Is There Another Way to Install a Fuel Pump? (Gasoline/Petrol)

[rslifkin]

Thinking about it more, a day tank is probably the right answer. It can be fairly small. Just have a pump to transfer fuel to it from the main tanks (which could be automated with float switches). The day tank being at explosives locker level should mean you wouldn't need any additional pumps to the engines, just something to feed fuel up to the generators (I'd just put a pump on each unit for that).

[Chotu]

I have 2 outboards, in wells, approximately 25ft apart from each other.

I have 2 generators, much higher up. Roof mounted.

Need to fuel all of these from the main tanks.

[Chotu]

OK, I think this thread will be an evolution. I’m going to try a couple things first because all of that is a lot of extra work.

First up: just use the 120” lift pump with the same setup I have now.

It’ll pull up from the tanks and can definitely push to the generators and outboards.

If that works, great. If not, time to explore some of the other ideas here

[Scubaseas]

Originally Posted by Chotu

I have 2 outboards, in wells, approximately 25ft apart from each other.

I have 2 generators, much higher up. Roof mounted.

Need to fuel all of these from the main tanks.

You have, not to be obtuse, two gasoline powered generators that are approximately 12' to 15' vertically above the fuel tank pick up tube opening?

I'd worry more about how you are going to feed the generators than I would how to get fuel to the engines. Check the specs or installation manual for the generators but they probably have to be less than 36" above their fuel tanks.

[Scubaseas]

If your roof mounted generators share a fuel supply line with the outboards how do you keep the outboards from sucking air into the lines from the generator supply lines? A solenoid or do you manually open/close a ball valve?

[AKA-None]

So let’s review your requirements
At least a 60 inch lift
Should not be pressurized
Engines need some minimum of fuel pressure
Minimize the pressurized fuel lines
Pressurized fuel lines can’t be inside
Any part that pressurized fuel must shut off if there is no call for fuel

Did I miss anything?

So you need to lift the fuel and then send pressurized fuel to an engine

A pump that can lift fuel may or may not meet the pressure requirements of the engine

You may need two pumps one to lift and one to pressurize

Thoughts?

[Chotu]

Originally Posted by Scubaseas

You have, not to be obtuse, two gasoline powered generators that are approximately 12' to 15' vertically above the fuel tank pick up tube opening?

I'd worry more about how you are going to feed the generators than I would how to get fuel to the engines. Check the specs or installation manual for the generators but they probably have to be less than 36" above their fuel tanks.

I was going to pump fuel up there when they are running. No?

Can’t these pumps push fuel like crazy? It’s just that they are limited in pulling fuel?

[Chotu]

Originally Posted by Scubaseas

If your roof mounted generators share a fuel supply line with the outboards how do you keep the outboards from sucking air into the lines from the generator supply lines? A solenoid or do you manually open/close a ball valve?

The outboards, at absolute wide open throttle, can’t consume more than 6 gallons of fuel per hour. With both on ar the same time. The pumps are like 30 GPH.

If both generators are on and loaded up with air conditioning or a resistive heating element , together, with both on, they can’t consume more than 1GPH.

So max consumption is 6GPH on the outboards and 1GPH on the generators.
Fuel pumps are 30GPH.
To me, it seems like there will be way, way more fuel than necessary to keep up. No?

And actually for more efficiency, I typically run only one outboard at a time. So 2.5GPH on the outboard (at 7knots) is typical.

I have yet to hook the generators up to the fuel system. Getting the air conditioning working for the coming heat is the reason I’m recommissioning the fuel system. So I’m trying to hook them all up in a permanent fashion. I had been using a regular outboard fuel tank on the roof with one larger generator for the past 5-6 years.

[AKA-None]

Originally Posted by Chotu

I was going to pump fuel up there when they are running. No?



Can’t these pumps push fuel like crazy? It’s just that they are limited in pulling fuel?

You can get pressure regulated pumps or even add a regulator

My rv tank is 6 inches deep
The fuel goes up then about 4 ft to a filter then to a pump that pushes at 18 or so 20 ft including up about 2 ft then to a regulator that drops it to 5 psi to the carb.

I got the regulator at summit engineering and it can drop to 0 if I want the pump itself if 20 psi open pressure and 80gal hr
But the regulator will manage it down to what the engine requires.

So even if a pump can push more than you need you can regulate it down.

Your requirements are to such the fuel up 60 inches and then maybe use a second pump that pushes what you need

A fuel pump that can pull up that distance and then push to the engine will likely need something to regulate it back down

Make sense?

[Scubaseas]

Originally Posted by Chotu

The outboards, at absolute wide open throttle, can’t consume more than 6 gallons of fuel per hour. With both on ar the same time. The pumps are like 30 GPH.

If both generators are on and loaded up with air conditioning or a resistive heating element , together, with both on, they can’t consume more than 1GPH.

So max consumption is 6GPH on the outboards and 1GPH on the generators.
Fuel pumps are 30GPH.
To me, it seems like there will be way, way more fuel than necessary to keep up. No?

And actually for more efficiency, I typically run only one outboard at a time. So 2.5GPH on the outboard (at 7knots) is typical.

I have yet to hook the generators up to the fuel system. Getting the air conditioning working for the coming heat is the reason I’m recommissioning the fuel system. So I’m trying to hook them all up in a permanent fashion. I had been using a regular outboard fuel tank on the roof with one larger generator for the past 5-6 years.

GPH is a red herring for this kind of planning. You do not need to try and match your pumps to you expected max GPH of the outboards and generators. Not a problem if your pump is a higher gph than needed at WOT.

You DO need to consider that the generators can not pick up or lift fuel more than about 36". Same with your outboards. A mechanical lift pump can pull about 36" and usually not much more. Check the specs on your units. If your tanks are in the hull and your generators are on the coach roof you have a dry lift of what? 10' or 11'? If you build a day tank on the deck the generators are still what, 6' above that day tank? You may have to put a day tank on the roof too? The hard part looks to be the pump having to be within 12" and no more than 48" of hose for a pressure fuel supply. Which makes a day tank start to look attractive.

If you hook a fuel line up to the generator and you run the outboards and the fuel line is shared, you may pull air back through the generator fuel line. Even if the generator is throttle body injection, there is still a vapor tank on it that vents to air and may pull air into the fuel line. Same if it has a carburetor. It's not likely but it may be possible. So don't share fuel lines at different levels.

If you put just a day tank on the roof beware of fuel siphoning to the outboards unless you have a line solenoid or a valve. Sounds like you have been using a day tank on the roof to run the generators.

[Scubaseas]

Originally Posted by AKA-None

You can get pressure regulated pumps or even add a regulator

My rv tank is 6 inches deep
The fuel goes up then about 4 ft to a filter then to a pump that pushes at 18 or so 20 ft including up about 2 ft then to a regulator that drops it to 5 psi to the carb.

I got the regulator at summit engineering and it can drop to 0 if I want the pump itself if 20 psi open pressure and 80gal hr
But the regulator will manage it down to what the engine requires.

So even if a pump can push more than you need you can regulate it down.

Your requirements are to such the fuel up 60 inches and then maybe use a second pump that pushes what you need

A fuel pump that can pull up that distance and then push to the engine will likely need something to regulate it back down

Make sense?

There are pumps that can easily push 12', there are pumps that can easily lift or pull fuel up 12'. The problem is ABYC codes.

"In reviewing some ABYC requirements (thanks BoatPoker), I see one I can’t meet at all.

“ 24.15.7 If used, electric fuel pumps shall be independently supported and located within 12 inches (305 mm) of the engine with a maximum delivery hose length of 48 inches (1.22 m).”..."

This does not apply to transfer pumps. If you put a day tank on the roof with a lift pump (Facet dura-lift 40303, 4.25 to 6.25PSI, 33gph) you can solve all the issues. You could use a pusher or a puller pump if using it for fuel transfer. If you want no pressure lines in the boat use a puller or lift type pump.

[Chotu]

Ok, this is where my thinking is breaking down. I think you found it.

I am picturing the whole thing like every other type of plumbing.

If you have a kitchen sink, a garden hose outside, a bathroom sink upstairs and a tub/shower upstairs in a house, one pump provides all the pressure to all the outlets and you can turn them on at the same time too.

Why doesn’t a fuel system work the same way as every other type of plumbing including boat freshwater plumbing??

Why does my generator need to pull anything at all up to itself when it’s connected to a positive pressure plumbing system? If I pull the fuel line off the generator with the fuel pump operating, it’ll spray all over the roof, right?

So why is there any concern about the mechanical fuel pump in the generator lifting anything ?

Along the same lines of reason, how can an outboard steal fuel and suck air into the system from the generator fuel line when both are under positive pressure?

My brain says the only way that could ever happen is if the pump providing the positive pressure can’t keep up with the GPH of the system and the system pressure goes negative.

I’m lost. I can’t understand the dynamics of what you are suggesting can happen.

Where am I going wrong in my plumbing thinking? It all works like I picture for house and freshwater system in boats. Why not for fuel?

Originally Posted by Scubaseas

GPH is a red herring for this kind of planning. You do not need to try and match your pumps to you expected max GPH of the outboards and generators. Not a problem if your pump is a higher gph than needed at WOT.

You DO need to consider that the generators can not pick up or lift fuel more than about 36". Same with your outboards. A mechanical lift pump can pull about 36" and usually not much more. Check the specs on your units. If your tanks are in the hull and your generators are on the coach roof you have a dry lift of what? 10' or 11'? If you build a day tank on the deck the generators are still what, 6' above that day tank? You may have to put a day tank on the roof too? The hard part looks to be the pump having to be within 12" and no more than 48" of hose for a pressure fuel supply. Which makes a day tank start to look attractive.

If you hook a fuel line up to the generator and you run the outboards and the fuel line is shared, you may pull air back through the generator fuel line. Even if the generator is throttle body injection, there is still a vapor tank on it that vents to air and may pull air into the fuel line. Same if it has a carburetor. It's not likely but it may be possible. So don't share fuel lines at different levels.

If you put just a day tank on the roof beware of fuel siphoning to the outboards unless you have a line solenoid or a valve. Sounds like you have been using a day tank on the roof to run the generators.

[rslifkin]

Originally Posted by Chotu

Ok, this is where my thinking is breaking down. I think you found it.

I am picturing the whole thing like every other type of plumbing.

If you have a kitchen sink, a garden hose outside, a bathroom sink upstairs and a tub/shower upstairs in a house, one pump provides all the pressure to all the outlets and you can turn them on at the same time too.

Why doesn’t a fuel system work the same way as every other type of plumbing including boat freshwater plumbing??

Why does my generator need to pull anything at all up to itself when it’s connected to a positive pressure plumbing system? If I pull the fuel line off the generator with the fuel pump operating, it’ll spray all over the roof, right?

So why is there any concern about the mechanical fuel pump in the generator lifting anything ?

Along the same lines of reason, how can an outboard steal fuel and suck air into the system from the generator fuel line when both are under positive pressure?

My brain says the only way that could ever happen is if the pump providing the positive pressure can’t keep up with the GPH of the system and the system pressure goes negative.

I’m lost. I can’t understand the dynamics of what you are suggesting can happen.

Where am I going wrong in my plumbing thinking? It all works like I picture for house and freshwater system in boats. Why not for fuel?

If the whole system is pressurized, your thinking is correct. I'd want a shutoff solenoid at each device though (or that device's line before it exits the explosives locker) to make sure you're not trying to push fuel to something that isn't running (just in case).

[Chotu]

Originally Posted by rslifkin

If the whole system is pressurized, your thinking is correct. I'd want a shutoff solenoid at each device though (or that device's line before it exits the explosives locker) to make sure you're not trying to push fuel to something that isn't running (just in case).

Ok!

This is the plan, then.

I’ll leave the system as is with the new proper high lift pump as linked to previously.

This will get the fuel to all the different devices.

I’ll add manual shutoffs that stay off unless you’re using a device. Then you’d turn them on. The added ball valves will be in the explosives locker with the tank selection manifold and everything else. All dangerous connections are located there.

Should work and be the most safe installation possible.

[Scubaseas]

Originally Posted by Chotu

Ok, this is where my thinking is breaking down. I think you found it.

I am picturing the whole thing like every other type of plumbing.

If you have a kitchen sink, a garden hose outside, a bathroom sink upstairs and a tub/shower upstairs in a house, one pump provides all the pressure to all the outlets and you can turn them on at the same time too.

Why doesn’t a fuel system work the same way as every other type of plumbing including boat freshwater plumbing??

Why does my generator need to pull anything at all up to itself when it’s connected to a positive pressure plumbing system? If I pull the fuel line off the generator with the fuel pump operating, it’ll spray all over the roof, right?

So why is there any concern about the mechanical fuel pump in the generator lifting anything ?

Along the same lines of reason, how can an outboard steal fuel and suck air into the system from the generator fuel line when both are under positive pressure?

My brain says the only way that could ever happen is if the pump providing the positive pressure can’t keep up with the GPH of the system and the system pressure goes negative.

I’m lost. I can’t understand the dynamics of what you are suggesting can happen.

Where am I going wrong in my plumbing thinking? It all works like I picture for house and freshwater system in boats. Why not for fuel?

You have it perfectly understood but you now have pressurized lines inside the boat and you violate ABYC standard 24.15.7 by having the pressure pump more than 12" from any engine.