1. Dalan Zartman CRS, FF II, FI II, EMTP Rescue Methods 2014 ©

2. Outboard Motors The outboard motor selection must begin with the required hp to effectively operate in the prescribed environment with the designated payload. This is typically driven by the boat manufacturer based on load capacity, application, and boat design.

3. 2 Stroke Enhanced performance power to weight ratio Simplistic Acceleration and Torque Emission equivalent to 4 Stroke technology Fuel economy comparable to 4 stroke technology

4. 4 Stroke More Complex Cleaner emissions in most cases Quieter Greater fuel economy in most cases Decreased power to weight ratio

5. Jet drives vs Prop drives Jet Drives Fast Shallow Resilient Inefficient Require propulsion to steer Prop Drives Slower Easily damaged in shallow water Efficient Can steer without propulsion due to rudder control

6. Additional Considerations Tiller control Trim Fuel Maintenance Reliability Shaft Length

7. Conclusion Typically speaking, 2 stroke outboard motors with prop drives are optimal for swift water applications due to their weight to power ratio resulting in greater acceleration and reactive maneuverability in all water conditions.

8. Props Durability Affordability Performance

9. 3 Blades Faster top end speed Less Torque and acceleration Material and Design impact performance

10. 4 Blades Greater torque Slower tope end speed Greater acceleration and maneuverability in all water conditions Material and design impact performance

11. Prop features Diameter Pitch Rake Cup

12. Diameter Distance from tip to tip The greater the blade, the greater the water displacement and thrust The greater the blade, the greater the demand for torque and hp

13. Pitch Pitch results in the theoretical distance traveled per revolution Low pitch equals fast acceleration but lower top end speed High pitch equals slow acceleration but greater top end speed

14. Rake Rake impacts the bow of the craft and its ability to plane out and reduce drag Increased rake brings the bow up but may result in instability Decreased rake brings the bow down but may result in increased drag

15. Cup Cup maximizes the efficiency of the blades ability to “grab” the water. Reduces ventilation and slipping Increases Rake Increases Pitch

16. Trouble Shooting Ventilation (often confused with cavitation) is the result of air pockets which make a prop lose its thrust. This manifests as free climbing RPM’s without gaining speed. Typically caused by lack of power, high transom mountings, extreme trim, or sharp turns. Corrective actions: Anti ventilation plate orientation Prop Configuration – Increase Cup Increase hp

17. Trouble Shooting Cavitation occurs when a combination of decreased pressure and increased temperature cause gas bubbles to form which in theory “boil” and vaporize or implode causing pitting and scorching to the prop. Typically caused by flaws or imperfections and damage to the lower unit or anti cavitation plane. Can also be caused by continuous or excessive ventilation. Corrective Action: Eliminate ventilation problem Insure lower unit is undamaged

18. Trouble Shooting Inability to plane out will typically occur when the boat is underpowered, overloaded, or trimmed out inappropriately. Corrective Actions: Insure weight and load to power ratio is correct Adjust trim Prop Configuration – Increase Rake

19. 2 Tinga Specifications Recommendations Minimum 40 hp 2 stroke outboard Maximum 60 hp 2 stroke outboard 4 blade prop with maximum diameter and minimum pitch and rake, moderate cup Transom Spacer Hands on training