TROUBLESHOOTING
SERVICE MANUAL NUMBER 24
Engine Overheats (Cooling System)
Cause
Special Information
IMPORTANT: The first step is to verify if the engine is actually overheating or the
temperature gauge or sender is faulty.
IMPORTANT: Best way to test gauge or sender is to replace them.
Loose or faulty drive belt
Seawater shutoff valve partially or fully
closed (if equipped)
Clogged or improperly installed sea
strainer
Loose hose connections between seawa- Pump will suck air. Pump may fail to prime
ter pickup and seawater pump inlet (mod- or will force air bubbles into cooling sys-
els with belt driven seawater pump only)
Seawater inlet hose kinked or collapsed
Seawater pickup clogged
tem.
Obstruction will be in front of seawater
pickup, causing air bubbles to be forced
into cooling system
Obstruction on boat bottom causing water
turbulence
Defective thermostat
Exhaust elbow water outlet holes plugged
Insufficient seawater pump operation
Worn pump impeller
Obstruction in cooling system such as
casting flash, sand, rust, salt, etc.
Refer to water flow diagram for engine
type being serviced
Engine circulating pump defective
Also refer to “Engine Overheats (Mechanical)”
IMPORTANT: In addition to previous checks, make the following checks if engine
is equipped with closed cooling.
Low coolant level
Antifreeze should be mixed 50/50 or maxi-
Antifreeze not mixed properly
mum 60/40 (60% antifreeze, 40% water)
Heat exchanger cores plugged
Water hoses reversed at the water dis-
Refer to water flow diagram in SECTION 6
tribution block
Index
Page 1C-28
90-861327--1 OCTOBER 1999
| Categories | Mercury MerCruiser Manuals |
|---|---|
| Tags | Mercury MerCruiser 305 CID, Mercury MerCruiser 350 CID |
| Model Year | 1998, 1999, 2000, 2001 |
| Download File |
|
| Document File Type | |
| Copyright | Attribution Non-commercial |
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Marine readers have rated Mercury MerCruiser Engines Service Manual Number 24 GM V-8 305 CID 350 CID 4.0 out of 4.0 based on 1 product reviews. Great performance engine.
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