Varnish removal in rubber fuel lines

[MMarty]

Hi All, I just got a 5HP Mercury from I believe 1993 (Can't find Ser# boat & trailer are '93). There is a lot of varnish in the bottom of the onboard fuel tank (Polyethylene- High or Low density?). Research shows Methyl Ethyl Ketone and Acetone to be the best solvents for loosening/ dissolving the varnish with moderate reaction with the plastic tank. However, there are several small rubber fittings in the gas line that are OEM and are exorbitantly priced. I bought a new OEM carb cheap, less than the price of an OEM rebuild kit, to avoid a rebuild. Any thoughts on how to clean the inside of the rubber fittings. Simple Green and Lestoil are names I have seen . Thanks for your help.

 

[Willyclay]

Welcome to the forum. I am a fan of Simple Green but for more difficult cleanings I like Purple Stuff. Good luck with your project!

 

[Commander_47]

That bad thing about purple stuff is that you are putting water based detergent in your fuel system.

Acetone will burn in your motor. I would clean out the tank really well with acetone, and you can use cheap spray carb cleaner. It works really good as well.

Chances of damaging the O rings with carb cleaner or acetone is remote. I would be more concerned with the age of the rubber. If it is cracked at all, the lines and O rings probably need replacing. I mean, after all, you are coming up on 28 year old rubber!!!!!!!!

If you have a rebuilt carb and get it all back together, just run it with clean gas and see what happens. You can always tray running a 1/4 tank of gas with a little acetone added, and or add a tablespoon of Marvel mystery oil.

If you flex the rubber fuel lines, more than likely the varnish with crack and flake off inside the line. If you can flush it with carb cleaner it should clean up really well.

If you crush up the varnish in the lines, and don't dissolve it before running the motor, you risk plugging your new carb. Not a big problem, but definitely a PITA.

 

[Sprig]

Rubber does not last indefinitely, it has a shelf life. Your rubber hoses are about 30 years old. Even though expensive it’s time to replace rubber hoses and fittings. If nothing else that should be considered preventative maintenance.
If the gas tank is a portable tank you may want to just replace that also. You can try to clean it and you may be fine but for me when it comes to boat motor maintenance I go the extra step and expense to ensure problem free safe boating experience.

 

[dingbat]

E10 is the best fuel system cleaner bar none.
Change the fuel lines.... fuel lines are actually two hoses in one with a 10 year life expectancy.

The liner which is in contact with the fuel and thr outer cover which protects the liner from external damage.

By the time the outer cover dry rots and gets hard the liner has long since been compromised and the fuel starts to permeate the cover.

 

[MMarty]

To all the respondents, thank you for all of your input so far.
I got around to doing some PM to the engine:
1] the fuel in the tank was reduced to approximately 4 ounces of a nasty smelling viscous liquid. I removed the tank and emptied it into a milk jug. Then I rinsed the tank with acetone two times. There were no solids at all in the tank except for a spiral cut of polyethylene 7/8" Diam. that stopped the flow of acetone to a trickle. It could have easily prevented proper fuel flow. The spark plug did not appear to have more than 20 hours of use as it practically new.
2] The fuel cap is defective, rubber is stiff, the plastic dangling retainer was fragile and broke-new one ordered.
3] Interestingly, this motor has a switch over valve (13) that allows you to attach and run an external tank. I used Seafoam and hard bristle pipe cleaners and believe I got a majority of the gas goo out. Surprisingly the fuel lines were clean rearward from the filter(17) and Connector (21). #21 appears to be a check valve though the part list calls it a connector to prevent backflow of gas from the internal tank as it is in the line for the external fuel feed. Bought a new one.
The only appreciable gas goo was in the elbow (12) at the bottom of the fuel tank, again Seafoam and bristle cleaners. The fuel lines were still quite pliable.
Once the filter and connector/ check valve get here I will ascertain the condition of the fuel line to the carb. Hopefully that is free of gas goo. And If I'm really fortunate the carb will only need Gumout and Seafoam treatment instead replacement. Here's keeping my fingers crossed.
There is also a crankcase ventilation tubing that runs directly to the cylinder head that I need to check for serviceability.
Thanks again for your input, Marty