Troubleshooting Outboard Acceleration
There are several reasons your boat might not be getting the speed that it should. It may feel like the boat has lost acceleration or simply won’t run at full speed anymore.
If you feel your outboard isn't accelerating like it should, there are a few things you can check for to determine why your outboard feels like it’s losing speed or acceleration.
Check the Engine
Inspect the fuel lines for obstructions that could impede fuel flow between the tank and the motor. Check for kinks, cracks, or anything else that might be blocking a fuel line. A dirty fuel filter can also clog the fuel system, so make sure the filter is clean.
The air intake can suffer from the same basic issues as the fuel system. Obstructions can reduce airflow, which means less air to mix with fuel to create combustion. Check the intake to make sure there are no obstructions, and make sure the air filter is clean if your outboard has one.
Inspect the propulsion system for tangled fishing line and aquatic plants, which can cut into RPMs and keep the propeller blades from getting a firm bite in the water.
You may also want to consider the prop itself. A prop with high pitch gets you more acceleration, while one with a lower pitch gets you more raw speed. Outboards typically have a WOT (Wide Open Throttle) rating, which gives you an RPM target for when the throttle is wide open. If the RPMS are higher than the WOT rating when you have the throttle wide open, the prop is geared more toward acceleration, and you may be giving up speed.
On the other hand, if you open up the throttle and you can’t get the RPMs you want, the pitch might be too much for your outboard, and that may be keeping the prop from turning efficiently and getting the speed you want. But even if you have the right prop, damage can cause it to not run efficiently, leaving some speed on the table.
One more thing to think about: a clean boat is a fast boat. Algae growing on the hull keeps water from flowing smoothly around it, so cleaning a dirty hull can make a noticeable difference in performance.