Specifications for an Engine Tune-Up of a Mercruiser Marine Engine 470

by David Curtis
A Mercruiser 470 tune-up helps keep the engine running efficiently.

A Mercruiser 470 tune-up helps keep the engine running efficiently.

Maintaining a Mercruiser 470 stern drive system regularly keeps the engine running efficiently and increases dependability. There are two basic types of tune-ups for these systems. The basic tune-up consists of replacing the ignition system parts only. A full tune-up encompasses the ignition, engine and stern drive systems.

Mercruiser 470 Specifications

The Mercruiser 470 engine is a four-cylinder, 170 horse power engine. The 470 has a 3.8 liter Ford-based engine, coupled to a Mercury Alpha one outdrive. The engine is unique because of its closed-cooling system. This system utilizes antifreeze, along with pumped lake water, running through a heat exchanger for engine cooling. It also has an engine stator and regulator for battery charging. These parts were often faulty and expensive to replace. This has resulted in aftermarket kits that convert the charging system to a regular marine alternator.

Basic Ignition Tune-Up

The basic tune-up consists of inspection and replacement of worn ignition parts. The parts included in the ignition system are the distributor cap, rotor, points, condenser, spark plug wires and spark plugs. These parts are sometimes available as a kit from most marine shops and may be found at a local automotive parts supplier. It is necessary to check the timing on Mercruiser 470 engines each season to ensure the ignition is advancing properly. A visual battery inspection and power test should be performed, with full replacement if any weakness is revealed.

Engine Tune-Up

This tune-up process begins with a visual inspection of the engine components. Inspection of the exhaust gaskets and bellows for leakage, wiring for any frayed or disconnected ends, and all belts and hoses for cracking and softness. The flame arrestor, located over the carburetor, is normally cleaned with mineral spirits or brake cleaner. Fuel filter, engine oil and filter replacement each season is an inexpensive way to keep the engine operating efficiently and reliably. The Mercruiser 470 closed cooling system antifreeze level is checked through the small reservoir cap located at the top front area of the engine.

Outdrive Tune-Up

Yearly inspection of the propeller for damage and repair is recommended. Prop removal and the application of bearing grease to the propshaft keeps hub corrosion to a minimum. Inspection and replacement of the outdrive gear fluid each season is a good preventative maintenance task that will dramatically increase gear and bearing life. A milky color in the lubricant is an indication of water contamination and should be investigated and addressed immediately. The Mercathode system is sacrificial zinc metal bonded to the electrical system that protects the drive unit from pitting and corrosion. Checking and replacing these metal parts regularly are vital in keeping the drive unit from being damaged while in the water.

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