Water in Fuel

[twainiac]

Hello everyone, I need some help concerning my fuel system. I rebuilt the Mercruiser 140 engine of a 1982 Mark Twain runnabout several years ago. Engine ran perfectly for one and half seasons then I began having problems. Vapor locking when hot and water in fuel system. Aluminum fuel tank was professionally cleaned and sealed, all new fule lines installed, three in line fuel filters/water separators. Got fed up with it, parked it for a couple of years and recently decided to do a full restoration. Never had much sense!

I have alot of experience as an auto and aircraft mechanic but this is my first boat project.

Any ideas?

Thanks, Bill

 

[dubs283]

Re: Water in Fuel

vapor lock can occur when running pump 87 octane (oxegenated) gas esp on hot days. if you can get it use non-oxy (no ethanol) gas 91/92 octane.

ethanol, being alcohol, does attract water when the fuel sits for a long time

drain all old fuel, change all fuel filters, add dri-fuel to tank, and also check the o-ring on the fuel fill cap. if ruptured will allow rain water into tank

 

[Bondo]

Re: Water in Fuel

and water in fuel system. Aluminum fuel tank was professionally cleaned and sealed, all new fule lines installed, three in line fuel filters/water separators

Ayuh,... Does the Tank Vent line, loop Up,+ then down to the tank,..??

If Not,... That's probably where the Water is coming from...

 

[twainiac]

Re: Water in Fuel

No loop in tank vent, runs straight down to tank. Assumed this was factory config, good suggestion. Can a check valve be used in tank vent?

Not familiar with dri-fuel? Similar to fuel stabilizer?

Thanks,

 

[rbh]

Re: Water in Fuel

if there is an O ring on the filler cap it could be cracked or dried out replace,
and I would think no to the inline check valve.
rob

 

[Bondo]

Re: Water in Fuel

Can a check valve be used in tank vent?

Nope,... It needs to be Free to Breathe...