Honda Marine - Technical Talk

Selecting the correct shaft length is fundamental to the correct matching of boat and engine. Honda engines come in a range of different shaft lengths to assist the boater in selecting the correct engine. For example the Honda BF2 is the only two-horsepower outboard on the market with a long shaft option available.

Should the wrong shaft length be chosen the performance of the boat will be affected. For example, if a long shaft is fitted to a low transom the propeller will be too deep in the water. The engine will probably

operate but its efficiency would suffer and excessive fuel would be used trying to drag the lower unit through the water.

If a short shaft engine were fitted to a transom requiring a long shaft the propeller would be too high, and cut through air and water, possibly causing damage to the engine. Cavitation may occur when making turns.

Measure your boat transom using the guide diagram.

To determine outboard shaft length requirement, subtract your boat transom height and the motor transom height. The difference should be approximately 0-2 inches which is the installation height range.

Always check your boat to match the correct length. Yacht auxiliary motors are often long shaft. Most inflatables, sailing dinghies, fishing and rowing boats tend to be short shaft. Many yachts require an Extra Long Shaft.

As a general rule the outboard should be installed so the anti-cavitation is parallel to the bottom of the boat. For further installation click here.