Mercury 250 EFI Outboard Not Running Right.....Tips Anyone?
08-29-2016, 07:27 AM
#1
Mercury 250 EFI Outboard Not Running Right.....Tips Anyone?
Hello All,
After a beautiful weekend on the water I had a terrible drive home on Sunday afternoon due to my 1997 Mercury 250 EFI acting up. Here is the full back story and was hoping someone can help out, maybe know the problem or suggest what to check. I have a few ideas but would love other peoples ideas. I am going to give a full backstory so that everyone has the whole history:
So I have twin motors on my boat and one motor started acting up when I used my boat in Florida in April. The motor was starving for fuel and I would need to have my friends pump the bulb when the tank was under 1/4 full. I got annoyed with that, switched lines and the other motor was doing the same thing. After, swapped pickups for that motor and it seemed to fix the issue.
Next issue I fixed was in July where I replaced the bushing/motor mounts that are located under the power head. Everything seemed to go smoothly. Unplug everything from the motor that needed, pull the powerhead off, replace, put power head on and plug everything in.
In the end of July that same motor started acting up again. The motor would not get over 5000 RPM when it use to hit 5500 or so. In July it was barely getting to 5000, mostly at 4600 to 4800 RPM and I honestly think it would go to 5000 because the other motor is pushing the boat to allow it to get to 5000. I ran it like that for 2 weekend and didn't have time to really look into it (thought maybe a bad gas, just cranky motor for that day and wanted to test it more).
Now Last week, I installed 2 in-line Garmin fuel sensors (one for each motor) after the Fuel Water Separator on these engines. With those sensors comes a fuel filter, 30 Micron in-line before the sensor. Put the boat in and pumped both bulbs. That same motor started giving me issues like it had air in the line. Pumped the bulb it got better but still wouldnt go full RPM, in fact, it would just hit 4000 RPM MAX. The night got late and I needed to go so I docked the boat for the week.
This Weekend, first time on it since it did that, I figured I would make sure that bulb is fully primed before I left. When I went for my ride it wouldn't go over 4000RPM and it wouldn't stay at 4000 either. Again, good motor would hit 5500, other motor would do 4000 for a min boost to 4200 sometimes, then back to 3200 for a long time then to 4000 then maybe 4400 then back to 4000 then 3100 for a bit. It was just all over the place, not in a fast way but it would hold for a min to 10 min like that to sometimes 30 seconds. It did this for 65 miles. Go to my destination (I still go the boat to do 35MPH) and didn't have enough tools to do a full diagnosis but all weekend long it did that. I even filled the tank with more fuel, 89 with Valvtec.
On Sunday on the way home, Started out the same issues with that same bad motor for 30 min then the other GOOD motor acted up. It was starving for fuel going from 4000 to 3000 to 2500 to 3000 to 2000 to 3000 RPM'sl. I had to have my gf sit on the back pumping that bulb for 20 min, even stopped, turned off the motor, pump the bulb to full hard 3 times before the good engine acted normal for the rest of the 1.5 hour drive home.
When all this was acting up the bad motor was fluctuating from 2000 to 3200 and I think it was because the other motor wasn't pushing like it use to. Once I got my "good" motor to stay alive / get back to normal, I set that to 4000 and the other one (original bad motor) to 3000 and cruised home. Right outside my home I played with it to see if the "Problems" went awa. Open her up full throttle and good motor went to 5200 bad motor did not even come close, 4000 Max.
So here are some of my thoughts and I would love suggestions or ideas what to fix / check please.
1) Bad fuel pump. Possible for both engines but deff bad on that one. Are these a mechanical or electric fuel pump? Is there a low pressure and high pressure pump?
- Reason I think its a weak pump is that originally it wouldn't hit 5000 now it barely hits 4000 with a added fuel filter. Maybe the restriction of that fuel filter is making it harder to pump the fuel to the motor?
2) Clogged fuel filters. I will change my Water Separator, but any other filters to check? Is there a filter before the injectors? I know Yamaha has a VST (or something like that) filter before the injectors that are known to clog and cause issues like this. Does mercury?
3) Bad / Clogged injectors. I am thinking of sending them out at the end of the season any ways but could it be just those?
Again, if anyone had this issue, seen this issue, fixed this issue, or just might have some other ideas please let me know. I greatly appreciate that!
After a beautiful weekend on the water I had a terrible drive home on Sunday afternoon due to my 1997 Mercury 250 EFI acting up. Here is the full back story and was hoping someone can help out, maybe know the problem or suggest what to check. I have a few ideas but would love other peoples ideas. I am going to give a full backstory so that everyone has the whole history:
So I have twin motors on my boat and one motor started acting up when I used my boat in Florida in April. The motor was starving for fuel and I would need to have my friends pump the bulb when the tank was under 1/4 full. I got annoyed with that, switched lines and the other motor was doing the same thing. After, swapped pickups for that motor and it seemed to fix the issue.
Next issue I fixed was in July where I replaced the bushing/motor mounts that are located under the power head. Everything seemed to go smoothly. Unplug everything from the motor that needed, pull the powerhead off, replace, put power head on and plug everything in.
In the end of July that same motor started acting up again. The motor would not get over 5000 RPM when it use to hit 5500 or so. In July it was barely getting to 5000, mostly at 4600 to 4800 RPM and I honestly think it would go to 5000 because the other motor is pushing the boat to allow it to get to 5000. I ran it like that for 2 weekend and didn't have time to really look into it (thought maybe a bad gas, just cranky motor for that day and wanted to test it more).
Now Last week, I installed 2 in-line Garmin fuel sensors (one for each motor) after the Fuel Water Separator on these engines. With those sensors comes a fuel filter, 30 Micron in-line before the sensor. Put the boat in and pumped both bulbs. That same motor started giving me issues like it had air in the line. Pumped the bulb it got better but still wouldnt go full RPM, in fact, it would just hit 4000 RPM MAX. The night got late and I needed to go so I docked the boat for the week.
This Weekend, first time on it since it did that, I figured I would make sure that bulb is fully primed before I left. When I went for my ride it wouldn't go over 4000RPM and it wouldn't stay at 4000 either. Again, good motor would hit 5500, other motor would do 4000 for a min boost to 4200 sometimes, then back to 3200 for a long time then to 4000 then maybe 4400 then back to 4000 then 3100 for a bit. It was just all over the place, not in a fast way but it would hold for a min to 10 min like that to sometimes 30 seconds. It did this for 65 miles. Go to my destination (I still go the boat to do 35MPH) and didn't have enough tools to do a full diagnosis but all weekend long it did that. I even filled the tank with more fuel, 89 with Valvtec.
On Sunday on the way home, Started out the same issues with that same bad motor for 30 min then the other GOOD motor acted up. It was starving for fuel going from 4000 to 3000 to 2500 to 3000 to 2000 to 3000 RPM'sl. I had to have my gf sit on the back pumping that bulb for 20 min, even stopped, turned off the motor, pump the bulb to full hard 3 times before the good engine acted normal for the rest of the 1.5 hour drive home.
When all this was acting up the bad motor was fluctuating from 2000 to 3200 and I think it was because the other motor wasn't pushing like it use to. Once I got my "good" motor to stay alive / get back to normal, I set that to 4000 and the other one (original bad motor) to 3000 and cruised home. Right outside my home I played with it to see if the "Problems" went awa. Open her up full throttle and good motor went to 5200 bad motor did not even come close, 4000 Max.
So here are some of my thoughts and I would love suggestions or ideas what to fix / check please.
1) Bad fuel pump. Possible for both engines but deff bad on that one. Are these a mechanical or electric fuel pump? Is there a low pressure and high pressure pump?
- Reason I think its a weak pump is that originally it wouldn't hit 5000 now it barely hits 4000 with a added fuel filter. Maybe the restriction of that fuel filter is making it harder to pump the fuel to the motor?
2) Clogged fuel filters. I will change my Water Separator, but any other filters to check? Is there a filter before the injectors? I know Yamaha has a VST (or something like that) filter before the injectors that are known to clog and cause issues like this. Does mercury?
3) Bad / Clogged injectors. I am thinking of sending them out at the end of the season any ways but could it be just those?
Again, if anyone had this issue, seen this issue, fixed this issue, or just might have some other ideas please let me know. I greatly appreciate that!
Last edited by srdrago; 08-29-2016 at 07:43 AM.
Gold Member
