popping from carb

I'm a new member and a new owner. I just rescued a 1980 Ski Nautique that had not been off the trailer in 10 years. After washing the green off the entire boat I rebuilt the carb and cleaned the points. The boat runs but not well. I cant get it to idle under 2k and when it is loaded (in the water vs running on the trlr) it pops through the carb. I'm suspecting timing but I am at a loss. Ant ideas? I have cleaned and lubed the weights in the distributor and they don't seem to be stretched. I also posted this in the general section accidentally. Woops. Rookie mistake

I'll check the timing tomorrow. I found tdc #1 and followed the firing order listed on the tag on the intake and the cylinder numbers stamped on each runner. Where should the timing be? I will hit it with a light tomorrow.

Also could be vacuum leak. Spray carb cleaner around base of carb. If that changes RPM, you are onto something.

The above suggestions are all good. I will add the following:

Leaking exhaust manifold or riser gasket.
Sticking intake valve or a burned valve.
Broken timing advance spring in the distributor.

Art

The high idle and backfire are symptomatic of an intake system vacuum leak. One thing to check is the PCV valve to make sure it has the proper amount of restriction in it. You can simulate the high idle situation by removing the PCV hose at the base of the carburetor. Typically with that fitting open, it won't idle below 2000.
Art

Were you able to idle it down enough to properly set the base timing? If you set the timing with the engine running at 2000, no wonder it does't run right! I believe, from memory, that a 1980 with Ford (PCM or Commander) should be set at 10 degrees. There will be a highlighted mark on the vibration damper indicating the proper base timing.

Art

ArtCozier wrote: The high idle and backfire are symptomatic of an intake system vacuum leak. One thing to check is the PCV valve to make sure it has the proper amount of restriction in it. You can simulate the high idle situation by removing the PCV hose at the base of the carburetor. Typically with that fitting open, it won't idle below 2000. Art

+1, Art.

My other boat has an old Mercruiser 140. I suffered through a few years of high idling and lousy starts. I eventually found a vacuum leak due to an aged carb gasket. A new gasket helped a lot. Then I had the carb rebuilt (I'm not good with small parts), and for a decade now that 40 year old four-popper has been idling smoothly at spec.

Steve

You're absolutely right Art.
At 2K RPM I'm guessing the timing should be at least 20 degrees, maybe even a bit more.

Do just as Art recommends to set the timing with two hands as you get the idle lower and the timing decreases.

Also, what did you set your point gap at? That will change your timing and therefore your idle too. Should be .019".

Eddie Backfoot is spot-on about the points. I'll try to look in an old owner's manual and check the point gap recommdation. Actually, you should be able to find one on "Reference" on this site!
Art

.018 or .019. That's splitting hairs.
Either one will get you running so that you can time it properly.

I was worried you had them set to .025 or .015 or something crazy like that.

i finally had a chance to mess with the boat... I removed the choke to look inside it for gunk. For fun I covered the hole where it gets vacuum and the engine idled like a champ. Huh? Where is the common area for a vacuum leak inside the choke housing? The gasket appeared good.

Sorry. I should have said that. Yes it is electric. The wires get a key on voltage. I haven't seen it work properly (move the butterfly) to date but it was lower on the nitpick list than the boat running so I had overlooked that. I took the cap off of the choke housing and it looked pretty clean inside there and the piston moves easily. I haven't messed with an electric choke before so any help would be great. I found a replacement cap at the parts store but they aren't as cheap as I was expecting so I hate to buy one if I possibly don't need to.

I did note that the tang was around the coil so thats step one... I will try the operation of it this afternoon. I checked the voltage the other day and it was only 9v. The battery might be low though due to cranking. (although it did turn the engine at a normal speed) I will charge it tonight and check again tomorrow.

the choke is getting 9v with the points closed and 10 volts with them open. the coil is getting the same voltage. annoyingly the other side of the resister is only getting 4v. So it appears that the choke is hooked to the correct side of the resister. The batt has 12+ volts. Im wondering of the choke has not worked in awhile. The main issue I have is the vacuum loss mystery. Could a malfunctioning or low voltage choke cause a vacuum leak? Also unfortunately I messed up the gasket on the choke so I at least have to buy a cap. Where does the red wire originate that goes into the harness loom on the top of the engine?

Is the 4v on the "other side" of the resistor with the points open, or closed? If it's points closed, it's probably OK. It should go to a bit under battery voltage when the points are open.

A malfunctioning choke will have no effect whatsoever on engine vacuum. Once the engine warms up, the choke is out of the picture anyway. Of course the vacuum will still be applied to the housing. I guess they do that to keep the choke from overheating.   

I don't think there is any opening into the choke housing other than the vacuum port. If the gasket is good, there should be no airflow into the choke housing, and therefore the engine won't get extra air via the choke. Could it be that the housing gasket was failed to begin with? If there is a speed shop (hot-rod shop) in your town, you might be able to buy that gasket as a separate item there.

Let's test the choke heating coil off the engine. Just run 12v and ground with small jumper wires to the terminals on the cover. Watch the "coil" in there for at least two minutes and see whether it starts to move. You might have to put a clear glass dish or something similar over the open side of the choke housing to retain the heat. If you leave it completely open it might lose enough heat to keep it from operating properly.

The purple wire on the choke housing comes from the ignition switch, via the "high" side of the resistor. Here is what the circuit looks like: Starting from the terminal on the starter relay where the red battery cable connects, battery current flows from there to the ammeter, then through the ammeter. (<Your boat does have an ammeter in it as opposed to a voltmeter, right?>) From there, a red wire goes from the ammeter to the "hot" side of the ignition switch. When you turn the switch to "on," the red wire is connected to the purple wire coming out of the ignition switch. From there, it lands on the "high" side of the resistor, where the wire to the choke stove also is connnected.

Now, all of the wire mentioned above will cause a certain amount of voltage loss. There are two occasions when ignition current has to pass through the 8-prong plug at the right rear corner of the engine where the engine harness plugs into the boat harness. Unplug that plug (it might be taped up. Take off the tape.) Get some fine sandpaper and clean up the prongs on the male side of the plug. Then roll up a little piece of sandpaper and clean the holes on the other side. Use an in-and-out motion to sand the inside of them. It is very common for those prongs and receptacles to have corrosion on them, resulting in a voltage loss.

If voltage loss is causing your ignition system to have weak spark, you can try this: Run a small jumper wire from the "high" side of the resistor to a source of 12v. (the engine end of the + battery cable is good. It's on the starter relay, remember?) BE CAREFUL that you don't hit anything grounded with the jumper while is't connected! You don't want to be welding! Start the engine with that jumper in place. REMEMBER that with the jumper in place you won't be able to turn the engine off with the ignition switch. You will have to have the switch off AND the jumper disconnected.

I didn't get a chance to have a look at a carburetor today. Hopefully tomorrow!