Surging!

WhiteLakeSkier wrote: Anything to do with vent tube? my tanks tube does not run to the outside of the boat. It comes out an inch or so and ends.

Letting gas fumes vent into your bilge is a bad bad situation. Don't go boating again until this is fixed.    You are lucky to be alive!    Get that vent run to the outside of the hull.    Drill a new hole & run the hose out if you have no other option.

Can't help with the surging, although it does sound like a carb problem.

Nothing to do with idle mixture screw right? I had to lean them out since I had quite a smokey exhaust. they are less than 5 turns out. Common sense tells me Idle mixture deals only with idle but hey I might be wrong.

I did set them by going 1.5 turns out, then adjusting. I didn't remember exactly what they were at for reference, but I knew they were less than 5. But none if that relates to the surging I suppose.

So, the carb isn't getting enough fuel. Why doesent it just run that way all the time instead of surging? I mean it seems that if something was stuck in the tank pickup, it would be starved of fuel continuously until it went through to the filter, and would just run continuously bogged out?

Where should I begin looking? Can it be said the problem is not the carburetor for sure and I have to look at what's before it?

two problems,

first stumble, adjust the accell pump until you get a steady stream from the get go, this can be done without the engine on, also it might require a new accel pump in the carb, but asjust first if you can't get a full stream for the full stroke, then replace.

the next issue is fuel delivery.

Bad fuel pump, or anti-shipon valve, but just get a new pump and I bet that fixes the problem, Fix the vent correctly too, has nothing to do with it unless it's clogged.

So fuel pump, test with gauge to verify bad 5.5 lbs min.

Clean antishipon valve,

make sure vent is clear and connect to the outside.

If fuel pressure is good, valve is clean and vent is clear and you still have the problem, raise the float.

Alright sounds good. Now how do I check the accl pump and adjust?

I'm guessing its either the anti siphon valve being plugged, or the fuel pump.

Even if the accel pump was bad, it wouldn't go from 4k to 3k with no change in throttle.

Now a bad fuel pump could do it too, but start with the cheap (actually free0 check of cleaning the anti siphon valve. Now the vent line, well that really is important.

The anti siphon valve is right where the fuel line is attached to at the top of the fuel tank. it's brass,and threads into the fitting on the tank.

Many people, including myself have chased their tail by not checking this. Had I known there was one, and that they get clogged from time to time, I would have saved myself a lot of work,time, and money.

Granted if I just fixed that, I would only have 240 hp and not 300+hp like I do now.

That just screws onto an elbow. I really don't think mine has any valve. When I did this boat, I left the original 12 gallon tank in there with these copper lines.

I adjusted the accl. pump by tightening the nut. Is that the direction to adjust if you don't think your getting a constant stream?

Yesterday while I was out fooling with it, It bogged down till stall and ended with a little backfire of sorts. Started back up afterwords however.

Now to test the fuel pump, I have a harborfreight fuel pump/vacuum tester. Can I just screw directly into the top of the fuel pump and crank it over? I can't just splice in with it being a metal line.

WhiteLakeSkier wrote: 79nautique wrote: The kicker is that it pretty much tops out and then has issues, thus a low float and no fuel in the primary bowl causing it. . Check float level now?

Sorry if I sound sarcastic but yes check the float level now, you're getting advice from a pretty good source so oblige and do what he says.

Next time you're going to sit down and bake a cake here's a little reading for you to familiarize yourself with Holley carbs

There are also tons of articles on holley carbs all over the web so take a few minutes and do a quick search, it will be worth your time.

WhiteLakeSkier wrote: No it wasn't sarcastic at all. I trust the source believe me. I'll get reading, unfortunately no cake in the oven.

Good, you show promise grasshopper.

Float adjustment, remove front bowl by loosening the four bowl screws, to prevent spilling fuel all over your intake remove one bottom screw fully and try to catch the fuel in a small cup then wipe any spill with a rag.

Remove the bowl, flip it upside down so you are looking at the float. Holding the bowl level, the float should sit level with the top(now bottom because your holding it upside down) if it's not level bend the tab connecting the float to the needle valve with a small pair of needle nose pliers until the float is level. Minor bend is all it should take.

Seems pretty level. Do I need to bend it down to make it a bit more level?


Unfortunate I broke the gasket. I assume no napa or anyone would have something like this on hand, so it will be a few days before I can try this out. Now when I pulled it apart, it came a little violently. What does that little brown arm attach to. Am I missing anything in these pictures? I don't see that I lost anything but carb parts are pretty small to spot on top of the engine or elsewhere around the boat.

Alright, I shall see what I can find at napa. So just leave the brown arm hanging when I put it all back together. The thing looks like it has a purpose, but hey I have seen plenty of pointless engineering.

That float does look a tad tow to me as well. The angle of the pic actually makes it look close to level, but if you were to have the bowl completely level in the picture, the float would look even more "low".

Now that copper/ brown piece I am pretty sure just goes to the other "pin" just on the other side of the center that the one side is hanging from.



Absolutely napa or other places will have that gasket in stock, and make sure to get the blue ones because those won't stick, and you can reuse them without worrying of them breaking like the original type.

If that is a 4 barrel with a transfer tube and single fuel inlet, then you will want to buy a couple o rings for the transfer tube while you are at the store. I would get a new accelerator pump diaphragm as well since you are in there and the front bowl is off.


79, yeah, i did miss a little bit there, but I can say from my own personal experience that as the anti siphon valve gets clogged, it will allow it to rev even at full throttle for a while, then it will just shut off after the restriction doesn't allow the pump to get enough fuel to the bowls.

On mine, it progressively got worse and worse after a couple of seasons.
when I first got my boat I could go slaloming with no issues. Then the duration it went before acting like it was running out of gas got shorter and shorter. Slower rpm cruising like wakeboarding never gave the motor an issue because the restriction was not enough to go over the amount of fuel demand that was needed for 2100 rpm. eventually that rpm limit and duration of time before it "ran out of gas" got lower and shorter. I figure that was due to more crap getting stuck int he anti siphon valve and it ended up building up a blockage too much to get gas past for more than idling. There were a bunch of bees/ wasps in my anti siphon valve from many years of it never being cleaned. A lower psi pumping fuel pump probably contributed tot he lack of gas delivery too, and I bet the old pump may be needing rebuilding because it wasn't able to get gas into it all the time. I'm guessing no gas in the line won't do anything to help a fuel pump's longevity.

Whitelake, you may not have an anti siphon valve, I don't know when that safety measure was added as a factory thing.

if you have an O'reilley's or Advance parts store they sould carry them too.

new fuel pump marine. Not sure but some model fuel pumps are rebuildable others are disposible.

get a new fuel pump, leave the float alone for now, no sence in creating another problem, now if you have moved it all ready leave it for now amd we'll see what happens.

but get the new fuel pump installed, reset the idle mixture screws using a vaccum gauge attached to the port for the PCV, engine warmed up and then check base idle while in gear adjust accordingly. Double check your accel pump it should start squirting fluid almost immediately the throttle lever is moved, adjust the nut until it does, if it does seems to help and looks worse then turn it the other way until you get the full stream for the entire stroke of the throttle.

This isn't a Mastercrap. Just stupid stickers were all over it from the PO. Couldn't I check this by running the engine off a separate tank? I'm not sure how this thing sucks up fuel, but it can't be too complicated. It would be a real pita to get the tank out again and take it out. For sure an idea I'll have to look into though if it runs well off a separate tank.