Why is my boat accellerating slowly?

Stalling, slow accelleration, no power or bogging out when trying to plane off are common complaints in the boating world.  Although not always, but very often, it ends up being a fuel related problem.  Possible problems could be a tank full of bad gas, cracked or leaking fuel lines, restricted fuel primer bulb, plugged fuel pick ups, clogged filters, bad fuel pumps, dirty carburetors/fuel injectors, or all of the above.

When checking for fuel problems, the first step would be to take a fuel sample.  Make sure there is no water in the fuel and the fuel smells fresh.  Old gas smells like varnish.

The next step to do is eliminate the boat fuel system from the motor, for example, by running on a six gallon portable tank and hose.  If it is still running poorly, you know there is a problem with the motor.  A quick easy way to check the fuel pump is to give the bulb a good squeezing while running to see if the motor picks up RPMs (on a carbureted motor), or you can use a fuel vacuum and a fuel pressure gague to check fuel pump operation.  Note: the readings and connection points will vary depending on the engine manufacturer and model, check the service manual for instructions and specifications. 

Finally, the last step is to see if the carburetors of fuel injectors are supplying enough fuel to the cylinders.  To do this, I run the motor at the speed where the problem occurs and carefully squirt some fuel into each intake one at a time and see if the engine RPMs increase.  If they do, that would indicate clogged carburetors or injectors.

Keep in mind that if all these components are not properly checked and taken care of you will have continuous problems.