mercruiser will not plane 220HP chevy v8 305

[NHGuy]

Carb guy.
Jeez, I hate posting from a phone.

 

[NHGuy]

So, I have a minute.
If it's a quadrajet. The accelerator pump ball seat can lose it's ability to seal. My carb guru's book says you take the old check ball and reform the seat shape by taking a flat tipped punch and hitting/tapping the old check ball. Then toss it for the new one. That will assure your carb gets a squirt when you try to accelerate.

There is another harder thing that needs doing on qjets. It is to remove the Idle tubes so the passage they are in can be really cleaned out.
The tubes have collars at their tops and are press fit into the carburetor right next to the venturis.
To be able to grip them you use a small flat tipped punch to drive the inner tube down around 1/8 to maybe 3/16". Then to remove them get a sharp tipped deck screw, grind off a little bit of the tip and use the screw to grab onto the inside of the brass collars.
Then, and this is important, use a flat piece of metal against the carb body and a set of side cutters. Grab the screw with the side cutters and lever the tubes out using the flat piece of metal to spread the leverage and avoid distorting the carburetor body.
After those tubes are out you can really clean the circuit.
I have a picture, I'll post it to show where those tubes are.

 

[NHGuy]

pic

 

[lihartke]

We had no power issues before the rotor and cap replacement and mechanics said we had power after that but once the carburetor was "rebuilt with kit and new float" we had no power and it pops and dry carbon fouls the plugs. Honestly I think the carb is not set properly. We picked boat up tonight from mechanic after he made an " adjustment" and I swear all he did was turn the idling down! Now, it pops as soon as u accelerate instead of after a little while of accelerating. Gonna spend the darn $350 and take it to someone who will actually rebuild it properly and get it right not sure what carb it is all I know is it is a 1979 2 barrel chevy small block 305 v8 220hp if that helps. Can't wait to see what the new spark plugs look like tomorrow

 

[lihartke]

Anybody know of a good carburetor mechanic inbuffalo ny?

 

[lihartke]

So we checked the plugs and they were black but we really only started it up and left the dock and redocked. So we checked the air/gas mixture screw to see where that was set at and it was set at 2 1/2 turns from all in. We checked the idling screw and that was set at 2 turns to all in. So, we put them both at 2 turns from all in. We took it for a ride and no popping on immediate acceleration like yesterday. We drive at low idle for 1 hour and it still popped a little while trying to plane. We turned the screws both 1/2 turn towards all in went to the river and was able to get on plane, pushed through some popping and put throttle fully down. Water was calm and at full throttle I am missing about 10mph. It did stop popping for the most part. Not sure if there is carbon in there it needs to get rid of, or it still has issues. I am lacking speed so I believe it has issues. The problem with my mechanic is that his hours are not condusive to getting your boat looked at with full attention. I didn't realize rhe carb was as important to set right as it was, or I would have left it with someone that had the time to make sure it was correct and had water by them to run it on a full load to test it. Will rich fouled plugs clean themselves if the problem is fixed? Will the engine burn the carbon off? I am hoping when I pull them out they are clean and my problem is solved. Any chance?

 

[alldodge]

Black plugs in most cases is from running rich, popping is from incorrect timing or running lean. If it runs lean then the plugs would be white. If the motor ever starts running right then the plugs will clean up so long as there not so clogged up they won't even fire. A wire brush can clean them up.

Check your timing and if you have points check them also. Pull the distributer cap off and check what it looks like again

 

[Rick Stephens]

Note: idle mixture screws only adjust the mixture when the throttle plates are fully closed. Once the throttle plates are cracked open a tiny amount, the mixture screws no longer effect carberation. Setting idle mixture screws is only done when the motor is at idle and only effects mixtures at idle.

Adjustments to the mixture in any other throttle position, from barely opening through full throttle is done by changing or cleaning ports, passages, needles and jets as well as float height (and possibly fuel pump pressure). These adjustments are typically part of a carburetor rebuild with the assumption being that the needles and jets were already calibrated for that motor.

Carburetor rebuilds are the most often incorrectly done job across the entire spectrum of motor mechanics. It takes care and attention to details. It is the easiest to miss a small passageway or port or bit of debris waiting to block something. Usually a poor rebuild ends up being a lean problem, but is is entirely possible to leave float height too high or a spring out and make things too rich. I have heard that incorrectly done carburetor rebuilds approach 60%. Not sure if that is a valid number, but I'd believe it.

Rick

 

[harleyman1975]

No Rick that was me and that was a 60% success rate over the course of my life LOL! Seriously though have a real carb guy soak, clean & rebuild that puppy...or buy a new or rebuilt unit from a reputable seller. make sure it is electric choke too. We can tell you how to hook it up. Sooo much more trouble free once set. Hang in there we will help you get things straightened out.

 

[lihartke]

I do have an electric choke. The dustributor was redone but not the points. I guess the cap could be slightly misaligned but it is definitely running rich and has little power. The carb guy said it was rebuilt but I do see black stuff under the top set screw that looks like it was there for quite a while as if it wasn't cleaned. This is so dejecting. Biat mechanic is on vacation for 13 days! note to self: get a mechanic who works during summer and vacations in winter and who does not own a boat

 

[KJM]

its a long shot but try cleaning the spark arrester on top of the carb as well. I was recently having problems I thought were fuel related and the realized the spark arrester was so clogged up a light put inside it couldn't shine out thru it. I soaked it in gas and cleaned it real good and boat worked fine this weekend. I know the seal around the arrester/ carb interface probably isn't airtight but it was causing the engine to be starved for air I think. if you remove the fuel line as it enters the carb and get lots of gas when you turn the engine then it probably isn't the fuel pump.

 

[harleyman1975]

it is totally possible that the carb was only partly rebuilt or rebuilt incorrectly or set incorrectly...I know I have done it myself more than once. the two barrel rochester carb is pretty simple but still has its idiosyncrasies. I stand by my advise to find an older experienced auto mechanic and have him go through it again. only thing that can cause it to run rich is the carb. if it is lugging or stumbling in a consistant manner that could be timing but it would be constant...not come and go.

 

[lihartke]

Is it possible to adjust the carburetor for "running rich" or is that something you have to take it all apart for?

 

[alldodge]

Is it possible to adjust the carburetor for "running rich" or is that something you have to take it all apart for?

If it was running rich only at idle, then yes
With it running rich above idle no

 

[lihartke]

Hmmnn? I'm not sure if it is running rich above idle because I ran it in the canal at less than 5 mph mostly. It's definitely running rich at low speeds. It is "popping"'as soon as I try to get on plane and when I am on plane although it does get better the faster I go. I took it to a boat mechanic so here goes a few hundred $'s but atleast they'll get it right. I know they know what they are doing. Thanks for all your help!

 

[Rick Stephens]

Timing and or Carberation. Best of luck with your repair!

Rick

 

[harleyman1975]

Hope you get a little use out of it this season!

 

[lihartke]

Well, i did get on one vacation and got a couple hours in it even if it was trying to restart it and ran it in the canal a couple hours. I just hope I get it fixed to winterize it. I don't want to open it up next season and gonthrough all this again. Hopefully next years trip to the k islands will be succesfull cuz the last 3 haven't been.
Gonna keep on boating on