Carb problem or water in gas?

[AaronWhitt82]

Indmar Chevy 5.7L 310HP with Holley 4150 carb. PN 75021-1 ***(originally thought it was a 4160) ***
Problem just started last week. I rebuilt the carb 2 Summer's ago.
Boat will run fine while idling, but when launching the boat or after getting up on plane or pulling a skier it bogs almost like it is running out of fuel and then if I pump the hell out of the throttle it will come out if it and sometimes it will backfire and then run normal.
It only does it periodically, but every time when I launch now after I start it up to get her warm she will run a few minutes, bog, then die out. I then pump the throttle a bunch and crank and crank and crank and then finally it will start back up and run fine.
Other times when it's been on plane it has bogged and died totally. Sometimes it takes a while to get it started back up and other times it starts no problem and runs fine.
I've checked the choke plate and when the boat is warm it is fully open.
I've checked the float levels and they are fine.
Just replaced the water/fuel seperator
I've also opened the gas cap thinking it might have been vapor locked, but I doubt it is that.
I turned the air/idle mixture screws all the way in and the boat dies so it's not the power valve.
Also when I hammer the throttle from idle it jumps right up and takes off so I'm leaning away from the acc. pump diaphram.

I'm thinking it has water in the tank and when the boat is at an angle (on plane or on the launch ramp) than it might be sucking water up from the bottom.
If it isn't this then I'm not sure what else it could be in the carb?

Thanks in advance

 

[Bondo]

Re: Carb problem or water in gas?

I'm thinking it has water in the tank and when the boat is at an angle (on plane or on the launch ramp) than it might be sucking water up from the bottom.

Ayuh,... You just changed the fuel filter,... How much Water was in it,..??

 

[ENSIGN]

Re: Carb problem or water in gas?

empty the filter into a glass jar,let it settle out and look for a separation of fuel and water.

 

[Maclin]

Re: Carb problem or water in gas?

The accel pump gets fuel from the very bottom of the bowl where water would be, so it is odd that the accel pump gets good enough fuel to richen it up and go if there is a water problem. Let us know what the filter contents look like.

It just sounds like a main jet circuit problem to me, or a fuel bowl level/fuel delivery issue at the needle/seat maybe. Easy enough to check the bowl level if it has sight plugs. I would have taken the carb apart by now but that's just me, I can literally put a Holley back together outside in the dark.

 

[AaronWhitt82]

Re: Carb problem or water in gas?

The accel pump gets fuel from the very bottom of the bowl where water would be, so it is odd that the accel pump gets good enough fuel to richen it up and go if there is a water problem. Let us know what the filter contents look like.

It just sounds like a main jet circuit problem to me, or a fuel bowl level/fuel delivery issue at the needle/seat maybe. Easy enough to check the bowl level if it has sight plugs. I would have taken the carb apart by now but that's just me, I can literally put a Holley back together outside in the dark.

I changed the fuel filter right before it started acting up at the normal 50 hour interval as when I usually change it.
It is just the screw on type that looks about the size of an oil filter.
I can screw it back off and dump the fuel in a container and see if I get any seperation.
I took the sight plugs out while on the water the other day and the gas was just trickling out of the holes so the floats are adjusted properly.
I've just dumped some of the red Heet into the tank and I'm going to check over a few other things on the carb, but I hate to pull it off and start tearing it apart again.
After all the work I did to it the other Summer I'm starting to know this thing inside out and have learned alot & got it tuned perfectly.
Another thing too is that the last time it rained here was maybe over 2 1/2-3 weeks ago and we had a little over 3 inches. The boat sits outside with a full cover. I'm sure if water got in from that rain it would have started to act up sooner.
The boat also sits pretty low in the water and the gas cap is in the back right hand corner on top so I'm also wondering with people getting in and out of the boat that are wet if water got in that way somehow.
I also use the boat anywhere from 2-3 times a week.

 

[Apollo75]

Re: Carb problem or water in gas?

Well, keep an open mind. If there is little or no water / crud in the filter as that is what is it installed for to catch this stuff, I would check the ignition for something breaking down or maybe a bad connection.

Check the fuel pick-up in the tank as it might be plugging up.

Sounds like fuel ---- let us know what you find


OFM

 

[AaronWhitt82]

Re: Carb problem or water in gas?

Well I got the problem fixed somehow.....
Before I went on the water Saturday I blew through all the air bleeds on top of the carb with compressed air to see if maybe they were clogged or had dirt in them.
I also put another bottle of red heet and some carb cleaner in the tank.
At first when I was launching the boat it did the same thing..... Started right up and ran a few minutes then bogged and died. Started it back up and same thing again and I pumped the throttle a bunch and then it stayed running.
Got it off the trailer and went out into the channel and dropped the hammer and sure enough after it was on plane started bogging so I pumped the throttle a bunch and it came out of it.
Well after it did that a few times then she ran perfect the rest of the day and never had a single problem so who knows what it was.

After I got her out of the water I looked at the transom and it was a little black which I thought was odd because this was the first time I've ever seen that this Summer which means it was running rich.
I was just wondering if it got black from trying to start it numerous times and pumping the throttle and revving her up that it was getting extra gas dumped in the carb.
Like I said in my previous posts the floats are adjusted correctly to where the fuel is just trickling out of the sight plugs.
I checked the air/idle mixture screws and turned them in and they were both just under 1 1/2 turns out.
Next time I go on the water I am going to turn them in just a little bit and then go from there.....
Last time I was trying to adjust them I was having problems getting the boat to idle because the idle screw was backed all the way off and it was idling around 900-1000RPM's and if I turned the idle/mixture screws in then the idle would go down, but it is idling perfect right now.

 

[Maclin]

Re: Carb problem or water in gas?

The air bleeds have to be completely open, that's for sure. Glad you are having better results now.

There is a trick that some swear by for that type of Holley, that is to get the engine up at high rpm, like 4000rpm and keep it there then cover the carb throat completely and let the engine die. This can pull any residual (and smaller!) junk on thru. I am not recommending it but some have seen the same type of carb problems as you described get better. I do not do this because to me it is way better and just too easy for me to take it apart and do a quick cleaning/blowout/refurb. I always use the blue Holley gaskets on the first rebuild, they can take several r&r's before deteriorating.