Rebuilt Carb. Having problems. PLEASE HELP

[AaronWhitt82]

Hey guys whats up? Just joined the forum and I'm looking for some help.
I have a '99 Moomba Outback with the Indmar 350 and Holley 4150 Carb.
I just recently rebuilt the carb myself, but am still having problems with how the motor is running.
I also have recently replaced: Fuel pump, fuel filter, spark plugs, cap, rotor, & impeller.

So here is the issue:
The Boat would start up and idle no problem and seemed to be running perfect.
Well after 3 minutes or so at idle it would start running rough and bog down and then eventually die out so I started it back up again and no problem; idled fine and ran smooth.
After it was running a few minutes I revved her up a bit in neutral and same thing; it started bogging down so I pumped the throttle a bunch and then it sounded like she was going to come out of it for a second, but then it died on me. Seems like she isn't getting enough fuel/runs out of fuel for some reason and then it dies out.
I took the sight plugs out to see where the float levels were and they were set just right to where there was barely some fuel trickling out of them. I let the boat run and kept and eye on the sight plugs:
The secondary level stayed the same and I could see the fuel level right at the sight plug. On the primary, the float would drop way down and I wouldn't be able to see the fuel anymore. I then shut the boat off and turned the key to run to where it would fill back up with fuel to the sight hole again. Then I started it at idle and the same thing.... Secondary level would stay the same and primary would go way down. Also the primary float is Brass and the Secondary is Nitrophyl if that makes a difference.
Question: Is that the correct way they are supposed to work? or is there something incorrect to where maybe the primary isn't getting enough fuel and causing it to die after a few minutes?
If this isn't the problem then I'm not sure what else to check.
I've checked everything the Holley Tech manual said to for troubleshooting, but none of that seems to be the problem.
Thanks in Advance,
Aaron

 

[Waffle]

Re: Rebuilt Carb. Having problems. PLEASE HELP

Fuel tank vent?

 

[Benny1963]

Re: Rebuilt Carb. Having problems. PLEASE HELP

recheck pumpdiafram and primary needle and seat and also fuel pressure
at carb anti syph valve if you have one. and venting your primary should stay full with correct fuel pressure also may be bad float
b1963

 

[Maclin]

Re: Rebuilt Carb. Having problems. PLEASE HELP

The power valve diaphragm may be ruptured, can happen with a backfire. That would drain the primary bowl and not the secondary bowl.

 

[Reel Poor]

Re: Rebuilt Carb. Having problems. PLEASE HELP

First.....If your fuel pump continuously runs with the key in the on position (engine off) it's not properly wired.

Second.....Is the pump running when the engine is running? If so check the fuel pressure, 5 to 7 lbs should be good.

Here is another test you can do. Testing Your Boats Fuel System

 

[AaronWhitt82]

Re: Rebuilt Carb. Having problems. PLEASE HELP

Hey, Thanks! I appreciate the replys

I guess I need to check a few things on the fuel tank then to make sure it is operating correctly.

I know it has an anti-siphon valve on the tank because I have checked it before and it seemed to be operating correctly. Maybe I will buy a new one just to be safe.

Also, how do I check to make sure the fuel tank vent is working correctly? Can I disconnect it and blow some compressed air through it?

Maybe it is vapor locked?

I have also checked the fuel pickup tube and screen and it was clear of debris.

I will also double check the pump diaphragm and needle and seat, but considering they are brand new I don't know if that would be the issue.

The power valve is brand new as well and it hasn't backfired since the new one has been installed so I think I could eliminate that.

Also since I installed the new fuel pump, it DOES run with the key on and motor not running. I will check to make sure it is wired correctly and I need to check that it is runnning constantly while the motor is running.

If it's not then maybe I need to replace the fuel pump/oil pressure safety switch thingy.

Thanks again guys!
Aaron

 

[Benny1963]

Re: Rebuilt Carb. Having problems. PLEASE HELP

hi put fuel pressure gauge on line check running 5to7 psi
check flot levels again they should adjust external put vacum gauge on entake match power valve to manifold vacum and check all other answers on post about fuel del some new 4150 come with blow proof power valve
protection .
repost if you have probs with carb ,i have been building holleys for
my motorsfor along time they are good carb
so it may not be youre carb ,
b1963

 

[AaronWhitt82]

Re: Rebuilt Carb. Having problems. PLEASE HELP

Thanks for the reply Benny.
I wish I had access to a vacuum and fuel pressure gauge, but I don't. I might be able to ask around and find someone that has them.

I'm thinking about getting a 5 gallon gas can and hooking up a fuel line to the pump and see what happens with that.

The carb on my boat is older and doesn't have the power valve blow off protector on it.

I also called Holley a few days ago and spoke to a tech guy. I asked him the specs for my carb. P/N 75021-1 and he said 2.5 power valve, 70, primaries and 76 secondaries for the jets and thats exactly what is in the carb.

I'm still wondering about the fuel pump though and why it is running with the key on and motor not running. I thought I had it hooked up wrong, but I don't. I still need to check and see if the pump is running while the motor is and put a test light on some wires.
Maybe there is a wiring issue and it is getting power cut to the pump while the boat is running?

I'm going to disconnect the line to the fuel pump and blow compressed air through it all the way back through the fuel tank and see if that does anything.
I'll keep updating as I check and test everything.....
Thanks again!

 

[Benny1963]

Re: Rebuilt Carb. Having problems. PLEASE HELP

hey if you have to put self regulating pump 5to7 psi to key only hot
and you wont have to worry about that there cheap
2.5 inch power valve is way low a 6.5 is usually a good starting point
on a carb 350 if you have a 2,5 valve your idle circ is opening way to soon
you usually see something that low on a race car that doesnt idle long
and some people take them out on race cars and block them
because race motors dont build much manifold vacum.
did you buy carb new it seems like alot of carb for small block
repost if i can help
benny1963

 

[AaronWhitt82]

Re: Rebuilt Carb. Having problems. PLEASE HELP

hey if you have to put self regulating pump 5to7 psi to key only hot
and you wont have to worry about that there cheap
2.5 inch power valve is way low a 6.5 is usually a good starting point
on a carb 350 if you have a 2,5 valve your idle circ is opening way to soon
you usually see something that low on a race car that doesnt idle long
and some people take them out on race cars and block them
because race motors dont build much manifold vacum.
did you buy carb new it seems like alot of carb for small block
repost if i can help
benny1963

Hey Benny, the Airtex fuel pump I have installed has a max of 7 PSI. I cross referenced it from the stock Carter one. I found out today that it isn't Marine approved like the parts guy said it was so I need to get a different one. Hopefully they take it back and exchange it for me once I show them on the directions where it says NOT FOR MARINE OR AIRCRAFT USE!

The rebuild kit I bought came with the 6.5 power valve, but like I said the one I pulled out of the carb was a 2.5 so thats what I replaced it with.
You think I should go ahead and switch it to the 6.5 and see what happens?
How will the boat run different by changing from the 2.5 to the 6.5?

This is also the stock carb that the boat came with and it is alot of carb for the motor size.....

Thanks

 

[Benny1963]

Re: Rebuilt Carb. Having problems. PLEASE HELP

yes if it has a 2.5 power valve its opening at very low vacum level
if your running a fairly stock cam you should have a lot more vacum than that
the 4150 i have run on 383 strokers making 475 to550 hp
the jet size is also quite steep
i dont know how well it ran on that carb but it should load up at idle
with that primary setup and power valve
you might try to find some one that would swap or let you run there carb for a few miles 600 to725 cfm i run a 750 jetted to 68 primary 6.5 power valve
with 7lbs vac on a 30 over 350 flat top pistoned motor comp cams hyd
split duration 500 510 at 50 with 882 stock cyl heads with good springs
it makes 345 hp in my work truck everyday
so hang in there you will get it keep posting illwatch
b1963

 

[Benny1963]

Re: Rebuilt Carb. Having problems. PLEASE HELP

oh by the way let it run till it dies out .then check spark plugs close to the center uof the intake and see if they are gas fouled they load up first

 

[Maclin]

Re: Rebuilt Carb. Having problems. PLEASE HELP

Use the 2.5 powervalve. This is a boat not a car. Boat engines are always under load, the vacuum "curve" is not the same as a car. The 2.5 is correct, the boat engine builders know what they are doing regarding using a 4150 Holley for their boat engines.

 

[AaronWhitt82]

Re: Rebuilt Carb. Having problems. PLEASE HELP

OK guys.... Like I said when I called Holley tech support the guy said to stick with the 2.5 power valve, 70 primaries and 76 secondaries.
I am also at sea level. He said if I was above sea level then I might want to go to a bigger power valve and change jet sizes.
So now your staying to stick with the setup I have;
Correct?

It ran fine before the rebuild with that setup and then...
Under full throttle after maybe 20 seconds the motor would bog down and lose power, but would not die out.
When it would bog I would pump the throttle a bunch and it would hesitate like it would come out of it, but it didn't and would come back to an idle.
It also seemed to run fine under 3,000 R's, but once in a while would bog down. Only seemed that over 3,000 it was the worst.
Thats why I chose to rebuild the carb. and am still having some sort of fuel issues with the boat only running a few minutes then dying out like shes starving for fuel..... But after it dies she starts right back up.

I'm also thinking once I get this damn oil pressure switch/fuel pump issue figured out then I can go from there with the carb to see how it runs...

Just some history: The previous owner only used the boat maybe once or twice a year, but had it serviced in spring and winter at the local marina. Not sure if this had anything to do with why it eventually started to run improperly.....

 

[Maclin]

Re: Rebuilt Carb. Having problems. PLEASE HELP

"....I'm also thinking once I get this damn oil pressure switch/fuel pump issue figured out then I can go from there with the carb to see how it runs..."

You are on the right track.....the carb tuning setup certainly would not cause the problems you describe. In fact you stated that the same symptoms were around before that rebuild, so I am on the side of the carb rebuild and tuning setup NOT being a factor now.

No real effort wasted as carbs can always use a freshening but the real problem is still there and is in the fuel delivery system somewhere before the carb. Several areas to check involving electrical components (pumps and switches), plumbing (filters, tubing/hoses, fuel tank pickup), and wiring (bad grounds or connections, shorts, corrosion).

Running from a separate fuel tank would show if it is a tank pickup or venting issue.

Relax a little and hang with it....You have the right mindset now and I am positive you will ferret it out soon.

 

[AaronWhitt82]

Re: Rebuilt Carb. Having problems. PLEASE HELP

Yea I tore apart the whole fuel system yesterday and checked everything I could in it!

Anti-siphon valve is out and being replaced today
Tank vent seems fine
Pickup tube has been checked and no cracks or leaks in that
Pickup screen at bottom of tank is clear of debris
Checked fuel line from tank all the way to fuel filter and to the fuel pump. No leaks or kinks.
The filters in the fuel lines at the carb have been cleaned during the rebuild
Also need to switch my fuel pump out with the correct marine approved one

So now like I said all there is to figure out is the oil pressure switch and some wiring and I'll go from there....

 

[AaronWhitt82]

Re: Rebuilt Carb. Having problems. PLEASE HELP

Alright guys I replaced the anti-siphon valve and hooked all fuel lines back up and put a new fuel filter on.
I disconnected the line that screws into the dual line at the carb.
I turned the key on and let fuel pump run (I'm waiting on a new oil pressure switch) and it ran a few seconds, but no fuel would come out of the line. I then cranked the motor over a few times and no fuel coming out.
I then turned the key on and off a bunch but no fuel.
I'm thinking the line needed to be primed somehow so I disconnected the fuel line at the anti-siphon valve and poured gas down the fuel line until it was full.
Went back and cranked a bunch and still no fuel

Can someone point me in the right direction to figure out how to get the pump to draw fuel from the tank and through the AS valve?
Thanks

 

[Benny1963]

Re: Rebuilt Carb. Having problems. PLEASE HELP

sorry about bad info im a car guy have built buches of holleys
i assumed that at idle in neutral that the motor would make more than 4lbs of vacume and since the power valve is only to idle and transition
into higher rpm and is then usless dont know much about inboard boats
and i am learning from these post
have several outboards which are a pain in the butt,
because power heads cost as much as a 350
watched nova 19 video and have started looking
thanks yall
b1963

 

[Reel Poor]

Re: Rebuilt Carb. Having problems. PLEASE HELP

For about 25 dollars or less you can buy a combination vaccum/fuel pressure tester from a local discount auto parts store and do the test I posted earlier.

Looks like this.

 

[MikDee]

Re: Rebuilt Carb. Having problems. PLEASE HELP

Alright guys I replaced the anti-siphon valve and hooked all fuel lines back up and put a new fuel filter on.
I disconnected the line that screws into the dual line at the carb.
I turned the key on and let fuel pump run (I'm waiting on a new oil pressure switch) and it ran a few seconds, but no fuel would come out of the line. I then cranked the motor over a few times and no fuel coming out.
I then turned the key on and off a bunch but no fuel.
I'm thinking the line needed to be primed somehow so I disconnected the fuel line at the anti-siphon valve and poured gas down the fuel line until it was full.
Went back and cranked a bunch and still no fuel

Can someone point me in the right direction to figure out how to get the pump to draw fuel from the tank and through the AS valve?
Thanks

Is your tank vent clogged? the only thing I can come up with? maybe the vent line is kinked? anyway, can you remove the vent line at the tank, and temporarily leave it open to the atmosphere, or put a length of open hose on it, to take it out of your way, and then try it again.