil level.