Fuel pressure

Tony Davis · 09-01-2007, 09:40 AM

Just ordering some gauges, one of which is fuel pressure, anyone know what sort of psi a 2.5 offshore carb motor runs at? 0-15 psi be ok.

Matt · 09-01-2007, 09:57 AM

Reckon so.

Jon Fuller · 09-01-2007, 10:41 AM

less than 7 I think, so 15 is almost too much

Jon Fuller · 09-01-2007, 10:42 AM

probably 10psi would be ideal. best ask Neil Holmes

Matt · 09-01-2007, 10:54 AM

Pretty sure JBD made a post about it many moons ago.

Spanner Man · 09-01-2007, 01:41 PM

0 to 15psi gauge will be fine. OK if you are using a red holley pump but if using a blue holley need to set a regulator at 6psi or pressure will blow the float valves off there seats and flood the carbs.

JamesM · 09-01-2007, 08:41 PM

Quote:

Originally Posted by Matt

Pretty sure JBD made a post about it many moons ago.

Pretty sure I didn't!!!

I think carb motors run at around 5 PSI. And just for the record EFI's are 39 PSI (gold reg) or 56 PSI (black reg).

Matt · 09-01-2007, 08:44 PM

With hindsight, pretty sure you're right.

MrRob · 09-01-2007, 09:02 PM

Quote:

Originally Posted by Johnny Boat Dude

Pretty sure I didn't!!!

I think carb motors run at around 5 PSI. And just for the record EFI's are 39 PSI (gold reg) or 56 PSI (black reg).

Why is there such a big different in PSI between a carb and an efi?

scottyboy · 09-01-2007, 10:28 PM

Quote:

Originally Posted by MrRob

Why is there such a big different in PSI between a carb and an efi?

Because on a carb'd motor the engine draws the fuel in itself and all the pump has to do is keep the float chamber supplied with fuel.Any excess amount of pressure will stick the needle valv in the chamber open and flood the carb/carbs!
With an efi the fuel is injected in by the electronic injector therefore has to be under pressure at the fuel rail hence electronic fuel injection!

Matt · 09-01-2007, 10:36 PM

You "could" have a carbed motor run 40+PSI, if you could get the float valves to seal!