I love the smell of two-stroke exhaust in the morning. And if your outboard was new during the Reagan administration, you know what I mean. Those old outboards were built tough, and plenty of them are still running strong today.
Like anything mechanical, however, an old outboard needs some love. Rubber ages, parts wear, and corrosion runs its course. Pretty soon that faithful old Johnson is letting you down. Read on for some tips to help your old outboard avoid or overcome the ravages of time.
Buy the Book
A service manual will provide valuable guidance. Usually available from authorized marine dealers but also from on-line service literature dealers, or even on eBay, the service manual will explain how to take things apart and put them back together, list essential specifications and maintenance information, and include details like the location of all lubrication points.
Age, heat, and ethanol can deteriorate rubber and plastic components in the fuel system. This can cause dangerous fuel leaks or allow air to be drawn into the system and make the motor hard to start or keep running. Fuel lines will become hard and brittle, and actually deteriorate from the inside-out.
Aged fuel pump diaphragms and check valves can also make an outboard hard to start. It’s not too big a job to simply replace all of the fuel lines on an outboard with hose made of modern materials designed to withstand ethanol. Get marine-specific, ethanol-rated fuel line from your dealer. There are also kits available to rebuild pulse-type fuel pumps that include new, ethanol-tolerant diaphragms and check valves. Same goes for a kit to rebuild the carburetors. If the carb kit doesn’t include a new float, be sure to also replace that component. A rehabilitated fuel system will be safe and function at peak efficiency.
It doesn’t touch fuel, but the rubber impeller of the water pump will get dry and stiff with age, especially if the motor is not used frequently. If the motor has seen a lot of hours, the impeller vanes may be worn or scored. Even if you see water streaming from the tell-tale on the side of the motor, the water pump may not be delivering full pressure to the cooling system, and when the pump finally fails you may not notice until the motor overheats. Replacing the impeller is really cheap insurance. Also inspect the pump housing, which on many motors can be replaced if it’s been scored by abrasive sand. Finally, inspect the water intake port(s) on the lower unit to make sure they are not blocked with debris–a stiff wire can be used to poke them clear.
Obviously if the propeller is in rough shape, a replacement or a repair is going to improve overall performance. Even if the prop looks okay, its blades may be slightly bent from impacting a soft bottom or the blade cupping may be worn; it’s thus no longer in balance or correctly pitched. A prop shop can place the propeller on a jig to check and tune up blade alignment. Of course, propeller design has come a long way in the past 30 years. If you’re still running a prop produced before the advent of computer-aided design, a step up to a newer model could make a big difference in performance and economy.
While you’ve got the prop off the motor, check for fishing line wrapped around the shaft near the propshaft seal; it can destroy that seal and let water enter the gearcase.
The really weak link on an old prop is the rubber hub cushion. Like the fuel system and the water pump impeller, the rubber hub material gets hard and dry as it ages and is constantly exposed to hot and acidic exhaust. The bond between hub splines and the barrel of the prop can fail when the hub material dries out, leaving the propshaft disconnected from the prop. Beware an old prop from dealer stock—a marine tech I know thought he’d struck pay dirt when he found a 30-year-old NOS stainless-steel Mariner prop for his 25 HP motor, gathering dust in a dealer stockroom. Even though it was “NOS” (new on shelf) the hub was dry and spun out the second time he used the prop.
Spark Plugs and Wires
Most outboard owners know to throw a new set of plugs in a two-stroke outboard every season. But like everything else rubbery on an outboard, heat and ozone will cause the spark plug wires or cables to age with time and they should also be replaced. Old wires will feel stiff or brittle, and will develop small cracks in the insulation that can allow current to arc out of the wires. One way to check for arcing is to start the motor in the dark with the cowl off, and look for white or bright blue flashing where the current is escaping the cables and grounding somewhere on the motor. New plug cables will ensure all that current reaches the plugs.
Rebuild the Recoil
If your motor has a manual rope-start (the so-called Armstrong System), it will likely benefit from a rebuild. Mounted on top of the powerhead, the recoil is exposed to a lot of engine heat, and also gets baked in the hot sun, especially under a black cowl. The lubricating grease gets old and waxy, and the entire mechanism can become polluted with dirt and minerals from the water. The rope itself will age and get stiff and become prone to breaking, usually at its end where it’s crimped around the spool or pulley.
The service manual will be especially helpful for this task, as the recoil often has a number of small parts and a spring or two to deal with. Get it apart and use solvent to clean off any old grease. Replace any parts that appear worn, like rope guides or pawls that grip the flywheel. Re-lube and then reassemble with a new rope or cable.
Finally, give that old outboard a hug—everyone needs some love now and again.