Keep Your Outboard Running And Add to Your Skillset

It happened all at once. Three friends were together and discovered all had outboards that wouldn't start. Seems this has become a common occurrence. While we often blame this on ethanol, it is not limited to ethanol-blended fuel.

I already addressed the issues of ethanol damage in one of my earliest post, where the water in the fuel corroded several jets and main nozzle to the point where they were encrusted and unable to pass fuel. Veteran cruiser and outboard expert, Will Heyer, helped us out and explained what he was doing and the steps needed to solve these issues and get the outboard running again. Go back to that post if you want to learn about that:

This time we have three outboards, each different but similar. The smallest is a two-stroke Yamaha rated at 2hp. It sat unused for a long time because it wouldn't start and a friend wants me to put it on my 9-foot Fatty Knees dinghy. The other two engines are both Mercurys, a 6hp and an electric start 9.9. Both are in pretty good condition and are work horses for seasonal boating on Chesapeake Bay. Which is why it is troublesome that none of these engines would start, or at least stay running.

So we enlisted Will Heyer again, and this time, he needed nothing special. As he explained his distaste for ethanol in gasoline, there are other culprits that cause difficulties. To jump to the end of this story, none of the outboards were affected by ethanol. The owner of the 6hp had even purchased ethanol-free aviation gas from a nearby airport to avoid that blended fuel.

The 9.9hp Mercury also had no corrosion issues, and in fact was ready to run except for dirt and/or crud that plugged some of the tiny holes in the various carburetor circuits, throwing the mixture off. 

The small Yamaha was fed 50:1, ethanol-free fuel from a can sold to power leaf blowers and other small two-stroke engines available at a local hardware store. But at the high cost of this specially packaged fuel, no cruiser would use this fuel option on a regular basis.

It was pretty clear after the first engine, that the issues surrounding the inability to start would be the same in all three outboards, namely that they needed to have their carburetors removed, all jets, nozzles, and passages cleaned to remove any tiny particles that might clog these small orifices at random. In each case, Will removed the fuel line, unplugged the breather line, took the carburetor off, unscrewed the four screws hold the bowl together and used carb cleaner, blowing air through a plastic tube to make sure the circuits and passages were no longer blocked. At no time was there was an obvious blockage to cause the problem, and whatever it was, it was too small to get our attention.

Just going through the process of cleaning the carburetor took care of the problem in all three engines and each started right up and ran like new. See this video of the Mercury 9.9 outboard as it went from cranky machinery to a fully operational outboard ready to serve simply by cleaning the carb. Again, nothing obvious was removed.

What causes small particles and junk to clog the jets and pores of the carburetor? It can happen in a couple of ways. There are no air cleaners on most outboards in the dinghy size range. Any dirt or dust in the ambient air can be drawn into the combustion process into the carburetor, even if it is unseen. There is simply no way to avoid dust and other particles in the air.

As for fuel filtration, on small outboards there is simply no space for any kind of filter, and other outboards just fit a small screen. The filters we find in larger outboards are still pretty basic, nothing close to the engineered filtration we employ on our diesel engines. A micron is 1/1000th of a millimeter. I don't know the size of the smallest holes in a carburetor body, but they are small. So what size filter do outboard manufacturers use if there is space to fit one? Local techs couldn't tell me but Internet research seems to indicate that fuel filters from major companies are in the neighborhood of 28 microns. (Remember, many brands of outboard engines are manufactured by one company, such as Tohatsu.) Whether this is fine enough filtration isn't clear. But particulates can enter the carburetion from different sources, so fuel isn't always the culprit. Will Heyer adds that the "crud" he finds in the bottom of a carburetor bowl is often a flaky mix, quite capable of breaking into tiny pieces capable of clogging those tiny holes that help transition from idle to acceleration.

One Mercury service tech told my friend that fuel injection has more or less eliminates many of the problems faced by today's outboards, but that is not available in small outboards, at least until Suzuki recently introduced EFI in their 9.9 and higher horsepower portable outboards. But portable is relative and these engines start at well over 100 lbs.

The alternatives today are few and far between. Locally on Chesapeake Bay, many cruisers use the small Torqeedo electric outboards, but when you begin looking at the 8hp equivalent motor, the price is considerably more expensive than a similar, four stroke gas outboard. If you cruise in waters outside the U.S., you can buy a two-stroke, which is even better, but your carbon footprint will never be as "green" as a four stroke engine.

A propane outboard is another option, and has many environmental benefits. But I've heard from several sources these engines lack quality control and company customer service is lacking. Perhaps that will improve, especially as Tohatsu enters the propane outboard market this year. That is something I really look forward to.

I did not include ALL possible propulsion options for your dinghy, such as this homemade long tail outboard created from a small two-stroke weed trimmer. Guess it works...

I did not include ALL possible propulsion options for your dinghy, such as this homemade long tail outboard created from a small two-stroke weed trimmer. Guess it works...

So where does that leave us? It seems clear that gasoline outboards are with us for awhile longer, so the best strategy is to become familiar with regular maintenance of your outboard engine. Will suggests having a couple of spare carburetor bowl gaskets on hand when you take things apart, but beyond carb cleaner, you do not need any tools you don't already have.

PassageMaker Magazine created a video at Trawler Fest in Stuart a few months back which provides a good idea of what to expect when you take apart, clean, and reassemble a typical four stroke carburetor:

While this fellow's technique is somewhat different than Will Heyer, you get the idea. He soaks the components (jets, nozzles, etc.) in carb cleaner or solvent for an hour or more, where Will takes a more proactive role, using his jet reamer kit to clean out all blockages, blow air through the passages and throttle body, then rinse the parts again with carb cleaner. He can turn it around rather quickly. 

The trick, according to Heyer, is to have a schematic of your carburetor on hand, so you know what all the pieces are and where they go. He mentioned an excellent source of parts and information is the online store, Below is from their website for the carburetor diagram and parts for a 2006 Tohatsu 6hp outboard. is a great resource for carburetor parts and complete spares. They seem to carry all major brands and are a good source to keep your parts locker fully stocked with parts and gaskets. is a great resource for carburetor parts and complete spares. They seem to carry all major brands and are a good source to keep your parts locker fully stocked with parts and gaskets.

The more I spend time with this subject, the more I am inclined to believe that an experienced cruiser should be able to maintain the carburetor of the dinghy's outboard. When you are far from outboard service facilities (and even if you aren't), it is not hard or difficult to clean a carburetor, and, in fact, it seems to take very little effort once you are familiar with the process. No special tools, just the correct diagram, and practice. There is not much adjustment either. Just be mindful of how many turns it took to remove a screw if it is meant to be adjustable. If it took 1.8 turns to unscrew it, do the same when you install it. I have included some typical adjustments from another owner's manual. But now having seen several carbs cleaned for routine maintenance (as opposed to dealing with corroded jets), it is straight forward and fine tuning is not really necessary unless you want to play with it. In fact, the mystery of gas engines, and outboards specifically, isn't all that mysterious once you get into it.

A page from an owner's manual on how to adjust a carburetor. While specific to one model, it is generally the same for all four stroke outboards.

A page from an owner's manual on how to adjust a carburetor. While specific to one model, it is generally the same for all four stroke outboards.

So there you have it. If you are a cruising family, maybe one of your mechanically inclined children could volunteer to become the "Outboard Whisperer" for your boat. If your daughter, for instance, enjoys dealing with small parts (it take only four screws to remove the carb bowl), and understands the process after a few run throughs, she'll have a wonderful new skillset that will not only extend her family's self sufficiency, but in no time your family will have lots more friends.

The trademark of a genuine mariner, a term that applies to both sailor and power cruiser, is self sufficiency. How better showcase that capability than by keeping your outboard engine purring like it should, always starting on the first pull. Knowing you can clean the carburetor in no time to get it going again without tiring, endless pulling of that starter cord is priceless.

Once again, I'd like to thank Will Heyer for demystifying another bugaboo of cruising, that cantankerous but necessary outboard.

Next week is our Independence Day holiday, so I may be offline with respect to posting new content. But I have lots more in the works.

Happy Fourth of July everyone!