What fuel pump??

[Chotu]

Originally Posted by Cheechako

It is interesting... so your typical small boat or even dingy with an outboard has no external lift pump, I assume they have internal pump of some sort...

The big ones we worked on with say 250HP outboards had the tank in the V hull so maybe 3 ft below the engine head...
Once started you would think fuel would siphon with no pump...?

Are you sure you dont have another issue going on making fuel hard to lift and destroying pumps in a situation where you dont really even need a pump? Are the engines competing with each other from the same line?

The engines definitely have their own pumps. But it’s not enough I guess. It doesn’t work.

I run one engine at a time. And they sip fuel anyway. 30 hp. Not much different than a dinghy motor.

[Chotu]

Originally Posted by rslifkin

That would be a tough one to solve, I think. Only thing I can think is a bulkhead connector in the bulkhead and fuel hose connected to it on either side. More watertight, but it adds additional connection points compared to a contiguous hose.

Yeah, but everything’s already installed. The boat has 1000 miles on it under motors already.

I just keep losing fuel pumps. At what I consider an unacceptable rate.

[Chotu]

Originally Posted by rslifkin

That's a good point. If it's all manifolded off 1 tank pickup, that may be a problem. Many engines spec that they need their own dedicated pickup.

These are 30 hp outboards. At wide open throttle they are 3 gallons per hour.

I could keep up with them with a straw. Lol sucking with my own mouth.

These tanks are designed for big boats with
big engines. The pick up is like half an inch. Fuel lines are all oversized at 3/8 of an inch.

I’ve also never had any problem when I did run both motors and a generator at the same time. Everything is way oversized for the fuel I need. I’m just having pump failures.

[rslifkin]

Originally Posted by Chotu

These are 30 hp outboards. At wide open throttle they are 3 gallons per hour.

I could keep up with them with a straw. Lol sucking with my own mouth.

These tanks are designed for big boats with
big engines. The pick up is like half an inch. Fuel lines are all oversized at 3/8 of an inch.

I’ve also never had any problem when I did run both motors and a generator at the same time. Everything is way oversized for the fuel I need. I’m just having pump failures.

That certainly shouldn't be a bottleneck anywhere then. 3/8" fuel lines feed my engines just fine and they're a whole lot bigger.

[Sorry AboatThat]

Hi,

Sorry if I missed it somewhere in the thread... I have not read any concern having the filter on the inlet side of the pump. Unless it is anything other then a strainer it could be causing the pump to work harder then designed. Any pumping application I have used/designed have had any fine filtration on the pressure side of the pump.

good luck

[Chotu]

Originally Posted by Sorry AboatThat

Hi,

Sorry if I missed it somewhere in the thread... I have not read any concern having the filter on the inlet side of the pump. Unless it is anything other then a strainer it could be causing the pump to work harder then designed. Any pumping application I have used/designed have had any fine filtration on the pressure side of the pump.

good luck

OK! Maybe that is the error of my ways. It was suggested elsewhere in the thread that I changed the order also.

For some reason, I was thinking that you didn’t want pressure in a filter.

It’s a standard Racor filter and water separator.

I’ll get the same pump and change the order so the filter is after the pump.

[rslifkin]

Originally Posted by Chotu

OK! Maybe that is the error of my ways. It was suggested elsewhere in the thread that I changed the order also.

For some reason, I was thinking that you didn’t want pressure in a filter.

It’s a standard Racor filter and water separator.

I’ll get the same pump and change the order so the filter is after the pump.

Most marine filters are installed as draw through, but that's partly because of on-engine pumps being after the filter by nature. But as long as the pump will only output low pressure, putting the filter after the pump is ok. The standard gasoline Racors are rated for 7 psi from what I can find, so in a low pressure lift pump or carb scenario, they're fine to use after the pump. Just not at fuel injection pressures. Racor does make an oddball cartridge filter unit (model 110A) that they show as good for 100 psi.

There's definitely a good chance that those lift pumps push better than they pull through resistance, so putting the filter after the pump may improve things.


Just make sure you check output pressure of the pump before switching. There's a chance you'll need a lower pressure pump or a pressure regulator setup. But that's not a bad idea to pay attention to anyway (to minimize pressure in the fuel manifold, etc. for minimum leak risk).

[Cheechako]

Originally Posted by Sorry AboatThat

Hi,

Sorry if I missed it somewhere in the thread... I have not read any concern having the filter on the inlet side of the pump. Unless it is anything other then a strainer it could be causing the pump to work harder then designed. Any pumping application I have used/designed have had any fine filtration on the pressure side of the pump.

good luck

Most boats have the Racor or similar filters (other than the engine factory filter) on the suction side between the tank and engine.

It IS better in general to let a pump push through a filter though IME.

[Sorry AboatThat]

Reminder: Pumps don't suck, they create vacuum that allow atmospheric pressure to push the liquid in to the pump. The pump then creates flow, and responds to restrictions on the pressure side that increase pressure.

[nofacey]

Install 2 of the pump that ran the longest so you have an installed spare.
- if you move the Racor, you’ll need to add a screen ahead of the fuel pump….these types usually come with a small inline filter to protect the pump.

Might want to doublecheck your fuel lines for vacuum leaks…..once primed, the out board lift pumps should do the job…..if not, you’re pulling air in somewhere.

Usually easiest done by pulling the connection furtherest back, plugging, and testing using air pressure & sopy water. I’d take a good look at your manifold.

[Chotu]

Originally Posted by nofacey

Install 2 of the pump that ran the longest so you have an installed spare.
- if you move the Racor, you’ll need to add a screen ahead of the fuel pump….these types usually come with a small inline filter to protect the pump.

Might want to doublecheck your fuel lines for vacuum leaks…..once primed, the out board lift pumps should do the job…..if not, you’re pulling air in somewhere.

Usually easiest done by pulling the connection furtherest back, plugging, and testing using air pressure & sopy water. I’d take a good look at your manifold.

Actually, maybe I don’t need to use the Racor at all. I think it was overkill. I just got a little paranoid about fuel quality.

The very first time I filled this boat up, they gave me a tank of water and it destroyed my fuel injectors. In both engines. Everything was brand new.

But anyway, this is what the pumps look like. They have their own built-in screen and fuel water separator. Good enough right? I have to say, I haven’t seen a bit of anything on the Racor. Since this is gasoline, there’s nothing. It’s not like there’s a bunch of fuel scum like diesel tanks get.



I do like the idea of having a secondary back up pump plumbed in and ready to go. I will definitely do that. That will avoid the case where the engines die at a bridge or something.

Maybe I can transfer the Racor to the dinghy. It’s the small gasoline model anyway.

[rslifkin]

Originally Posted by Chotu

Actually, maybe I don’t need to use the Racor at all. I think it was overkill. I just got a little paranoid about fuel quality.

The very first time I filled this boat up, they gave me a tank of water and it destroyed my fuel injectors. In both engines. Everything was brand new.

But anyway, this is what the pumps look like. They have their own built-in screen. Good enough right? I have to say, I haven’t seen a bit of anything on the records. Since this is gasoline, there’s nothing. It’s not like there’s a bunch of fuel scum like diesel tanks get.

Do your engines and generators have onboard filters? If so, you can probably get away without the Racor. As long as you keep the tanks dry, gas usually stays pretty clean. I dump the spin-ons on my engines (the only filters in the line) into a container when I change them to see what comes out. It's usually just a couple of little specks. I've never cut one open to see what may be stuck in the filter media, however.



I do make a habit when using non-ethanol gas of throwing some Iso-heet in the tanks every time I add gas (I usually throw 2 bottles in each tank, nowhere near the recommended bottle per 20 gallons). I figure that should soak up any tiny bits of moisture that find their way in so they don't accumulate at the bottom and corrode my aluminum tanks (or cause an issue when I go somewhere that I end up filling up with E10 gas).

[Bill Seal]

Look into a Carter rotary vane pump. Basically what's in the fuel tank of almost all cars, but lower pressure

[sailormed]

“Though electrical components (such as a fuel pump) can spark and ignite fuel vapors, liquid fuel will not explode (see flammability limit) and therefore submerging the pump in the tank is one of the safest places to put it.”

Why reinvent the wheel when millions of cars drive with fuel pumps immersed in the petrol tank?

[rslifkin]

Originally Posted by sailormed

“Though electrical components (such as a fuel pump) can spark and ignite fuel vapors, liquid fuel will not explode (see flammability limit) and therefore submerging the pump in the tank is one of the safest places to put it.”

Why reinvent the wheel when millions of cars drive with fuel pumps immersed in the petrol tank?

There are a couple reasons to avoid it here. Then you need 1 pump per tank (select between them when switching the valves). And you have more pressurized gas lines, which means more risk of something going very wrong.