I am having an issue with my 60hp yamaha F4.
When running at full speed (over 5000RPM) the engine bogs down and drops RPM’s. This does not happen at a regular interval sometimes it happens every few minutes and other times it can go for 10-15 minutes without a problem.
To bring the RPM’s back up somebody needs to pump the ball at the fuel tank. If somebody sits back there and pumps the ball every few minutes there will not be a problem. I do have the air vents open on the fuel tank.
This was happening last year and I noticed one of my tanks would leak around the hose connection. If gas can leak out air could get in so I got a new fuel tank and hose and the problem was fixed. I did not have any issues at all from May – October. Then the boat sat until January. This is when the problem re appeared and it has been giving me grief ever since.
I have tried both fuel tanks (one only a year old) and both fuel lines and it does not make a difference. I am hoping somebody can point me in the right direction as to what to look for and how to test it.
I’m wondering if it could be my fuel pump and if so how to test it. Are there any fuel filters in the engine that should also be checked? The engine starts great every time and runs really strong as long as somebody is pumping the ball. The engine has about 380 hours on it. Thanks for any help you can offer.