An engine that pulls fine for 15 minutes then loses RPM is almost always fuel starvation or overheating — and it's predictable enough to diagnose in one trip.
What to Check
1
Fuel filter clogging
Tank crud lifts at high fuel demand and clogs the primary filter. Replace and check the bowl.
2
Anti-siphon valve sticking
Old anti-siphon valves stick partly closed under load — remove and bench test.
3
Fuel pickup tube
A blocked or cracked pickup tube can't supply WOT fuel demand.
4
Cooling system creeping hot
Some ECUs reduce RPM to protect the engine before the temp gauge moves. Check raw-water flow at WOT.
When to Call Us
We bring electronic flow meters and pressure gauges to your slip — diagnose under-load issues without dragging the boat to a shop.