The sound of a smooth running outboard motor on a fishing or pleasure boat brings joy to boat owners, but it works the opposite way too. It’s distressing to hear an outboard motor squealing, skipping, making metallic sounds or sputtering. An even worse scenario is an outboard motor that won’t start at all or suddenly quits and won’t restart.

Outboard motors are instruments of fun when they take you to your favorite fishing spot or enable you to cruise the lake, river or ocean. They are instruments of torture when they leave you stranded, capable of ruining a carefully planned boating outing that you looked forward to for days. It’s easy to take an outboard motor for granted, but like all running equipment, regular maintenance can determine the difference between fun and torture. In the following sections, the ins-and-outs of outboard motors are discussed – types of motors, typical problems, maintenance and repairs, and the repair-or-replace decision.

Sounds of Silence…or Not

Outboard motors can make strange noises when there’s a problem developing. Of course, there is also the sounds of silence when the engine won’t crank or quits while running. It’s a tragic scene when a boater having fun is now trying to repair an engine while floating in the middle of the lake. It can be downright embarrassing when unable to leave the dock because the boat owner never found time to do simple maintenance tasks. Asking for a tow from a nearby boater is also embarrassing because it means you have now interrupted someone else’s fun too.

Misery really doesn’t love company. Forget that old expression!

Many of the common problems with outboard motors can be avoided, while some are just the result of equipment failure. Life happens. Following are some the ways boaters get stranded.

  • Engine cranks but won’t turn over – Not to evade an answer, but there could be many reasons an engine just won’t start, ranging from a serious component failure to a loose hose. A simple reason could be the common problem of a faulty emergency cut-off switch. Disconnect the emergency kill switch, and see if the engine starts. Always start simple and work your way up to, “I need a marine technician.”

  • Engine overheats – Boat motors are subject to blockage because raw water is full of debris, marine critters, plants (think weeds or seaweed), pollution particles, etc. The water the boat is on is used to cool the engine, meaning what is good for the engine can also become a problem. Check all spots of raw water intake for blockage, and remove whatever might be causing the problem. Other potential causes include a split water hose or a loose water hose clamp.

  • Engine runs a while, quits and won’t restart – This could easily indicate the engine is not drawing fuel. The fuel tank vent could be blocked if the tank is installed. If it’s a portable fuel tank, check to make sure the vent is open.

  • Boat runs rough – A damaged propeller blade can create a serious vibration that gets worse at higher speeds. It’s amazing that even a small dent can cause such a big vibration. The same is true when something like fishing line wraps around the prop’s hub. You can try putting on your spare prop (you did bring one, right?) or clearing the prop hub of whatever has wrapped around it. Sometimes though, it is a more serious issue like failing rubber brushing inside the propeller hub.

  • Telltale is not streaming water – The telltale is a small vent in the engine that emits a thin visible stream of water. The stream lets you know the cooling water is flowing as it should. When the telltale hole is plugged or the water stream is weak, check the outlet tubing for blockage. You can run some fishing line into the hole and twirl it. If this doesn’t work after a few tries, the impeller may be broken. Time to visit the marine mechanic.

  • Engine stalls in neutral at idle speed – In this case, the engine starts, runs well in neutral but shuts down when in idle speed. It could be the automatic idle speed valve is sticking. A professional marine technician will need to replace the valve.

  • Engine sputters and loses power – When the engine seems to be losing power but doesn’t actually quit, there could be several possible reasons. One is there are fouled plugs. Another is an in-line fuel filter clogged just enough with debris to cause a problem. Hopefully you have a spare fuel filter on hand.

  • Engine refuses to start – The silence is deafening. The first culprit that comes to mind is a dead battery. But it could be a break in the ignition circuit, a loose ignition switch or (darn it) something more complicated like a technology problem such as a failed chip in a board. If you’re lucky, someone accidentally pulled the lanyard to the kill switch. Most boaters aren’t that lucky though, so don’t get your hopes up too high.

  • Engine won’t shift into gear – There is a good chance the linkage in a mechanical cable shifter is broken or stuck. Another possibility is the shifter cable has corroded and detached from the shift lever on the gear box. Of course, it could be a transmission failure.

These are not all of the potential problems that can make you panic or leave you stranded. A hose on the engine cooling and exhaust system inside the cowling could break, or there could be a major breakdown in which there is a complete electronic failure. Hopefully an expensive failure is not due to lack of maintenance.

Tools of the Trade

Faithfully maintaining your outboard is crucial to avoiding problems. There are many tasks the boat owner can personally do throughout the year. Some tasks are best left to a professional outboard motor mechanic. In this section, we consider some items you should always carry on the boat, the maintenance items you can do regularly, and the maintenance and repairs a qualified marine technician should manage.

Emergency Repairs

Anyone who owns an outboard motor needs to be prepared to make small emergency repairs. There are two points to keep in mind:

  1. Keep the engine maintenance manual onboard and not in your desk drawer at home. You would be surprised how many manuals are left behind!

  2. Keep basic tools and some critical boat supplies or spare parts onboard. They include:

  3. Spark plugs

  4. Battery connector
  5. Spare fuel-water separator filter for when the engine sounds an alarm and shuts down before water in the fuel gets into the system
  6. Special tools recommended by the manufacturer, like a specific wrench
  7. General tools like a stiff wire brush to clean corrosion, socket set with extension (1/4-inch or 3/8-inch), vice grip pliers, screwdriver set that includes a Phillips, etc.
  8. General supplies like fuses, duct tape, electrical tape, anti-corrosion spray, zip ties (of course!), spare hose clamps, etc.
  9. Spare propeller with extra cotter pins (if you are taking a long trip, then carry a couple of spare propellers)

How many boats have limped home with temporary repairs made with zip ties and duct tape? Want a rough ride? Hit your propeller on a rock, bend a blade and hang on.

Ongoing maintenance by the boat owner

There are plenty of preventive maintenance items you should faithfully and routinely manage. Following are some of them:

  • Check for engine corrosion in general
  • Check for oil buildup close to the prop or oil buildup that gets worse, indicating the lower unit seal might be leaking
  • Two-stroke engines require oil injection so keep the oil injection reservoir full
  • Four-stroke motors require regular oil and oil filter changes
  • Regularly check for debris in the water intake system
  • Flush the engine after every use in salt or fresh water to keep debris out, attaching a garden hose to a special port (if the engine has one) that doesn’t require running the engine but will flush water into cooling-water passages; if the boat is kept on a trailer, use “ear muffs” which is a flushing attachment enabling going around the water pickups so you can use a garden hose while running the engine in idle or neutral speed for a few minutes
  • Keep the motor’s moving parts lubricated, i.e. carburetor linkages, throttle cable, shift cable, etc.
  • Maintain all fluid and gear oil levels
  • Regularly check the shifter cable end fittings and hardware
  • Inspect the fuel line for wear and tear or cracks
  • Ensure the fuel primer bulb is always in good condition
  • Check the fuel tank for corrosion or rust
  • Regularly check the motor’s aluminum components for corrosion from salt water, i.e. mounting bracket, steering components, cables, etc.
  • Check the rubberized gasket around the cowl base (engine cover that prevents immersion in water) for leaks
  • Check the cowl’s baffled intakes that allow air in while shedding water to keep them clear of debris
  • If a mechanical cable throttle and shift system, keep the cable lubricated and inspect for wear
  • Visually inspect fuel-water filters for water collection (fuels with ethanol can turn into a problem)
  • Check for rust or corrosion in the filter canister which can create a major fire hazard
  • Change fuel-water filters periodically (50-100 hours of running time), using a 10-micron cannister-style fuel filter to capture the ethanol gunk
  • Use a fuel additive if using fuel with ethanol (see the following explanation)

One of the things to be aware of is that modern outboard motors are not designed to burn gas that has more than 10-percent ethanol. Ideally, you will use gas that has no ethanol, but that’s not always possible. Even .5-percent water in fuel can lead to phase separation. This is when gas and ethanol separate, the ethanol combines with water, and a sticky gunk falls to the bottom of the fuel tank. If the ethanol gunk gets into the fuel system, the engine components are very likely to be damaged. The fuel additive can help prevent this disaster.

Maintenance and repairs by a marine mechanic

An outboard mechanic near you should always service the motor on an annual basis or based on the hours of operation, as recommended by the manufacturer. There are maintenance and repairs that only a trained mechanic should do because they require specialized training and tools Marine motors today are controlled by digital technology, so the average boat owner cannot repair the engine in many situations. Engine diagnostic software that can assess the computerized components is needed to evaluate the motor’s operating condition or to troubleshoot a problem. Following are some points to keep in mind:

  • Four-stroke motors are more difficult to repair and need regular maintenance checks by a professional marine technician
  • Four-stroke engines require periodic valve adjustments
  • Valve replacements should only be done by qualified marine technicians
  • Let a professional service the engine per the manufacturer’s recommendations for service intervals, i.e. lube the gear case or change filters
  • Only a qualified marine mechanic should replace the impeller
  • Faithfully follow the maintenance recommendations per the manufacturer (minimum annually or based on hours of operation) which includes the traditional items like new oil filter, oil change, new spark plugs, and new gas filter plus diagnostics and general inspection
  • Have a marine mechanic inspect the wiring to look for worn, broken, damage wires and wire ends
  • Only a marine technician should handle transmission repairs

Repair the Old Outboard or Buy a New Outboard

As is true for all equipment, there is an age-old discussion on whether to repair or replace the outboard engine. Replacement includes buying a rebuilt or a brand new motor. One of the first considerations is the age of the outboard motor, but there are others. Maybe you are just ready for a newer motor that is fuel efficient, environmentally-friendly and high tech.

Let’s face it – there is a bit of boat and motor envy taking place on the water. Go ahead and admit it!

Some considerations include:

  • Age of the motor being replaced – If your boat has been used in salt water for more than 10 years, you probably need to buy a new engine. Saltwater is so corrosive, and you are tempting fate by continuing to use the motor. If the boat was primarily used in fresh water, you can consider having the motor rebuilt.

  • Parts availability – If your outboard is older than 1985, expect to start having trouble finding repair parts. The other issue is that technology in outboard motors has radically changed in the last two decades. Pre-1985 outboards should be scrapped when they fail. Post-1985 outboard motors might be eligible for a rebuild – emphasis on maybe.

  • Cost – Sometimes the cost of rebuilding an outboard motor is more than the cost of buying a rebuilt or new motor. It depends on the type of motor you have or want.

  • Power and weight requirements – You may decide you want more power. Monohull boats under 20-feet in length that were built after 1972 are required to have a boat builder’s capacity plate that lists the maximum horsepower. Boats over 20-feet may or may not have a capacity plate. Outboard motors today are available in a wide range of horsepower – most in the 2.3 to 350 horsepower range. There are some that have even more horsepower, but they are unusual.

    The size of the outboard motor should fit the size of the boat and it’s intended use. If you find your motor no longer fits your needs then you may need to buy a new outboard. For example, you used to do a lot of quiet fishing but now need to pull your kids on skis. Consider the outboard motor’s stroke, weight and power requirements.

  • Usage – The type of waters your boat must master can lead to buying a new outboard motor with newer features. Do you need a power thrust feature so you can brave strong currents or an electric start because pulling the engine rope has become too difficult and precarious in bad weather?

  • Peace of mind – Some people just like knowing their motor is under warranty or is newer and less likely to break down.

  • Newest and greatest – There are also people who just like owning the newest smartphone, the newest vehicle and the newest outboard motor. There’s nothing wrong with that attitude, if the budget can handle it.

One option is to buy a used rebuilt boat motor which may come with a warranty if purchased from a boat dealer. It’s important to consult with a professional boat mechanic too. If you are interested in repowering your boat with a bigger and better outboard motor, find an outboard motor mechanic near you to determine what it will require. For example, do you need to replace the fuel system, or should you install a new steering system? These are the kinds of items that need the marine technician’s expertise.

Masters of the Water Universe

Should you buy a two-stroke or four-stroke outboard motor? Consider the features of each – weight, power, maintenance needs, local emissions requirements, type of boat the motor will power, acceleration needs (think getting to that big bass first), and noise factor. Yes, it’s a lot to take into consideration, but remember you may use the outboard motor for over a decade before it’s time to decide again. Mariner Exchange has made it easy for boat owners from coast-to-coast to find expert maintenance and repair technicians who are always willing to share their knowledge.

We would like to add the new outboard motors are things of beauty – sleek and high tech. Once merely workhorses, they have become masters of the water universe.