Product Manual
Table Of Contents
- 25/30 EFI FourStroke
- Welcome
- Read This Manual Thoroughly
- Notice
- Warranty Message
- Copyright and Trademark Information
- Identification Records
- General Information
- Boater's Responsibilities
- Outboard Remote Control Models
- Exhaust Emissions
- Lanyard Stop Switch
- Protecting People in the Water
- Passenger Safety Message - Pontoon Boats and Deck Boats
- Wave and Wake Jumping
- High-Speed and High-Performance Boat Operation
- Impact with Underwater Hazards
- Safety Instructions for Hand-Tilled Outboards
- Safe Boating Recommendations
- Conditions Affecting Performance
- Recording Serial Number
- Model Year Production Code
- Component Identification
- Specifications
- Installation
- Transporting
- Fuel and Oil
- Features and Controls
- Operation
- Maintenance
- Cleaning Care
- EPA Emissions Regulations
- Inspection and Maintenance Schedule
- Maintenance Schedule Decal Icons
- Maintenance Schedule Decal
- Top Cowl Removal and Installation
- Cooling System
- Corrosion Control Anode
- Engine Oil
- Fuel System
- Gearcase Lubrication
- Lubrication Points
- Propeller Replacement
- Spark Plug Inspection and Replacement
- Storage
- Troubleshooting
- Owner Service Assistance
- Maintenance Log
- General Information
• High humidity
For you to have optimum engine performance under changing weather
conditions, it is essential that the engine be propped to allow the engine to
operate at or near the top end of the specified maximum RPM range with a
normal boat load during your normal boating weather conditions.
In most cases, recommended RPM can be achieved by changing to a lower
pitch propeller.
DETONATION
Detonation in a 4‑cycle engine resembles the pinging heard in an automobile
engine. It can be otherwise described as a tin‑like rattling or plinking sound.
Detonation is the explosion of the unburned fuel/air charge after the spark plug
has fired. Detonation creates severe shock waves in the engine. These shock
waves often find or create a weakness: the dome of a piston, cylinder head or
gasket, piston rings or piston ring lands, piston pin, and roller bearings.
A few of the most common causes of detonation in a marine 4‑cycle application
are as follows:
• Over‑advanced ignition timing
• Use of low octane gasoline
• Propeller pitch too high: engine RPM below recommended maximum
range
• Lean fuel mixture at, or near, wide‑open throttle
• Spark plugs: heat range too hot, incorrect reach, cross‑firing
• Deteriorated or inadequate engine cooling system
• Combustion chamber deposits: result in higher compression ratio
Detonation usually can be prevented if:
• The engine is correctly set up
• Regular maintenance is scheduled
PROPELLER SELECTION
IMPORTANT: The engines covered in this manual are equipped with an RPM
rev‑limiter that is set to an upper RPM limit. This limit, which is slightly above
the normal operating range of the engine, helps prevent damage from
excessive engine RPM. Once the RPM returns to the recommended operating
RPM range, normal engine operation resumes.
The boat manufacturer and the selling dealer are responsible for equipping the
power package with the correct propeller. Refer to Mercury Marine's web page
https://www.mercurymarine.com/en/us/propellers/selector/#/step‑one
.
Select a propeller that will allow the engine power package to operate at or
near the top end of the recommended WOT operating RPM range with a
normal load.
GENERAL INFORMATION
eng 15