How to get More Power

Getting more power from the Seagull outboard is difficult because of it’s limiting design. However, it’s not impossible. There is room for improvement in the following 9x areas

1. Porting ~ optimisation of port heights & time areas.
2. Exhaust ~ use tuned lengths & cones to maximise charging.
3. Squishbanding ~ modify the combustion chamber shape
4. BMEP ~ better the ‘brake mean effective pressure’ value
5. Fuels ~ use octane boosting & oxidising fuels & oxygen scavengers
6. Induction systems ~ improve flask resonance effects & carb size
7. Reed valves ~ replace the sideport, solve flutter & use synthetics
8. Crankcase compression ~ optimise this ratio
9. Ignition ~ improve the timing & coil magnetic saturation levels.

The research on finer internal working principles of the 2-stroke engine is very thorough & well recorded. By having a comprehensive understanding of the inner workings, you’ll be able to calculate modifications applicable to your engine to significantly improve power. Specifically recommended are the following 5x books:

  Two-stroke Tuner’s Handbook by Gordon Jennings.
This is very easy to read & written from a practical viewpoint

Two-stroke exhaust systems by Roy Bacon.
This gives a good simple explanation of the expansion chamber exhaust & practical solutions. Written with the fabricator in mind

Design and Simulation of Two-Stroke Engines by Gordon Blair.
Undoubtedly the most comprehensive book ever on two stroke theory with many formula derived from extensive laboratory testing. Written with the designer in mind

Two-Stroke Performance Tuning by A. Graham Bell.
A good balance of theory & practical viewpoints. Content is very able to be applied.

The High-Performance Two-Stroke Engine by John Dixon.
Easier to read than Gordon Blairs’ book.  Written by an experienced designer.