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2004 25HP Yamaha four stroke outboard model number - F25ELHC
Motor is mounted on a 16' 9" 2004 Smoker Craft - Motor has appr. 450 hours
Has been a great running motor for many years with nothing but preventative maintenance things completed each year as required. Water pump was last replaced in the fall of 2015. This past week the boat was warmed up normally and nothing appeared wrong. Boat did have a normal water stream while sitting at the dock. After leaving the marina heading across the lake at full throttle (approximately 23 mph) it started feeling like the boat was loosing power. I was thinking it was just the wind and then I started noticing it was really starting to lose power for sure. Looked back and saw some steam and then it shut down. Removed the cover and it was definitely hot. After getting back to the marina and allowing the engine to cool four about 4 hours, it was restarted and was determined to have a water pump failure. But did appear to be running okay. So now what and what else was hurt by the heat buildup? After a visual inspection of the motor I did not see any paint peeling or any other heat marks. Decided to replace the Water Pump Assembly and Thermostat Assembly. After these replacement the motor ran well in the bucket of water at the shop and had a good stream of water. However, at the marina the motor ran fine at low idle but when I tired to apply more power it did not like it. The motor would basically vibrate hard and just not ran very well - could not accelerate at all. Back to the shop. Next we replaced the plugs because it was acting like it was fouling. Back down to the marina and we still had the same problem. Now what? Basically the shop I am using has a bunch of great people but they are not a Yamaha shop. So it was decided to leave it for the weekend and make some calls on Monday. Well, I was supposed to be fishing in a tournament this weekend and could not so a bunch of my fishing friends got together and started helping with their ideas and thoughts. We checked the fuel filter and just looked things over when someone asked what about the temperature sensor (thermistor)? Could it be bad (shorted or open)? I then measured the unit with a ohmmeter and I found that it was shorted out - zero ohms. I looked up some information on it and if I am understanding it correctly 0.0 ohms would tell the motor (computer or CDI unit) that it was still very hot therefore would still be locked in "Limp Home Mode". I also noticed that when trying to run it in the marina if the rpm's was at 1200, 1500, or even 1850 it would run great and was very smooth running. However, once I tried to go above 2000 rpm's the motor would just start cutting out again. Could this be the reason why it is not running correctly? I no this is very long but I wanted to make sure you had the complete history. So what do you think? If this is it, have I missed anything else? And what does CDI stand for in the service manual? My assumption is it's the Computer. Assuming this does fix the problem will the motor be okay after all of this? Thank you for your time and comments.
Motor is mounted on a 16' 9" 2004 Smoker Craft - Motor has appr. 450 hours
Has been a great running motor for many years with nothing but preventative maintenance things completed each year as required. Water pump was last replaced in the fall of 2015. This past week the boat was warmed up normally and nothing appeared wrong. Boat did have a normal water stream while sitting at the dock. After leaving the marina heading across the lake at full throttle (approximately 23 mph) it started feeling like the boat was loosing power. I was thinking it was just the wind and then I started noticing it was really starting to lose power for sure. Looked back and saw some steam and then it shut down. Removed the cover and it was definitely hot. After getting back to the marina and allowing the engine to cool four about 4 hours, it was restarted and was determined to have a water pump failure. But did appear to be running okay. So now what and what else was hurt by the heat buildup? After a visual inspection of the motor I did not see any paint peeling or any other heat marks. Decided to replace the Water Pump Assembly and Thermostat Assembly. After these replacement the motor ran well in the bucket of water at the shop and had a good stream of water. However, at the marina the motor ran fine at low idle but when I tired to apply more power it did not like it. The motor would basically vibrate hard and just not ran very well - could not accelerate at all. Back to the shop. Next we replaced the plugs because it was acting like it was fouling. Back down to the marina and we still had the same problem. Now what? Basically the shop I am using has a bunch of great people but they are not a Yamaha shop. So it was decided to leave it for the weekend and make some calls on Monday. Well, I was supposed to be fishing in a tournament this weekend and could not so a bunch of my fishing friends got together and started helping with their ideas and thoughts. We checked the fuel filter and just looked things over when someone asked what about the temperature sensor (thermistor)? Could it be bad (shorted or open)? I then measured the unit with a ohmmeter and I found that it was shorted out - zero ohms. I looked up some information on it and if I am understanding it correctly 0.0 ohms would tell the motor (computer or CDI unit) that it was still very hot therefore would still be locked in "Limp Home Mode". I also noticed that when trying to run it in the marina if the rpm's was at 1200, 1500, or even 1850 it would run great and was very smooth running. However, once I tried to go above 2000 rpm's the motor would just start cutting out again. Could this be the reason why it is not running correctly? I no this is very long but I wanted to make sure you had the complete history. So what do you think? If this is it, have I missed anything else? And what does CDI stand for in the service manual? My assumption is it's the Computer. Assuming this does fix the problem will the motor be okay after all of this? Thank you for your time and comments.
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