Manual fuel pump restrictions?

[tank1949]

I have about a 2' foot vertical drop from my fuel tank to Chevy 350 with manual fuel pump. However, the horizontal length of the line is about 6'. Fuel comes from tank into a tank selector switch manifold and into a water/fuel separator. From there it goes to fuel pump. Is this horizontal length too long???

 

[Chris1956]

I presume the fuel tank is 2' lower than the engine? That seems unusual. I would expect the tank to be no more than 1 foot lower as most sterndrive boats have the engine sitting on 4-6" stringers molded to the bottom of the hull. Most fuel tanks sit on the base of the hull as well.

I would not think the 2' lift or 6 foot of fuel line is a problem, as long as it is 3/8 ID. If you are having fuel delivery issues, the antisiphon valve, water separator, fuel selector or any other filters could be the issue.

Also, some of those GM mechanical fuel pumps have a porous stone filter on the top of the fuel pump. If you have that, has it been changed? Some carbs also have a paper filter where the fuel line connects. That should be changed periodically.

The water separator should be dumped into a clear container so you can see dirt, rust and water. Replace it once/year.

My SeaRay also had a filter on the fuel pickup pipe. That got partially clogged after some years. You needed to pull the pickup out of the tank and unscrew the aluminum pipe to expose the filter.

Have you run with the selector valve for a while, or is it new?

 

[Scott06]

Are you having an issue with it and is it the factory set up ? Although it sounds a little longer and higher. My set up is about 4 ft horizontal and maybe 18" vertical maybe 24" if you count to bottom of tank.

This is with an electric pump - no idea if suction lift of pump is different than mechanical pumps.

Would think a mechanical pump would have no issue with what you outline. If you call the pump manufacturer or look at specs not sure if they publish a suction lift spec.

 

[cyclops222]

Confusion
He has a tank 2' higher than engine ? A selector valve ?
So is this higher tank sitting on the floor of the boat for added range if main tank goes empty ?

 

[tank1949]

Thanks to all. I will examine for additional inline filters!!! Their addition would seem to be too redundant, but I am not a marine engineer. The pickup tube screens have been removed. I discovered that potential problem. 2' is vertical DROP (best that I can tell) from fuel separator to FP. Seperator and fuel tank selector are nearly parallel to tank's top and only inches from tank. Fuel draw from inside tank to its bottom is about 18". Fuel/water separators are new.

 

[Scott Danforth]

Is this horizontal length too long???

NO

a similar mechanical pump in a 1972 impalla wagon had to pull the fuel 22 feet from the tank thru smaller ID fuel line, as well as pull the fuel vertical up about 1-1/4 feet.

the mechanical pump in good condition will suck in the walls of the tank a bit prior to starving the motor for fuel

My boat with the old motor had to pull the fuel aft 8 feet, as well as having the tank about 2 feet above the pump. I now have an electric pump mounted about 5 feet aft of the pickup and push it the last 3 feet.

what issue are you having?

 

[tank1949]

NO

a similar mechanical pump in a 1972 impalla wagon had to pull the fuel 22 feet from the tank thru smaller ID fuel line, as well as pull the fuel vertical up about 1-1/4 feet.

the mechanical pump in good condition will suck in the walls of the tank a bit prior to starving the motor for fuel

My boat with the old motor had to pull the fuel aft 8 feet, as well as having the tank about 2 feet above the pump. I now have an electric pump mounted about 5 feet aft of the pickup and push it the last 3 feet.

what issue are you having?

We were not getting fuel to pump. We believe we have it all corrected now, but I want to be sure the fuel draw length will not be an issue later on. We will check for inline filters today. Just to be sure....

 

[Scott Danforth]

check for leaks at the anti-siphon

 

[tank1949]

check for leaks at the anti-siphon

used boat and didn't come with them. THX . The fuel selector labeling was not pointing to the correct fuel lines. We finally figured it out. Getting plenty of fuel, so far!