Fuel pump recommendation...

[brendellajet]

Happy Father's Day to all the Dad's on here.
I'm looking for a recommendation for an electric fuel pump. Motor is a Chevrolet 540 making 800 up @6100. I currently have a Clay Smith Mechanical pump on the motor but I need the fuel pump drive for my raw water pump.

I guess I could go with one of the mercruiser style mechanicals that mount to the water pump as well, but was kind of looking to get away from the pumping delay that occurs when the boat has been sitting a while. This is a new to me install and the fuel tank IS really close to the motor so total distance of fuel li e from tank to pump is 5 ft or so, not sure how that changes things if at all if I were to stay mechanical.

Any recommendations? Not afraid to spend some coin, just looking for something that has a good track record/reliability and ideally that is also rebuildable.

Thanks all!

 

[Racey]

These are meant to be pretty good:

https://www.circletracksupply.com/cv-spin-mp-2551-fuel-pump-11.5-psi-120-gph.html

What kind of raw water pump runs off the block fuel pump drive?

 

[Riverbottom]

Tough call, pretty hard to beat a Clay Smith mechanical pump.

 

[brendellajet]

These are meant to be pretty good:

https://www.circletracksupply.com/cv-spin-mp-2551-fuel-pump-11.5-psi-120-gph.html

What kind of raw water pump runs off the block fuel pump drive?

Came from mercruiser 502 mpi. Now that I think about it, it just occupies the same space. It's belt driven...my bad.

 

[Racey]

Came from mercruiser 502 mpi. Now that I think about it, it just occupies the same space. It's belt driven...my bad.

Is your block a Mark IV with the fuel pump provision? if so i would run the fuel pump there.

 

[brendellajet]

It's a Merlin block with the provision, but the water pump is going to be in the way of the fuel pump. I'll try to get some pics when I bring the boat home next week.

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[Racey]

It's a Merlin block with the provision, but the water pump is going to be in the way of the fuel pump. I'll try to get some pics when I bring the boat home next week.

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Have you considered switching to a jabsco style water pump bracket that gets the pump lower than the fuel pump?

I would retain the cam/pushrod pump rather than go to an electric or waterpump driven fuel pump

 

[brendellajet]

Have you considered switching to a jabsco style water pump bracket that gets the pump lower than the fuel pump?

I would retain the cam/pushrod pump rather than go to an electric or waterpump driven fuel pump

I haven't, bit appreciate the suggestion. I'll check it out. Sounds like it could save me some coin. Thanks!

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[Husqy510]

Problem with electric fuel pumps is they often loose the prime if the pick up goes dry, and they fail more often than mechanical pumps

 

[rrrr]

The "delay" of a mechanical fuel pump's output when starting the engine lasts a couple of seconds at most. A healthy starter and battery will spin the engine about 200 RPM, or more than 3 times a second. A cam driven pump operates every other engine revolution, and a belt driven pump is stroked about the same rate.

One pump cycle easily produces enough volume to pressurize the fuel line to the desired 7-9 PSI. That volume is also greater than the amount of fuel expended by the accelerator pump of two carburetors. By the time you count 1,001 and 1,002, the pump has stroked at least twice.

The reliability of a mechanical pump far exceeds that of an electric pump, and it will easily produce enough fuel to feed a 800 HP engine with two carbs running at 7,000 RPM.

 

[brendellajet]

The "delay" of a mechanical fuel pump's output when starting the engine lasts a couple of seconds at most. A healthy starter and battery will spin the engine about 200 RPM, or more than 3 times a second. A cam driven pump operates every other engine revolution, and a belt driven pump is stroked about the same rate.

One pump cycle easily produces enough volume to pressurize the fuel line to the desired 7-9 PSI. That volume is also greater than the amount of fuel expended by the accelerator pump of two carburetors. By the time you count 1,001 and 1,002, the pump has stroked at least twice.

The reliability of a mechanical pump far exceeds that of an electric pump, and it will easily produce enough fuel to feed a 800 HP engine with two carbs running at 7,000 RPM.

Simply not the case on my setup. In the past I have cranked for up to 30 seconds for first trip of the year. Guessing it is taking longer to pump through the water/fuel separator...don't know what else it could be.

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[rrrr]

Simply not the case on my setup. In the past I have cranked for up to 30 seconds for first trip of the year. Guessing it is taking longer to pump through the water/fuel separator...don't know what else it could be.

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Crank the engine for a four count when it's cold. Look into the carbs and pump the linkage a full stroke. There should be enough pressure built in that short amount of time to feed the accelerator pumps for one and maybe two shots.

The first trip of the year means the carb bowls and accelerator pump reservoirs are empty, and there's no residual fuel in the manifold and cylinders. The needle valves have opened when the fuel in the carbs evaporated, and the fuel in the line between the pump and carbs has also evaporated. Thirty seconds isn't excessive under those circumstances. The same issues are present after a week, but since the time period is shorter there's more residual fuel in the line and less cranking time is required.

How much initial timing are you running? More than 8-10 degrees will affect the cold starting ability of the engine.

 

[Racey]

Crank the engine for a two count when it's cold. Look into the carbs and pump the linkage a full stroke. There should be enough pressure built in that short amount of time to feed the accelerator pumps for one and maybe two shots.

The first trip of the year means the accelerator pump reservoirs are empty, and there's no residual fuel in the manifold and cylinders. The needle valves have opened when the reservoirs empty, so the fuel in the line between the pump and carbs has evaporated. Thirty seconds isn't excessive under those circumstances. The same issues are present after a week, but since the time period is shorter there's more residual fuel in the line and less cranking time is required.

How much initial timing are you running? More than 8-10 degrees will affect the cold starting ability of the engine.

Yep exactly this right here, even if you have an electric pump you still have to squirt the accelerator pumps a couple times after the carb has been dry just to get them to prime past their check valves and then fill the accelerator pump exit ports.

If you want to wait all winter and have the boat fire on the first shot you better start saving your nickels for EFI.

There is nothing wrong with cranking for 15-30 seconds at the beginning of the season anyway to get the oil pump moving fluid before the engine lights.

Do exactly what rrrr says, Crank the engine for maybe 4-5 seconds, cycle the throttle 3 full pumps, then crank again.

If you have the engine hatch up (as you should) you can hear the accelerator pumps squirting fuel. If you go back and squirt them manually you can feel it when they prime up and get resistance from the gasoline and begin pumping liquid.

The First pump will be dry and upon you closing the throttle from full to idle the accelerator pump will then fill with fuel as the diaphragm expands, accelerator pump will be about 50/50 air and fuel at this point, second pump clears the rest of the air out and squirts some fuel, 3rd pump should be full blown fuel.