carb psi

**daytrader** · 06-25-2018, 10:42 AM

Whats the average fuel psi for a 200 merc carb motor? thankx, Gary

**eli** · 06-25-2018, 10:57 AM

3 to 4 psi for diaphram pump

**VooDooChild 1267** · 06-25-2018, 11:51 AM

I run an electric pump and try to keep it under 4,which can be tricky.Anything over 5 and it can unseat the needles and flow out the carb.I just picked up a bypass regulator to take the pressure off the pump to keep it cool and keep it at 3 1/2 lbs,just have not had the time to install it yet.

**daytrader** · 06-25-2018, 12:04 PM

I just installed a small electric pump, it varies 4 to 6 psi, havent run it yet, but it really has good flow. I do have a regulator, think Ill set it at 3.5, see what happens. Thankx for the info.

**Forkin' Crazy** · 06-25-2018, 01:27 PM

Originally Posted by VooDooChild 1267

I run an electric pump and try to keep it under 4,which can be tricky.Anything over 5 and it can unseat the needles and flow out the carb.I just picked up a bypass regulator to take the pressure off the pump to keep it cool and keep it at 3 1/2 lbs,just have not had the time to install it yet.

You will like it!!! I love mine!

**mach351** · 06-25-2018, 04:35 PM

New needles and seats should be able to allow at least 5psi. I’d run as much as you can.

**dwilfong** · 06-25-2018, 06:33 PM

I drilled my seats and run 7 1/2 psi..........................kinda over kill but I sleep good at night........LOL

**eli** · 06-26-2018, 01:57 PM

what drill ?

**dwilfong** · 06-26-2018, 03:39 PM

To tell you the truth I do not remember what size. I checked the tip of the needle and made sure it was not bigger than the Viton tip.

**FMP** · 06-26-2018, 04:40 PM

You drilling cause your bowls are running low on fuel, higher fill rate?

**dwilfong** · 06-26-2018, 06:06 PM

Originally Posted by FMP

You drilling cause your bowls are running low on fuel, higher fill rate?

I am using the two bowl WH carbs right now.
Just covering all bases after a few melt downs.
Knock on wood all good so far.......................

**FORBESAUTO** · 06-26-2018, 06:55 PM

I done the same thing on a set of wh20’s I’m running now on new mota , don’t remember what size I drilled em either. I also removed a lot of material in bowl below the center pedestal to increase the bowl volume. I have yet leaned the idle circuit out enough yet for a good clean idle and good response. I’m assuming it’s because of the extra weight of the added fuel richining it up, kinda like raising float level without raising it? Seems to be able to hold a little pressure also over the stock size holes? My regulator started acting stupid and can’t get it above 5 psi, but holds that fine with no leaking. On stock setups I usually ran em around 4, because around the 5 psi mark was asking for trouble, it was shoot match if they where gonna hold or not. I guess each set of carbs are different.

**dwilfong** · 06-26-2018, 07:18 PM

Originally Posted by FORBESAUTO

I done the same thing on a set of wh20’s I’m running now on new mota , don’t remember what size I drilled em either. I also removed a lot of material in bowl below the center pedestal to increase the bowl volume. I have yet leaned the idle circuit out enough yet for a good clean idle and good response. I’m assuming it’s because of the extra weight of the added fuel richining it up, kinda like raising float level without raising it? Seems to be able to hold a little pressure also over the stock size holes? My regulator started acting stupid and can’t get it above 5 psi, but holds that fine with no leaking. On stock setups I usually ran em around 4, because around the 5 psi mark was asking for trouble, it was shoot match if they where gonna hold or not. I guess each set of carbs are different.

I had a cheep Mr Gasket bypass regulator on it at first and a Carter marine pump. Both where a joke.......
When to the local speed shop and got a 15 psi 135 GPH pump that the owner recommended that all the guys use and have no problems with. $100 china no name special...LOL
Well the cheep regulator took a dump real quick with that pump.
Got a Holly bypass regulator and all good. was preset at 7 1/2" PSI out of the box. Got a LARGE gauge and mounted it up front to keep a eye on this ****.
Hold 7 1/2" all the time no fluctuation at all.
You can see the fuel returning in to the clear tanks like a fire hose.
No problem with the seats holding the pressure.
Took the 3 hole on the top throttle plates out of the WH-15 and put a set in with two holes. Changed the idle dramatically. Turned the timing up and all is good now.
3 holes let to much air in and had to turn the timing down all the way to get it to 1500.
2 holes is just right got the timing back up and the bottom end response is great now.