What should a C40TLRX fuel pump pressure be?

[99yam40]

I was going to buy a Vac/ Pressure gauge to test the fuel system today but did not know what the pressure is suppose to be. I found something that said the Vac should be 0-5 "Hg
I tried to find it in the manual and did a search in the forum but did not see any pressures listed. Will a gauge that goes up to 10 PSI do the trick?
What pressure should I see at idle and WOT?

 

[99yam40]

Re: What should a C40TLRX fuel pump pressure be?

I ran the motor on the muffs and the pressure coming off of the fuel pump was at 2.5 psi at idle and fast idle. It fell to 0 when I pinched off the incoming fuel line and did not have any bubbles coming though of the clear line I had tied in coming out of the pump so it does not have any air leaks. I will put it in the water to make sure about under load soon.

When I attached the gauge in the suction side of the pump it shows 1" of vacuum and when I pinch off the line coming up to the motor it drops to 6" of vac. so the fuel system seems to be ok but I do not know where the pressures should be

Can someone tell me if 2.5 psi is a good fuel pressure for this 1999 carbureted 40 hp motor?

 

[rodbolt]

Re: What should a C40TLRX fuel pump pressure be?

2.5 is marginal but may work.
what we are looking for is pressure, and vacum at the pump outlet,pressure,and inlet,vacum, while the beast is at the problem RPM AND its full load, not on a flusher.
max intake vacume is 4"Hg at 5000 RPM while under its normal load.

 

[99yam40]

Re: What should a C40TLRX fuel pump pressure be?

Checked the pressure at WOT today and it was at 5 PSI and i did not have any bubbles through the clear tubing I had run to the carbs from the pump for testing. I have read that the pressure should be 5-7 psi on carbed motors is this correct for Yamaha's?