Replacing fuel lines

[Butt Ugly]

Been having a fuel problem in the boat. Finally got to the bottom of things and figured out where the problem lies. The rubber fuel lines are nearly 30 years old, and look to be deteriorating. Amazing the junk and particles that came out when I drained the line into a jar.

I was told that the line running from the fuel pump to the carb should be hard line. Should this line be copper or steel, and does it make any difference? I have some copper laying about that I could flare if it's ok to use.

Looking deeper into the problem, I siphoned out some fuel from the tank, and found more junk. I was straining it as I siphoned through a coffee filter, just to see how much crap there was. Lots would be an understatement. So I strained out the whole tank, and then removed it from the boats bow. As I swished and poured out the last few ounces, I was astonished at how much crap there was in the tank.

I called a shop to have the tank cleaned, and being aluminum, he said all he could do is wash it out, (chemical cleaning is too harsh for aluminum) and suggested if I wanted to save a few dollars, I could do the same with a powerwasher, then let it air dry. Any other suggestions or information I need to know to do this properly?

Hopefully I can get this all done for the weekend and get back to fishing!

 

[danthewire]

Take a good look inside that tank if it's 30 years old.I had one in the old boat and it was rotting from the inside out.Look for tiny pinholes.As to running a rubber line from the fuel pump to the carb,I personally would never do it.It is over kill but we always ran steel braided line between the two.And no I did't use the fancy aniodized fittings.I hope that you're running a filter,separator on the line.DAN

 

[Tanglefoot]

I'd stay away from rubber on top of the engine. My fuel lines seem to be steel. I like the idea of braided steel; aircraft engines have these and they do away with vibration failure. Don't go cheap when dealing with fuel distribution. Fuel explosions are quite spectacular[V]and deadly.

Tom

 

[Butt Ugly]

Great, I'll definately put the boat back to hardline over the engine. I don't need no fire or explosions, and as a firefighter, it sure wouldn't look to good!

Looking inside the tank, it looks pretty nice and being aluminum, I don't see any corrosion, but there sure is alot of muck in the bottom of it. I've removed all the fittings and will try to pressure wash all the gunk out tomorrow.

Don't know where else I might add any more filters if it's really even necessary. From the tank to the back of the boat there is a fuel filter/separator, which then runs to the fuel pump with another filter built in it, and finally from the fuel pump to the carb which has a third filter at the fuel inlet fitting. The only place I could think would be beneficial would be some kind of strainer on the fuel pickup line inside the tank.

Appreciate the replys! The mercruiser manual has been a great help with most the things I've needed to work on, but nothing beats the experience from many of the members here.

 

[Butt Ugly]

Got the boat back in the water last night! I am amazed at what problems this has fixed.

The reason I needed to rebuild the fuel system was that the boat would run for a minute or two, then die like it was out of fuel. After about 5 minutes it would run again for another minute or two before dying again. This just kept repeating.

All lines were replaced, tank cleaned, and all filters replaced again. Now she runs great and the fuel problem is gone. Basically, there was so much crap in the tank and the lines that a blockage was heavily restricting the fuel flow. The boat would run the gas out of the lines up to the blockage then crap out. After a few minutes which allowed enough gas to trickle through the blockage and fill the lines again, it would run until it had used it up and repeat.

The engine is now getting the fuel it requires to run efficiently. It has even solved another problem I was wrestling with, which was trying to find a prop to get the proper WOT rpms. With a good clean fuel systems working properly now, when I went out for the sea trial, first thing I noticed was that my idle rpm had jumped from about 700 to 1500! I guess the engine likes getting an unresticted fuel flow. The motor doesn't stumble at idle anymore either, another problem solved.

I couldn't get the boat to run up at WOT yet, because it was just too lumpy out there last night, but I did push it up to 3600rpm before the boat was leaping off the big swells, and the rpms were still rising and I still had more throttle left in it. Can't wait for a flat day to see what I'll get her to peg out at now. Will be nice to be able to properly match a prop to the boat now, and it's no wonder the pitch changes weren't giving me the increase or decrease in rpm that it should have.

All in all, it wasn't a difficult job, just a pain in the a$$, but the rewards sure were worth it.