Need help troubleshooting high idle problem.

[Eastboundndown]

Hello all, I have 350 Chevy/ with alpha 1. I have a Merc. 2bbl carb with edelbrock intake mnfld & what appears to be an automotive distributor and accel coil. Standard cap, coil is separate. I have an electric choke on carb with 1 lead coming off + side of coil and a second lead which apparently to be grounded to block. I have tried to adjust the 1 air/fuel mix screw on carburetor and have tried messing with the breaker screw on distributor as well as turning distributor itself and I can’t seem to get anything to work. Sometimes it would start at a nice idle for a couple seconds then rev right up. Any thoughts or help troubleshooting would be greatly appreciated. The electric choke and coil are getting extremely hot so I’m not sure if it could be a wiring issue or bad choke?

 

[wellcraft-classic210]

Hi
I will share a few thoughts -- the experts may have more to add.


1)--Regarding choke & wiring
Is 12 volts present at the Choke heater via dvm measurement // That same wire should not go to ground -- so retrace & post a pic if its as something is wrong.

The choke heater is supposed to warm up but if its too hot to touch I would suggest measuring the surface temp and asking the experts here.

The choke should want to close via spring tension when the engine is cold and come off as the engine warms up -- this operation and position should be verified. If a choke pull off diaphram is present it may also open up some when revved up.


2) --Regarding an uncontrolled idle that is variable // their could be a lot of causes but here are a few things to look at.

Are your throttle plates fully closing ?
Is your choke fully open & operating as it should.
Are their any vacuum leaks?
Is you Vacuum advance working as it should


__ The idle mixture screw should be set when the engine is warm with the choke fully open -- Too lean will cause a rough idle or stalling // too rich will cause black smoke should not be left out of adjustment for an extended operating period.



3) I am pretty sure you should have whats called a thunderbolt ignition -- Its a High energy system which is similar to auto's but should have a different high output coil, Dist Cap and Spark plug wire connection type , different plug wires for same reason.

Automotive parts should not be used to replace these -- Auto coils will overheat if used on a thunderbolt system

A Dist. cap type change to auto could be a fire hazard if the spark arcs to ground in places it should not & fuel fumes are present.

 

[Eastboundndown]

Thank You for input CPO

I have 12v at coil and at EC. Not sure if it will open up all the way because I haven’t been able to test run the engine because of wot like idle.. prior owner or someone but not me installed a hose adapter fitting on the top center of intake manifold between carb and distributor. So although I don’t think that is where u want vacume advance hose to go it does.. the only inlet on carb is for overflow to MFP. I do have an inlet on what I used to call air cleaner, sorry forget the boat lingo for it. I have No idea how to set the breaker screw or advanced idle.. I am starting to think that the carburetor may be the culprit. Turned The adjustment mixture screw all in and the thing is still screaming so I believe that means the carb is just leaking somewhere? Would that be an accurate accesment? One other thing that I don’t believe has any effect on my issue but just to b sure there is 1 white wire with green stripe coming off the neutral safety switch? That is not connected yet because I haven’t figured out where exactly it belongs. Thx!! For taking the time to help:joyous::joyous:

 

[Eastboundndown]

I wish I had more info on motor.. there is nothing MerCruiser left in here I feel like.. block says GM. Can’t seem to even find #s. All I have is what appears to be a marine block with accessories and everything else looks auto.. except carb. The Merc distr. don’t have vacume advanced tubes, at least the ones I’ve seen didn’t..?

 

[wellcraft-classic210]

I suspect the carb also -- Can you answer the carb questions in my post ?

Some vacuum gauge checks may be in order

You should be able to determine whats been changed in vacuum routing if anything by looking at manuals

Their are on line manuals via the " stickies " at the top of the posts


What year is the boat ?

 

[achris]

There shouldn't be a vacuum advance. If there is, that is an automotive distributor and you need to get it out and a marine one in.

Your problem does sound like a vacuum leak, coupled with the carb set too rich.

First order of business though is to get the automotive distributor out.

Chris. ...

 

[wellcraft-classic210]

Can you post some pics -- These really are car engines with a few modifications for safety & Marine performance.

 

[Eastboundndown]

Thx again.. yes I will post some pics. I will be 100% honest and tell you that I know nothing about how to test vacuum but agreed that distributor needs to go.. unfortunately.. they seem pretty pricey. Is there a certain brand or type you would recommend and is having one with coil on top better if even possible. There was dark smoke and a funky smell like an oil burner furnace smell when it ran. I took the mixture screw out and it looks like someone tightened it waaayyy too much. I will take pic of that too. And again, there isn’t anything on this boat that says MERCRUISER on it except out drive. Thx again for the guidance! Your a good egg!

 

[Eastboundndown]

[No message]

 

[Bt Doctur]

pic 1 looks like a vac hose thats plugged, pic 2 that wire used to go to the Green/White post on the T bolt dist. It is the shift interrupt

 

[Bt Doctur]

Do you need a T-Bolt ign system?

 

[Eastboundndown]

So I started posting pics and got 2 then was told I couldn’t upload anymore.. Guys I apologize but I am about as technologically savy as a peanut butter and jelly sandwich. I managed to upload rest of pics to my idea board or something like that.. can u guys see them there or can I share them somehow or was that useless

 

[Eastboundndown]

BT... That’s a damn good question? What is that? The white with green stripe comes of switch and I thought should go to distributor or coil But wasn’t sure which and wasn’t sure where

 

[Bt Doctur]

 

[Bt Doctur]

depending on your ign system, you could connect it to the neg side of the coil

 

[Eastboundndown]

BD, if that diagram is correct than I should have a distributor with 5 wires coming out of it and I have 1 black one and nothing else so I’m gonna try and find the best price I can on the proper distributor and install that, that wiring diagram is awesome, lot of help thank you very much.. everyone!! I will deal with ignition system and I’m thinking I may just want to throw a new Edelbrock 600 cfm Marine carb in, unless you guys think that’s a bad choice. I am leaning towards that one because reviews say it is reliable, almost set perfectly for 350 out of the box and there is an Edelbrock intake manifold on engine. Unless I would be better off with a Merc carb. Once I get that done if it’s not running good I will ask some more questions pertaining to vacuum.. do you guys know if I can just throw new distributor in as is out of box or do I have to adjust points gap/breaker screw? Is there more diagrams like that for the rest of system wiring.. please

 

[Bt Doctur]

diagram is generic showing the G/W wiring.If you have only 1 wire coming from the dist you have points and condensor.
The G/W wire would go to the neg side of the coil otherwise you wont be able to shift out of gear, in the water.
The is nothing to ask about the vac because vac is not used in a marine dist.
The dist may or may not come with the internals using points or electronic systems ,

 

[Eastboundndown]

But I the wrong(auto) with vac hookup distributor is in here, so How do I know what is supposed to be or needs to be here to function properly? I have more pics but I’m trying to get them on here from my idea board...

 

[Eastboundndown]

I’m pretty sure that I tried hooking the green white wire up to Negative on coil but it grounded it out and distributor would not spark.. when that switch is closed I have continuity between ground and the GW wire.. so wouldn’t that stop distributor from firing when I’n gear?

 

[achris]

Have a look for a AC-Delco 'Voyager' distributor kit for your engine. That auto dissy has to go, before... :boom:

Chris........