Boating Tips


Posted 4/28/2010

A car's transmission and gears help its engine run within its most efficient rpm range at any speed, therefore putting less pressure on the engine and requiring a lower viscosity oil.  Because outboard engines do not have transmissions, it is not unusual for an outboard to turn over 5500 rpm at top speed. The extreme pressure endured by outboard engines causes more friction and therefore outboards require specialized, heavy viscosity oil for maximum protection.  Choosing an oil not recommended by the outboard manufacturer can make a huge difference in the proper lubrication of the outboard and can ultimately result in damage to the engine.

Here's a situation that happens more often than we would like. A customer invests thousands of dollars in a new outboard, then puts generic oil of questionable origin from some discount store in the engine. Before long, that customer is usually crying the blues when the powerhead fails because of inadequate lubrication.

Does it really matter what oil you use in your outboard? Well… yes, it really does. You wouldn't put cooking oil from the kitchen in your car, so why on earth would one even consider using anything but high-quality, outboard-specific lubricants in an outboard motor?

At these high rpms, the crankshaft, connecting rods, pistons, camshafts, and dozens of other moving parts can turn the oil to a frothy mix. That's why marine oils contain special anti-foaming agents to help the oil stay in its original liquid state for maximum lubricating protection, no matter how fast the engine is running.

Oilology 101
Outboard oils are certified by the National Marine Manufacturers Association (NMMA®) by undergoing a stringent regimen of scientific evaluations to ensure the oils are up to the task of lubricating the engine, even in the harshest of conditions.

For two-stroke outboards, the NMMA® created a standard called TCW-3® (two cycle water cooled, third revision of certification requirements). Here is a brief excerpt from the NMMA's TCW-3® Two Stroke Oil Certification Program paper:

"The tests include varied bench tests for fluidity, lubricity, viscosity, etc., plus the oil must meet minimum ring sticking and carbon build up on pistons in engine tests."

With the proliferation of four-stroke outboards, the NMMA® kept pace with the industry, issuing the FW-C® (four cycle water cooled) standard for oils that passed grueling aeration, foaming, viscosity, filter-clogging tests, as well as exhibiting excellent anti-corrosion properties.

Automotive vs. Outboard Oils
Automobile and four-stroke outboard engines have vastly different operating parameters; therefore, they each require oils to meet their needs.
Cars have transmissions with multiple gears to help the engine run in its most efficient rpm range – it's not unusual to be cruising down the highway at 70 mph at around 2000 rpm. In addition, increasing demand for maximum fuel economy has led to a trend in very thin (low viscosity) automotive oils to reduce friction on the engine's internal components.

Outboard engines don't have transmissions, so when you put the shifter in gear and push down on the throttle, the engine is under a tremendous load – like trying to drive a car up Pike's Peak in the highest gear. And because outboards lack transmissions, it's not unusual for the engine to be turning over 5500 rpm at top speed – a huge difference when compared to a car.

Outboard engines are boat powerplants. Boats are operated in water, subjecting the outboards to moisture (directly or indirectly) that can get into the oil. Corrosion inhibitors and other additives in marine oils aid in preventing rust and make sure the oil maintains its ability to adequately lubricate the powerhead.

Two-Stroke Oils
TCW-3® oils take care of the unique needs of the two-stroke outboard by (obviously) offering great lubrication, reduce piston rings from sticking and carbon build-up in the combustion chamber, and are mixed to burn cleaner to prevent fouling spark plugs, while lowering exhaust emissions in the process.

C'mon, Oil is Oil – Does it 
Really Matter Which Marine Oil I Use?
The engineers who design outboards also play a major role in specifying the oil requirements for the engines, so it only makes sense to use the oil from your engine's manufacturer to ensure your outboard is getting the best lubrication possible.

NMMA® FW-C® and TCW-3® certifications are simply the minimum standards for marine engine oils. Most marine engine manufacturers' engine oils far exceed these minimum standards, because their oils are formulated for their engines and the manufacturers want the outboards they make to provide boaters with years of fun on the water, without the hassles of oil-related engine issues.

Frankly, it's tempting to save a few bucks on off-brand generic oils, but why put your outboard at risk? The difference in price between the engine manufacturer's oil and the stuff you buy at the convenience store won't matter that much when you are faced with the cost of fixing your outboard due to ineffective lubrication.