Any number of things can cause your engine’s temperature to spike. Some are a serious threat, others are not. The worst possibilities include loss of compression because of damaged rings or valves, lubrication issues, main-bearing problems, mis- firing, and more. Any of these normally require a good mechanic and can be pricey to fix. But often, a spike in temperature signals a temporary
malaise that will have few long-term consequences if quickly remedied.
1Check for cooling water coming out of your exhaust or the “pee hole” in the outboard. If the volume of water has diminished or if there’s white steam (which may look like extra
exhaust), not enough water is going through the engine to cool it. You’ll need to work
through the next few items to find the problem. But if the cooling water is spewing out normally, check your voltage. A voltage change at the gauge, as when
you turn on the instrument-panel lights, could, in some installations,
cause a slight increase in the temperature reading that has nothing to
do with the engine.
2Turn off the engine immediately, if safe to do so. Do not restart until it cools down to within normal operating temperatures.
Usually the engine temperature will continue to increase after shutdown because it’s no longer getting any cooling water. Restarting at
the higher temperature may ruin the engine. Always wait until the
engine has cooled before you work on it.
WHAT IF YOUR TEMPERATURE GAUGE SPIKES?
When your engine’s got a fever, quick action will often save the patient.
Here’s what to do when things start to heat up
92 | BoatU.S. Magazine
3Check for obstructions. When debris blocks the cooling water intake or clogs
the strainer and restricts water flow, failure to
remedy the problem immediately can result
in the destruction of the impeller and other
more serious problems. Debris in a raw-water
strainer for an inboard is easily fixed by turning off the engine, closing the thru-hull valve,
and cleaning the strainer. An inboard engine
may suck a large piece of debris, such as a
plastic bag, onto your strainer outside the
hull, particularly if you’re moving slowly. On
outboards, plastic or even seaweed over the
cooling intake vents will prevent water from
reaching the engine. Often on outboards
and inboards, just shifting into reverse for a
moment will clear the debris over the intake.
4On an inboard, check the V-belt. A sudden high temperature rise can be
caused by the breakage of the V-belt on an
inboard with an enclosed cooling system.
This will cause the freshwater recirculation
pump on the forward end of the engine to
stop turning. This should be easy to fix with
a temporary “fits-all” belt or a spare belt if
you have one.
5Look for connection problems in the raw-water system. In a freshwater-cooled inboard, a sudden high temperature
spike could indicate a busted cooling-water
hose or loose hose clamp, which
has allowed a hose to back
off its nipple. This will
also cause flooding.
may be prone to
upon the situation, you may
be able to temporarily repair a
busted hose with
Rescue Tape, or
BOATER ENGINE TROUBLESHOOTING BY TOM NEALE
Keeping a close
eye on your gauges
may save you some
headaches later on.