Hi,
I have a 2005 Mercury 50HP 4 stroke EFI outboard and recently it started to lack power and seems to be overheating. I have done a lot of reading on this forum and other forums about similar problems, but have not been able to solve my problem. I believe if I solve my lack of power issue, I will also solve the overheating at the same time. The motor lacks power as soon as I turn it on and not just when it has overheated, so I believe the lack of power issue is also causing the overheating, unlike some peoples issues where they have overheat then a lack of power because of the gaurdian system. If I run long enough, 10 to 15 minutes at high to full throttle I will get the alarm. I had the boat on the river the other day and I had to limp it back up river, stopping every so often and run in neutral to let it cool down, so I could get more power and make it back to the boat launch. When I got back, my motor was quite hot, but only on the left side (looking from behind the boat to the front) in the upper-mid section of the motor.
Here is what I have done...
1. I pulled the lower unit and inspected the water impeller. The impeller looked in excellent shape and there is a good stream of water from the tell tale.
2. I took out the thermostat, it looked a little gummed up with scum and dirt, but when I put it in a pot of water and heated it up, it seemed to open right around 120F and when I took it out of the hot water, it slowly closed. It appeared to operate just fine.
3. I removed all spark plugs and tested the compression on all cylinders. The compression was 170 to 175 psi on all cylinders. The only thing I noticed was on the top cylinder, where the spark plug threads into the cylinder, it was spotless. All other cylinders looked to have a blackish/brown color in this location. I am not sure if that is an issue or not, but something I noticed. The spark plugs themselves on the other hand all appeared the same.
Finally, this is what I am going to do...
1. I have ordered a new impeller and will be replacing the old one.
2. I have ordered a new thermostat and will be replacing the old one.
3. I will be replacing all spark plugs.
I do not believe the thermostat or impeller are going to fix my problem, but feel it is a cheap thing to change. The spark plugs I am skeptical as well, but don't know enough to know whether they may be an issue or not.
Does anybody else have any suggestions to try, remember I have loss of power right away and I believe this is what is resulting in the overheating. The motor also seems to cool down and not overheat when just at an idle.
Thanks
I have a 2005 Mercury 50HP 4 stroke EFI outboard and recently it started to lack power and seems to be overheating. I have done a lot of reading on this forum and other forums about similar problems, but have not been able to solve my problem. I believe if I solve my lack of power issue, I will also solve the overheating at the same time. The motor lacks power as soon as I turn it on and not just when it has overheated, so I believe the lack of power issue is also causing the overheating, unlike some peoples issues where they have overheat then a lack of power because of the gaurdian system. If I run long enough, 10 to 15 minutes at high to full throttle I will get the alarm. I had the boat on the river the other day and I had to limp it back up river, stopping every so often and run in neutral to let it cool down, so I could get more power and make it back to the boat launch. When I got back, my motor was quite hot, but only on the left side (looking from behind the boat to the front) in the upper-mid section of the motor.
Here is what I have done...
1. I pulled the lower unit and inspected the water impeller. The impeller looked in excellent shape and there is a good stream of water from the tell tale.
2. I took out the thermostat, it looked a little gummed up with scum and dirt, but when I put it in a pot of water and heated it up, it seemed to open right around 120F and when I took it out of the hot water, it slowly closed. It appeared to operate just fine.
3. I removed all spark plugs and tested the compression on all cylinders. The compression was 170 to 175 psi on all cylinders. The only thing I noticed was on the top cylinder, where the spark plug threads into the cylinder, it was spotless. All other cylinders looked to have a blackish/brown color in this location. I am not sure if that is an issue or not, but something I noticed. The spark plugs themselves on the other hand all appeared the same.
Finally, this is what I am going to do...
1. I have ordered a new impeller and will be replacing the old one.
2. I have ordered a new thermostat and will be replacing the old one.
3. I will be replacing all spark plugs.
I do not believe the thermostat or impeller are going to fix my problem, but feel it is a cheap thing to change. The spark plugs I am skeptical as well, but don't know enough to know whether they may be an issue or not.
Does anybody else have any suggestions to try, remember I have loss of power right away and I believe this is what is resulting in the overheating. The motor also seems to cool down and not overheat when just at an idle.
Thanks
