I have a 2005 Mercury 60hp 4 stroke Bigfoot. The past several times we have taken the boat out it has a loss of power issue. When I first launch, the motor cranks fine and I let it sit and idle while we are getting life jackets on all the kids and getting everyone seated. The motor then runs fine going to our beach spot (about a mile and a half). After sitting for a few hours, when we either go to leave, or if I take the kids to pull them on a tube, the boat will start fine and idle good, then when I go to take off, when it gets to full throttle, after a minute of running at full throttle, it starts losing power and RPM’s. The motor also starts running rough. If I bring the throttle all the way back down and ease back into it, it seems to correct itself and then runs fine. It seems to follow this same scenario every time.
A couple weeks ago, we went out and ran for about 30 minutes up river with some friends and it ran perfect, after sitting for about an hour, I took the kids to pull them on the tube and it started the losing power at full throttle, backed it down to idle, took back off and ran fine for about 20 minutes of pulling the tube. Then went back to the sand bar and it sat for a few more hours. We them packed up and headed back to the launch, started fine and was fine at about half throttle. When I went to open it up to full throttle, lost power and running rough again, backed it down to idle for a minute and then went back to full throttle and ran perfect for the 30 minutes back to the launch.
Today we had it out and again, started up perfect and idled great. Ran perfect for about two miles to a restaurant. Docked at the restaurant long enough for the family to eat and then headed for the beach. Motor ran perfect for another two miles to the beach and We parked there for about 4.5-5 hours. We loaded up and headed back to the launch and it got up to full throttle for about 45 seconds to a minute and started losing power. I brought it back to half throttle to try that and it was still losing power, so I brought it back down to idle and again, it ran perfect the 3.5-4 miles back to the launch.
I have replaced the fuel line from the tank to the motor, the filter and the primer bulb. Four new NGK plugs and replaced the fuel filter that is inside the motor cowling.
Anyone have any idea what this could be? If it matters at all, I typically have the motor trimmed up when we are sitting as we are typically beaches where we go. But I do trim back down so the lower part of the motor is in the water before starting the motor up.
Thanks in advance.
A couple weeks ago, we went out and ran for about 30 minutes up river with some friends and it ran perfect, after sitting for about an hour, I took the kids to pull them on the tube and it started the losing power at full throttle, backed it down to idle, took back off and ran fine for about 20 minutes of pulling the tube. Then went back to the sand bar and it sat for a few more hours. We them packed up and headed back to the launch, started fine and was fine at about half throttle. When I went to open it up to full throttle, lost power and running rough again, backed it down to idle for a minute and then went back to full throttle and ran perfect for the 30 minutes back to the launch.
Today we had it out and again, started up perfect and idled great. Ran perfect for about two miles to a restaurant. Docked at the restaurant long enough for the family to eat and then headed for the beach. Motor ran perfect for another two miles to the beach and We parked there for about 4.5-5 hours. We loaded up and headed back to the launch and it got up to full throttle for about 45 seconds to a minute and started losing power. I brought it back to half throttle to try that and it was still losing power, so I brought it back down to idle and again, it ran perfect the 3.5-4 miles back to the launch.
I have replaced the fuel line from the tank to the motor, the filter and the primer bulb. Four new NGK plugs and replaced the fuel filter that is inside the motor cowling.
Anyone have any idea what this could be? If it matters at all, I typically have the motor trimmed up when we are sitting as we are typically beaches where we go. But I do trim back down so the lower part of the motor is in the water before starting the motor up.
Thanks in advance.
