Engine Maintenance Chapter 7 Outboard Engines and Drives, and Stern Drives

2 Objectives for the Student 1.Have a good understanding of the component parts of the outboard marine engine and how these parts work together to propel the boat through the water 2.Have knowledge of the fuel, lubrication, cooling, exhaust, ignition and electrical systems needed for the outboard engine to function properly 3.Have an understanding of the stern drive that is used in inboard/outboard operation

3 The Marine Drive System Outboard Systems Power Head Intermediate Housing Lower Unit

4 Outboard Engine Crankcase Similar to conventional crankcase, but designed to work vertically Similar to conventional crankcase, but designed to work vertically Different bearing design Different bearing design Dry sump lubrication Dry sump lubrication

5 Outboard Engine Crankshaft Bearings are designed for vertical operation Bearings are designed for vertical operation Relies on mist lubrication Relies on mist lubrication

6 Outboard Engine Pistons Long skirt to valve intake and exhaust ports Long skirt to valve intake and exhaust ports No oil control grooves No oil control grooves Domed head to scavenge cylinder gases Domed head to scavenge cylinder gases

7 Outboard Carburetion Multiple carburetors are common Multiple carburetors are common Individual carburetors are simpler than inboard engine designs Individual carburetors are simpler than inboard engine designs

8 Outboard Lubrication Oil mist lubrication Oil mist lubrication Usually requires oil and fuel to be premixed Usually requires oil and fuel to be premixed Can be injected from oil reservoir Can be injected from oil reservoir No sump required No sump required No oil cooling benefit No oil cooling benefit

9 Outboard Cooling and Exhaust Cooling derived from impeller pump in lower unit Cooling derived from impeller pump in lower unit Most water cools the exhaust Most water cools the exhaust Exhaust is vented through the propeller hub Exhaust is vented through the propeller hub

10 Outboard Ignition Magneto Magneto Coil energy is provided by magnet in engine flywheel Coil energy is provided by magnet in engine flywheel Distributor / breaker point Distributor / breaker point Same as inboard engines Same as inboard engines Solid state Solid state

11 Outboard Drive Systems

12 I/O Drive Systems Inboard engine Inboard engine Outboard drive system Outboard drive system Generally pierces the transom, not the hull Generally pierces the transom, not the hull

13 Tilt and Trim Systems Mechanical on small drives Mechanical on small drives Hydroelectric on larger systems Hydroelectric on larger systems

14 Routine Maintenance Service twice per season Service twice per season Check lower unit lubricant and replace if necessary Check lower unit lubricant and replace if necessary Replace zincs as needed (when >50% consumed) Replace zincs as needed (when >50% consumed) Check boots and seals for cracks Check boots and seals for cracks

15 Winter Storage Prevent freezing Prevent freezing Check and replace lubricant as needed Check and replace lubricant as needed Replace zincs as needed (when >50% consumed) Replace zincs as needed (when >50% consumed) Warm the engine, then change the oil Warm the engine, then change the oil Run potable antifreeze through the raw water system Run potable antifreeze through the raw water system Check boots and seals for cracks Check boots and seals for cracks Paint housing if needed Paint housing if needed

16 Spring Service Should not be necessary! Should not be necessary!

17 Remember… You should be able to identify problems and explain them to a mechanic