Outboard Engine and Lower Unit Lubrication

The world of outboard marine power has been trending heavily the past decade toward more fuel-efficient and environmentally-friendly four-stroke outboards–away from the traditional two-strokes. This trend has been overall very positive in the sense that it gives the consumer a broader range of products to power their boats.

This change has slightly altered the way we maintain the product in some areas and yet there are a few basics that never change.

With the majority of engine manufacturer's emphasis being on reliability, the environment of the Texas coast where we operate presents very unique challenges and requires more frequent and focused attention in certain aspects of maintenance.

Engine lubricants for all outboards, four-stroke and two-stroke, are currently of the best quality that has ever been available and provide excellent lubrication and protection of internal components–bearings, pistons, piston rings, etc.

Engine crankcase oil is serviced at 100-hour intervals in four-strokes or, in the case of two-strokes, is added each time main reservoir level is consumed at an average rate of one gallon of oil to 30- to 40 gallons of fuel, depending how the engine is operated. Engine oil engineering compensates for all rpm ranges.

The lower unit gear case oil for use in all outboards is also currently of excellent quality and is subject to much more rigorous and varying demands of temperature and terrain, (usually fully submerged but sometimes jacked-up to the extreme of six inches out of the water on tunnel hulls) in coastal boating applications.

The lower unit oil should be checked at minimum every quarter on a year-round boating schedule by removing the lower drain screw to inspect a sample of the lubricant for water contamination (water turns lube milky), fine metal filings, and also odor (burnt lube has a distinctive smell compared to new).

The propeller should be removed to check for fishing line wrapped on the prop shaft at least once a month during peak usage and a new stainless cotter key or tabbed locking washer installed each time.

No matter how good oils are made and improved for lower unit gear cases, the lack or absence of this oil combined with the intrusion or complete replacement of lube with salt water due to fishing line destroying prop shaft seals and allowing water to enter the gear case, will shorten the life expectancy and/or destroy this piece of well-engineered equipment.

Water can actually be considered a lubricant of sorts, but sorely lacking in its ability to deliver protection to the bearings and gears in a lower unit gear case. Gear lube is very inexpensive by comparison.

Enjoy a safe and fun winter boating and fishing season!

Chris Mapp
Coastal Bend Marine | Port O'Connor, TX coastalbendmarine.com | 361-983-4841