Keeping in Tune

The key to maintaining your boat

The boating season is well under way with your engines, drives and boat all in running order. Now you need to ask yourself: how do you maintain the reliability, safety, economy, and performance of your equipment?

Years of R&D testing, poker runs, and weekend excursions have proven that fine tuning can improve your boat’s performance (sometimes 1-3mph) and increase your engine’s life without making internal motor modifications or larger horsepower engine swaps.

Regular oil and filter change every 50 hours are standard maintenance. Each engine manufacturer develops their own grades of oil which are always on hand at your Iocal dealer.

Keeping abrasive materials away from moving internal parts, pistons, cranks, the cam and bearings, will add to the life of your engine.

Properly tuning the engine to the manufacturer’s specifications is a critical job, one that should be done by a trained technician. Tuning up includes changing spark plugs, caps, and rotors. As most boaters know, we quite often neglect these things until they finally fail. Spark plug wires should be checked at least every two years, if not annually. This is a critical safety point. Old spark plug wires with cracked insulation can ground out, causing sparks inside the bilge -which can be very disastrous, with the possibility of fire or explosion.

Properly adjusting the carburetor is another important tuning step. Inspect it for leaks. Make sure that linkages and chokes are functioning properly. If problems arise in any of these areas, the carburetor should be rebuilt by a qualified technician.

Let us assume that the oil has just been changed and is clean, and the engine is in tune, operating in the manufacturer’s top rpm range. For engine longevity, if specs call for4600 – 5000 rpm, then try to stay as close as possible to 5000 rpm – but not exceed it!

You can accomplish this by working with different props. Propping is a science with a multitude of styles, sizes, and manufacturers. It is best to consult your manufacturer or dealer. Not only does your dealer have a supply of props on hand, they also will know what will work best with your boat’s size and power. The right prop will enable your boat to perform at its maximum potential.

An engine will also achieve its maximum horsepower with a cooler air charge going down the carburetor. Ideally, the bilge temperature should be as close as possible to the outside air temperature.

To test your engine compartment temperature, tape a thermometer to the forward engine bulkhead. Take your boat out to open water and run it at wide open throttle for at least five to eight minutes, allowing everything to reach maximum temperature in the engine compartment. At the end of your run, slow the boat as quickly and safely as possible. Shut the engine off and lift the hatch to read the thermometer. Record the reading – it is probably a lot higher than the outside air temperature.

Another quick test for cooling and air flow – which should be done only under controlled conditions – is to run the boat at wide open throttle with the engine hatch raised about an inch, or off. If you notice any gain in mph and./or rpm, you have restricted air flow and possible high bilge temperature.

Two things can influence running temperature: venting in the engine compartment (bilge vents) and the size and condition of the flame arrester (breather) on top of the carburetor.

Most boat manufacturers will install enough vents to exhaust any bilge at low to mid-range speeds, but not enough to keep temperatures down at higher speeds. In most cases, adding one or two more vents per side will bring the temperatures down.

A flame arrester has several functions. It filters the air flow into the carburetor and will also retain any flame in the carburetor that is caused by a backfire. Hence the name “flame arrester” or “spark arrester. “Keeping the flame arrester clean is very important for engine economy, safety, and performance. By allowing the mesh screen to get clogged with particles, you restrict air flow to the carburetor. This makes the engine run rich, as if the choke were stuck on, causing the engine to slow down. Usually, the flame arrester supplied with a stock engine is at its maximum flow. In most cases, going to the next larger size will enhance the breathing capabilities, especially when you add extra bilge vents.

Remember, lower air temperatures and more air flow equals more horsepower. All of these changes can help any engine use… whether cottage boating or high-speed poker runs.