DeepBlue2010
Lieutenant
- Joined
- Aug 19, 2010
- Messages
- 1,305
Hello everyone, I had this problem a week ago with my boat (1996 Bayliner 2855 with Mercruiser 7.4L & Bravo 3). I solved the problem but thought I will write up the experience as it might help someone someday.
The problem started when I was on my way back to the marina from a fishing trip (about 11 miles away), when I tried to pick up some speed and plane and once I exceeded 2000 RPM, the RPM dropped suddenly but the engine did not stall.
I kept trying to get on plane with no avail. I had to head back to the marina on about 2000 RPM which pushes the boat @7.0 nm. The boat worked fine on these parameters with no sign of trouble at all but lost power again and again every time I tried to push her on plane.
At home, I did some research and read some horror stories about people who spent some $9K only to find out that a stupid flapper in the Y pipe has deteriorated and blocked the exhaust passage. Some others indicated the carburetor or the gas pump. Long story short, I did not find a troubleshooting procedure that help me trace the problem logically.
I started to write down what I know about my boat (this is my 3[SUP]rd[/SUP] year with it)
I contacted a friend of mine and ran it by him and he pointed to the possibility of water in my gas tank. Also one result of the google search came up with this possibility so I thought letâs give it a try and see.
I removed my fuel filter and emptied it in a transparent container and here it was, a clear separation between about 8 or 10 oz of water (on the bottom) and fuel on top.
Here goes new filter, added water disbursement agent enough to treat double the capacity of my tank (which was full) and out for sea trial. Worked fine and I was able to plane for few miles and suddenly the RPM dropped down again and I had to idle back to the marina; thankfully only few miles away this time.
Back to the dock and square one again, I started to think that there is maybe more water in the tank than I thought. I inspected the O ring on the filling cap and it was in a very bad condition. We had a very strong rain storm in Seattle the whole week and it is very possible that the water found its way in through the unsealed filling cap.
I replaced the O-ring while I am at it and planning on doing so periodically from now on. I also bought a hand pump rated for gasoline and removed the sending unit from the middle on the gas tank. I taped the suction hose to a small diameter PVC pipe to ensure that the hose will make it straight to the bottom of the tank. I also asked the marina to raise the front of the boat a little (I am on a dry slip).
I pumped out a couple more ounces of water but it wasnât nearly enough to explain the second testâs failure. I was working under the assumption that when the boat planes and the gas started to shift in the tank, the pickup tube is picking up mostly water but the couple of ounces I pumped out donât support this theory.
I started to talk to some local marinas and they suggested draining all the fuel and start over, some of them assured me that the fuel was bad, some said I ruined the fuel by adding the water disbursement agent. The cost of pumping out the tank and refill was approaching $1000. Ironically the cost of recycling fuel is double the cost of buying it.
Honestly, I never bought this theory and I felt I am being taken for a ride simply because neither this theory of bad fuel nor any of the people who are advocating for it can explain to me why a bad fuel is not bugging the engine down at any RPM less than 2000
I was about to give up and bite the bullet when an idea came to my mind. I was focusing only on the relationship between the geometry of the fuel/water in the tank changing as I tried to get on plane but I ignored the rate of flow of this fuel as the engine demands more and more of it at high RPM. Once the word flow came to my mind, I remembered that I installed Garmin Fuel Flow sensor GFS10 and the filter that came with it early last season. If this sensor is blocked with water or crud, it will restrict the flow at high RPM also.
I tried to find a replacement for this filter from Garmin with no luck but the filter was identical to of the shelf one. Frankly, I think it is what Garmin uses; they only painted it black.
I installed the new filter and went for sea trial. The boat worked as it used to. I had no problem getting and staying on plane. Next day I went fishing â about 22 nm round trip â and the boat continued to work fine.
I hope this information will help someone in the future. Enjoy the rest of the season and stay safe.
The problem started when I was on my way back to the marina from a fishing trip (about 11 miles away), when I tried to pick up some speed and plane and once I exceeded 2000 RPM, the RPM dropped suddenly but the engine did not stall.
I kept trying to get on plane with no avail. I had to head back to the marina on about 2000 RPM which pushes the boat @7.0 nm. The boat worked fine on these parameters with no sign of trouble at all but lost power again and again every time I tried to push her on plane.
At home, I did some research and read some horror stories about people who spent some $9K only to find out that a stupid flapper in the Y pipe has deteriorated and blocked the exhaust passage. Some others indicated the carburetor or the gas pump. Long story short, I did not find a troubleshooting procedure that help me trace the problem logically.
I started to write down what I know about my boat (this is my 3[SUP]rd[/SUP] year with it)
- Last year I ran a compression test and it was to spec
- New plugs
- No signs of trouble with the carburetor
- New fuel pump (this season)
I contacted a friend of mine and ran it by him and he pointed to the possibility of water in my gas tank. Also one result of the google search came up with this possibility so I thought letâs give it a try and see.
I removed my fuel filter and emptied it in a transparent container and here it was, a clear separation between about 8 or 10 oz of water (on the bottom) and fuel on top.
Here goes new filter, added water disbursement agent enough to treat double the capacity of my tank (which was full) and out for sea trial. Worked fine and I was able to plane for few miles and suddenly the RPM dropped down again and I had to idle back to the marina; thankfully only few miles away this time.
Back to the dock and square one again, I started to think that there is maybe more water in the tank than I thought. I inspected the O ring on the filling cap and it was in a very bad condition. We had a very strong rain storm in Seattle the whole week and it is very possible that the water found its way in through the unsealed filling cap.
I replaced the O-ring while I am at it and planning on doing so periodically from now on. I also bought a hand pump rated for gasoline and removed the sending unit from the middle on the gas tank. I taped the suction hose to a small diameter PVC pipe to ensure that the hose will make it straight to the bottom of the tank. I also asked the marina to raise the front of the boat a little (I am on a dry slip).
I pumped out a couple more ounces of water but it wasnât nearly enough to explain the second testâs failure. I was working under the assumption that when the boat planes and the gas started to shift in the tank, the pickup tube is picking up mostly water but the couple of ounces I pumped out donât support this theory.
I started to talk to some local marinas and they suggested draining all the fuel and start over, some of them assured me that the fuel was bad, some said I ruined the fuel by adding the water disbursement agent. The cost of pumping out the tank and refill was approaching $1000. Ironically the cost of recycling fuel is double the cost of buying it.
Honestly, I never bought this theory and I felt I am being taken for a ride simply because neither this theory of bad fuel nor any of the people who are advocating for it can explain to me why a bad fuel is not bugging the engine down at any RPM less than 2000
I was about to give up and bite the bullet when an idea came to my mind. I was focusing only on the relationship between the geometry of the fuel/water in the tank changing as I tried to get on plane but I ignored the rate of flow of this fuel as the engine demands more and more of it at high RPM. Once the word flow came to my mind, I remembered that I installed Garmin Fuel Flow sensor GFS10 and the filter that came with it early last season. If this sensor is blocked with water or crud, it will restrict the flow at high RPM also.
I tried to find a replacement for this filter from Garmin with no luck but the filter was identical to of the shelf one. Frankly, I think it is what Garmin uses; they only painted it black.
I installed the new filter and went for sea trial. The boat worked as it used to. I had no problem getting and staying on plane. Next day I went fishing â about 22 nm round trip â and the boat continued to work fine.
I hope this information will help someone in the future. Enjoy the rest of the season and stay safe.
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