When a New Impeller Isn't Enough.

A common scenario in marine repair: You replace the raw water impeller, but the engine still runs hot. This usually points to a failure in the "closed" side of your cooling system—specifically the circulation pump or the thermostat.

While the raw water pump brings sea water in, the circulation pump moves the engine coolant through the block. If this pump fails or your thermostat sticks closed, the coolant boils inside the engine, leading to warped cylinder heads and blown gaskets. We provide the advanced diagnostics needed to catch this before it destroys your engine.

Our Diagnostic Process

We don't guess; we test. Using thermal imaging and pressure tools, we isolate the issue.

• Infrared Thermal Analysis: We use laser thermometers to scan the engine block, manifolds, and risers while running. This identifies "hot spots" that indicate a blockage or a stuck thermostat.
• Circulation Pump "Weep Hole" Check: We inspect the underside of the pump for coolant trails. A leaking weep hole is the first sign of impending bearing failure.
• Thermostat "Pot Test": We remove the thermostat and test it in heating water to verify the exact temperature at which it opens—or if it opens at all.
• Belt Tension & Pulley Alignment: A loose belt can cause the pump to slip and under-perform at high RPMs.

Signs of a Circulation System Failure

• Overheating at Idle: Often points to a circulation pump issue.
• Temperature Spikes: The gauge fluctuates wildly instead of staying steady.
• Coolant in the Bilge: Sweet-smelling green or orange fluid under the engine.
• Engine Hot, Risers Cool: A classic sign of a stuck thermostat preventing flow.

Why Choose Breeze Marine?

• Systematic Approach: We understand the physics of both Half-Systems and Full-Closed Cooling systems on Mercruiser and Volvo Penta engines.
• Preventative Focus: We recommend changing thermostats every 3-5 years as cheap insurance against engine failure.
• Mobile Diagnostics: We bring the testing equipment to your boat, saving you a tow to the yard.

Is Your Temperature Gauge Climbing?

Don't let a $50 thermostat ruin a $10,000 engine. Call us for a cooling system audit today.