Engine Question

secondcurve · 10-13-2008, 06:59 PM

I'm looking at buying a small pontoon boat. The ones I am looking at are around 16 feet and almost all of them are powered by Mercury 25 Big Foot 4-strokes. This boat won't be on the big Lake so the relatively small size will work for my needs. The question I have is all of the used motors before 2005 don't utilize fuel injection. Thus, from what I gather they are prone to getting water in the gas if the gas sits too long without use. Can anyone comment of their experiences with or without the fuel injection on the Mercury 25 horse motors? Thanks

Audiofn · 10-13-2008, 09:31 PM

I have never noticed it to be any worse with a carb motor then Fuel injected. In fact I would assume that the fuel injection would be worse for getting water in the fuel. The typical 16 footer would use the "bounce around" tanks. Those are easy to keep water free. Just make sure that there is a water seperator in line.

NBR · 10-14-2008, 03:39 PM

I believe the water would have to come from condensation and is not connected with FI or carburation. Keep the tank full but I doubt if it is a serious issue. I think metal tanks are much more prone to condensation than plastic ones. A little "Sta-Bil" also helps.

Seeker · 10-14-2008, 09:29 PM

I would go with FI if possible; just seems more reliable to me. There is no difference in getting condensation in a FI or non FI engine. As mentioned above a metal tank might be a little more conducive to condensation but if it's a 6 gallon one you can easily get rid of the water.

Grady223 · 10-15-2008, 08:22 AM

The solution to the water in the gas problem is to buy non ethanol gas. The subject of various other posts. You can only get it at some marinias on the Lake. that will cost more but is well worth the extra cost (damaged engine). Do not fill your boat at a gas station.

secondcurve · 10-15-2008, 07:01 PM

Quote:

Originally Posted by NBR

I believe the water would have to come from condensation and is not connected with FI or carburation. Keep the tank full but I doubt if it is a serious issue. I think metal tanks are much more prone to condensation than plastic ones. A little "Sta-Bil" also helps.

NBR:

This is exactly what the mechanic said. When the motor heats up and then cools down condensation accumulates inside. I'm not sure why Fuel Injection is not prone to this problem, but according to this knowledgeable guy it is. He told me that the way I should handle the carb motor is to take any gas left in the plastic tank at the end of the weekend and pour it into my car gas tank. Then I should run out the motor until it stalls. Does anyone out there use a 4-stroke 25 horse Mercury with a carb? I'd be curious to hear about your experience.

Audiofn · 10-15-2008, 08:31 PM

There should be no difference between a 2 and a 4 stroke with a carb. The fuel delivery is esentially the same. I have run 2 stroke carb motors for a while with very little issues.

I disagree with running them dry. The problem that I have seen with the new fuel is that as it dries up it powders/chocks up and clogs things. I would think that running it dry would make things worse. There will still be fuel left in the carbs even after it dies. If you leave lots of fuel in the carbs I would think that it would be less likely to have this issue. What I see is that the people that use their boats have less problems and the ones like me lately (building a house is taking all my time) are having issues. Water in fuel from everything that I have ever read will effect fuel injection worse then a carberator. I would not worry about carb vs. fuel injection just buy what you think is the best deal and use the heck out of it

10-13-2008, 06:59 PM	#1
secondcurve Senior Member Join Date: Jan 2005 Posts: 2,118 Thanks: 1,329 Thanked 559 Times in 288 Posts	Engine Question I'm looking at buying a small pontoon boat. The ones I am looking at are around 16 feet and almost all of them are powered by Mercury 25 Big Foot 4-strokes. This boat won't be on the big Lake so the relatively small size will work for my needs. The question I have is all of the used motors before 2005 don't utilize fuel injection. Thus, from what I gather they are prone to getting water in the gas if the gas sits too long without use. Can anyone comment of their experiences with or without the fuel injection on the Mercury 25 horse motors? Thanks

10-13-2008, 09:31 PM	#2
Audiofn Senior Member Join Date: Sep 2004 Location: Bedford, MA/Naples, ME Posts: 162 Thanks: 3 Thanked 2 Times in 2 Posts	I have never noticed it to be any worse with a carb motor then Fuel injected. In fact I would assume that the fuel injection would be worse for getting water in the fuel. The typical 16 footer would use the "bounce around" tanks. Those are easy to keep water free. Just make sure that there is a water seperator in line.

10-14-2008, 03:39 PM	#3
NBR Senior Member Join Date: Apr 2004 Location: Bristol Posts: 119 Thanks: 0 Thanked 19 Times in 15 Posts	I believe the water would have to come from condensation and is not connected with FI or carburation. Keep the tank full but I doubt if it is a serious issue. I think metal tanks are much more prone to condensation than plastic ones. A little "Sta-Bil" also helps.

10-14-2008, 09:29 PM	#4
Seeker Senior Member Join Date: Nov 2007 Location: Effingham Posts: 408 Thanks: 37 Thanked 19 Times in 15 Posts	I would go with FI if possible; just seems more reliable to me. There is no difference in getting condensation in a FI or non FI engine. As mentioned above a metal tank might be a little more conducive to condensation but if it's a 6 gallon one you can easily get rid of the water.

10-15-2008, 08:22 AM	#5
Grady223 Senior Member Join Date: Apr 2004 Location: New Hope, PA & Barndoor Island Posts: 465 Thanks: 93 Thanked 24 Times in 18 Posts	The solution to the water in the gas problem is to buy non ethanol gas. The subject of various other posts. You can only get it at some marinias on the Lake. that will cost more but is well worth the extra cost (damaged engine). Do not fill your boat at a gas station.

10-15-2008, 08:31 PM	#7
Audiofn Senior Member Join Date: Sep 2004 Location: Bedford, MA/Naples, ME Posts: 162 Thanks: 3 Thanked 2 Times in 2 Posts	There should be no difference between a 2 and a 4 stroke with a carb. The fuel delivery is esentially the same. I have run 2 stroke carb motors for a while with very little issues. I disagree with running them dry. The problem that I have seen with the new fuel is that as it dries up it powders/chocks up and clogs things. I would think that running it dry would make things worse. There will still be fuel left in the carbs even after it dies. If you leave lots of fuel in the carbs I would think that it would be less likely to have this issue. What I see is that the people that use their boats have less problems and the ones like me lately (building a house is taking all my time) are having issues. Water in fuel from everything that I have ever read will effect fuel injection worse then a carberator. I would not worry about carb vs. fuel injection just buy what you think is the best deal and use the heck out of it