More grunt for Honda four strokes

Some boat owners have avoided fitting four-stroke engines to their craft because they feel the quiet-running engines don't have the explosive acceleration from rest that is the mark of many two strokes.

Honda has moved to eliminate this worry by incorporating its Boosted Low Speed (BLAST) system to every model of its four-stroke range from the compact BF40 up to the class-leading BF225.

The technology was first introduced on the BF75/90 models in 2006 and proved to be immediately popular. BLAST is activated by a sharp movement of the throttle to change the air-fuel ratio and ignition spark advance to provide more torque at low revs.

Honda Australia's assistant marine service manager Stephen Harvey says the patented technology gives the greatest torque at the precise moment it is required.

"The engine’s Electronic Command Unit (ECU) determines throttle opening during acceleration and advances the ignition timing to develop more horsepower at low revs," Harvey says, "A quick movement of the throttle control activates BLAST which aggressively advances the ignition curve."

Slow throttle advance allows the engine to operate as normal.

With BLAST, the air/fuel ratio goes to a richer setting during acceleration and the ECU determines the best spark advance.

"The boost in horsepower and torque at low revs contributes to very strong acceleration from 0-50 metres to get boats on the plane very quickly, something which was traditionally considered a weak point of four-stroke outboards,” Harvey says.

He says the BLAST technology has changed attitudes to four-stroke outboards the world over.