US1 Fountain

iTrader: (1)

Do the mechanical stock pumps always pump same pressure, or does it increase with rpm?

How much pressure can a Q-jet take before it unseats?

Thanks


added:

Is it possible for a stock Merc high volume pump to put out 20psi at 2000rpm? Curious if a buddy was sold the wrong pump.

BAD ASS SCARAB

Stock pump about 5 to 6.5 lbs depending on the RPM . Anything over that your asking for problems. Damaged needle and seat bent float arms from fuel comming past the seat. If your going to run a high volume pump put in a fuel regulator and set it about 5 to 6 lbs.

Boat1

The pump volume increases with rpm but the presure should not exceed 7 psi on a stock mechanical fuel pump. Sounds like the pump is wrong or defective.

US1 Fountain

iTrader: (1)

Ok, thanks guys.

This is a buddies boat been working on last couple weekends. stock '88 454. Dumps fuel past N/S. tried new kit, float and carb body, no change, thus eliminated carb as the culprit. He just put a press gauge on it today.

MILD THUNDER

iTrader: (3)

I get 8psi at idle. 1050 Dominator, holley 120GPH six valve marine pump. High flow needle and seats, no problems.

However, you are working with a different animal. Sounds like he may be needing a pump.

US1 Fountain

iTrader: (1)

I agree now that we know what the pressure actually is. I didn't think the mechanical pump was capable of that high of a pressure, so it never entered my mind as the problem.
A new pump is on it's way now.

BAD ASS SCARAB

US1 The slinkie joke is some Funny s##t thanks!

US1 Fountain

iTrader: (1)

...

morrowcarl72

what kind of volume and or pressure will a factory mechanical pump from a 502mag off the water pump give???

will it support a 502 carb motor with a 800cfm holley without the electric pump that is high pressure for the efi

Mbam

Some of the OEM Merc pumps are doing just that - too much pressure. We have warrantied a bunch.