Marine Cooling System Calculator
Size raw water cooling components for marine engine installations
Cooling System Specifications
Required Water Flow
--
Heat Rejection
--
Minimum Intake Hose Size
--
Sea Strainer Size
--
Through-Hull Size
--
Total System Flow (All Engines)
--
Pump Pressure Required
--
Temperature Rise
--
Standard Flow Requirements
| Engine HP | GPM Required | Min Hose ID |
|---|---|---|
| 50-100 | 8-15 | 3/4" |
| 100-200 | 15-25 | 1" |
| 200-350 | 25-40 | 1-1/4" |
| 350-500 | 40-60 | 1-1/2" |
| 500-750 | 60-90 | 2" |
Marine Cooling System Guidelines
Sizing Principles
Rule of thumb: 1 GPM per 10 HP for diesel engines, 1 GPM per 8 HP for gasoline engines.
Through-hull should be same size or larger than engine intake. Never reduce below manufacturer spec.
Sea strainer should have minimum 2x the open area of intake hose cross-section.
Installation Best Practices
Install scoop-type through-hull facing forward for positive pressure underway.
Locate strainer above waterline if possible for easy cleaning. Use seacock on all through-hulls.
Use proper marine hose rated for raw water service. Double-clamp all connections below waterline.