carburetor suspect problems

[lukecono]

Given the older style ignition module present I'll note if the sensor in the distributor has been replaced with the latest style sensor I've experienced a timing jump at idle of anywhere from 4-8 degrees. This would account for the varying rpm at idle speed you're experiencing.

I cannot tell from the photos if the setup has a newer style sensor

Couple things I do see in the pics is the throttle return spring is installed incorrectly and the plug wires are wire tied in a bundle on the odd side

Can you elaborate on the plug wires being tied in the wrong spot and also the throttle return spring? I'm a young lad here trying to learn as much as possible!!

 

[lukecono]

The reason the choke is zip tied open is the aftermarket aluminum intake does not have the choke stove capability in the exhaust cross over. Quadra jets liek this use a divorced choke with a heated spring in the manifold. Someone removed this. A place like cliffs carbs should have An electric choke conversion or advance the throttle on cold starts .

i ran my mercarb with choke forced open for years was onky an issue starting in cold weather in the fall

The cylinder heads do have a small port open still to run an electric choke, but my issue now is if the wires on that side of the carb have 12v still running to power the electric choke and then also if there is a hole running under the carb for it to read the temperature off of. Does anyone know of the proper parts I would need to do the setup with the electric choke and housing missing on the side of the carb to have the choke go into. I'm barely understanding the concept of how this electric choke, and where, it will read temperature to react accordingly.

 

[Scott06]

The cylinder heads do have a small port open still to run an electric choke, but my issue now is if the wires on that side of the carb have 12v still running to power the electric choke and then also if there is a hole running under the carb for it to read the temperature off of. Does anyone know of the proper parts I would need to do the setup with the electric choke and housing missing on the side of the carb to have the choke go into. I'm barely understanding the concept of how this electric choke, and where, it will read temperature to react accordingly.

an electric choke does not need the hot exhaust gases to open a hot air choke does. Here is a short article on choke styles.

What Kind of Choke Do I have - Mikes Carburetor Parts

What kind of choke do I have. There are 4 different types of choke systems. Learn about the choke that you have.

www.carburetor-blog.com

an electric choke uses 12v to heat up a bimetal spring in choke housing when off the spring is cold and when stabbing the throttle the choke 'sets' and closes. Once engine is started and running 12 v is constantly supplied to the choke element and over a few minutes it heats up and opens the choke. The choke gets hot of the 12 v not engine temp.

Since some one converted your intake to a aftermarket aluminum one there is no provision in the cross over for the hot air choke stove (element), so you have to either force the choke open and live without one or get a electric choke conversion like this

Divorced Choke Electric Conversion Kit - CU1444

www.carburetor-parts.com

A place like mikes - carburator-parts.com or Cliffs https://cliffshighperformance.com/

can walk you through what you need to put an electric choke on it.

You also can pump the throttle a few times to squirt some gas in there before starting and then just let it warm up at fast idle... I ran my boat for years like this. Isn't really an issue in the summer only fall and early spring when its cold. Not really an elegant solution but works...

 

[lukecono]

an electric choke does not need the hot exhaust gases to open a hot air choke does. Here is a short article on choke styles.

What Kind of Choke Do I have - Mikes Carburetor Parts

What kind of choke do I have. There are 4 different types of choke systems. Learn about the choke that you have.

www.carburetor-blog.com

an electric choke uses 12v to heat up a bimetal spring in choke housing when off the spring is cold and when stabbing the throttle the choke 'sets' and closes. Once engine is started and running 12 v is constantly supplied to the choke element and over a few minutes it heats up and opens the choke. The choke gets hot of the 12 v not engine temp.

Since some one converted your intake to a aftermarket aluminum one there is no provision in the cross over for the hot air choke stove (element), so you have to either force the choke open and live without one or get a electric choke conversion like this

Divorced Choke Electric Conversion Kit - CU1444

www.carburetor-parts.com

A place like mikes - carburator-parts.com or Cliffs https://cliffshighperformance.com/

can walk you through what you need to put an electric choke on it.

You also can pump the throttle a few times to squirt some gas in there before starting and then just let it warm up at fast idle... I ran my boat for years like this. Isn't really an issue in the summer only fall and early spring when its cold. Not really an elegant solution but works...

Thank you for those links and clarifying!! I wasn't aware that the electric choke makes it that easy! The carb part number is MCM 1347-8292 and finding that kit for the electric choke wasn't easy. I'm going to go ahead and check those links you shared with me and see if I can get what I need and make quick work of this. I have been using the boat with this process of the progressing and pumping throttle but takes quite a while and when it does start make sure im not going from nothing to 3 GRAND on the rpms and blowing something up lol. The choke should make this consistent!

 

[Scott06]

Thank you for those links and clarifying!! I wasn't aware that the electric choke makes it that easy! The carb part number is MCM 1347-8292 and finding that kit for the electric choke wasn't easy. I'm going to go ahead and check those links you shared with me and see if I can get what I need and make quick work of this. I have been using the boat with this process of the progressing and pumping throttle but takes quite a while and when it does start make sure im not going from nothing to 3 GRAND on the rpms and blowing something up lol. The choke should make this consistent!

Would make sure your ignition components are up to snuff. If ignition is good, the littlest bit of gas will fire off. Might also fatten up the idle screws or at least try adjusting them to see if it helps.

Dont be intimidated by the carb they are inherently simple, just takes some experience and time messing with them to get a feel for it

 

[lukecono]

Would make sure your ignition components are up to snuff. If ignition is good, the littlest bit of gas will fire off. Might also fatten up the idle screws or at least try adjusting them to see if it helps.

Dont be intimidated by the carb they are inherently simple, just takes some experience and time messing with them to get a feel for it

I don't see how the ignition components could be not functioning properly as everything points to this and how the boat does fire consistently in the same range of attempted cranks. All of the components on the engine for starting are newer and all internals. Can you confirm to your knowledge that kit would work that you shared the link for on my carb? There's like 6 different electric choke set ups!

 

[Scott06]

I don't see how the ignition components could be not functioning properly as everything points to this and how the boat does fire consistently in the same range of attempted cranks.

A working choke will help but the phrase below implies that spark may be weak but your call

but takes quite a while and when it does start

I cant confirm what kits fits your carb best to contact sellers and give them your carb number or discuss with them

 

[lukecono]

A working choke will help but the phrase below implies that spark may be weak but your call



I cant confirm what kits fits your carb best to contact sellers and give them your carb number or discuss with them

If spark was weak wouldn't the engine run funny. Please correct me if that isn't the case. Also, what would be an appropriate way to see if that was the case?

 

[dave8311]

Is there supposed to be a return spring on there?

 

[lukecono]

Is there supposed to be a return spring on there?

supposed to vs can you not sure, I had it on last two engines when purchased.

 

[Scott06]

If spark was weak wouldn't the engine run funny. Please correct me if that isn't the case. Also, what would be an appropriate way to see if that was the case?

I have had ones that run decent but are hard to start. Seen it on a couple where I didn't realize spark wasn't perfect, replaced some parts and noticed a big improvement in how quickly they started. Seen this on an old 2 stroke Evinrude 15, my 65 GTO, and most recently when I repowered my boat. The TB V ignition amazed me how strong the spark was w/ blue spark vs orange. Any of these engines the smallest amount of gas off the carb and they fire right up choke or no choke...

I would get a spark gap tester and make sure you get a good spark that can jump a good gap. They are like $15. you can visually inspect the cap and rotor, ohm out the coil and wires, check or replace the plugs.

 

[lukecono]

I have had ones that run decent but are hard to start. Seen it on a couple where I didn't realize spark wasn't perfect, replaced some parts and noticed a big improvement in how quickly they started. Seen this on an old 2 stroke Evinrude 15, my 65 GTO, and most recently when I repowered my boat. The TB V ignition amazed me how strong the spark was w/ blue spark vs orange. Any of these engines the smallest amount of gas off the carb and they fire right up choke or no choke...

I would get a spark gap tester and make sure you get a good spark that can jump a good gap. They are like $15. you can visually inspect the cap and rotor, ohm out the coil and wires, check or replace the plugs.

Thank you I can go ahead and do that also. Quickly though if you are familiar do I need a choke housing to run an electric choke or is that only for hot air choke where I need the housing?

 

[dubs283]

Can you elaborate on the plug wires being tied in the wrong spot and also the throttle return spring?

The plug leads should not be bundled together, that can increase the chance of cross firing. They should be allowed to hang free from each other and not tied together with the casings touching. If a couple of them cross lightly thats okay but tied together can be bad. They are mercury brand wires manufactured in early 2017 based on the date code. Good wires but still 6 years old and bundled together

The throttle return spring attaches to the bottom portion of the throttle cam and attaches to the throttle cable anchor bracket aft of the carburetor. This will achieve the same effect as the current position, an aid to keep the throttle stop resting against the idle speed screw

Have you checked your idle timing or confirmed the vintage of the ignition sensor in the distributor?

 

[tank1949]

I have an early 1980s MerCruiser 5.7 and the boat takes a while to get running. I have to pump and advance the throttle multiple times (from 5-15 tries) cranking with no life until it fires up and must maintain 1500 rpms before bringing the throttle down to idle and not having it stall. The engine is still under 20 hours of run time since being freshly built by certified mechanic. The engine isn't stock and does have an aftermarket cam rods and pistons making 300hp instead of the 260. The other funny thing is that the boat does decide to idle at different rpms. Typically, after bringing the throttle back to neutral after waiting a few minutes at the 1500 rpms it'll sit at 900 rpms idle, I shift, and it drops to 700 rpms... that's the normal part. After on plane and coming off back to idle the boat again goes to 900 in gear and slowly walks itself down to its lobing 500-700 and stays there once in neutral. My biggest thing is having it start within first couple tries and my first suspicion is not enough fuel until that 10th try or so cranking. I haven't dug into it too much, but I think one of first places I should look is at the fuel accelerator pump and see if fuel sprays when I give it those priming throttle pumps. ANY thoughts?

I have electric chokes on my Edelbroks. However, Quad0jets are good carbs as long as they remain clean inside. I learned a long time ago that sometimes internal passages get crud in them. A mechanic showed me a trick to remove some of this crap w/o tearing apart the carb. With throttle linkage removed, water hose attached and fire extinguisher nearby, advance carb to 2500 RPM and slowly put your hand to cover butterflies. This will cause a suction that might free up crap. The motor may start to stall. So if it starts, remove hand and repeat. I did this several times back in the day on muscle cars. This is an old hot-rodder trick that worked many times. However, not all the time.....

 

[lukecono]

I have electric chokes on my Edelbroks. However, Quad0jets are good carbs as long as they remain clean inside. I learned a long time ago that sometimes internal passages get crud in them. A mechanic showed me a trick to remove some of this crap w/o tearing apart the carb. With throttle linkage removed, water hose attached and fire extinguisher nearby, advance carb to 2500 RPM and slowly put your hand to cover butterflies. This will cause a suction that might free up crap. The motor may start to stall. So if it starts, remove hand and repeat. I did this several times back in the day on muscle cars. This is an old hot-rodder trick that worked many times. However, not all the time.....

Great tip I can try that for sure thanks!!

 

[lukecono]

Hey guys! Issue is solved and this is what was going on. I appreciate all of the inputs and thoughts. First of all, my choke was removed on carb and zip tied open. Not a big deal in the summer. Secondly, my fuel accelerator pump was sticking for first couple of throttle advances.

Now neither of those was the big deal but eventually everything led to spark. My mechanic and also the one who built the motor came over and was doing his rounds until we couldn't get it to start at all. After it all he grabbed the coil, and it was burning hot and visibly cooked. He took off top plug and the cooling oil was visible out the top. He then felt around more, and my Thunderbolt 4 module was burning hot as well, and he believed it shouldn't be that hot that can't touch. We replaced coil just because easiest route and that didn't solve the problem. Bought a used module and put it in and boat fired immediately. I had aluminum spacers between the module and the manifold that mechanic said to be safe and replace with the nylon spacers to avoid whatever made it so hot, besides the excessive cranking. Also now have rubber insulation inside the coil bracket too. Had boat out last couple days turnkey no issues but had one last question... After returning to dock I felt around everything, and the module coil and distributor were all pretty warm. The engine room and 90-degree day make it hot in there and not to mention its next to the exhaust, but is this normal for these components, and the entire engine to be hot? All of my electrical checked out before replacing this module and coil.

Thank you again everyone

 

[Bondo]

After returning to dock I felt around everything, and the module coil and distributor were all pretty warm. The engine room and 90-degree day make it hot in there and not to mention its next to the exhaust, but is this normal for these components, and the entire engine to be hot?

Ayuh,..... Normal operatin' temps are well above comfortable to the hand,....

 

[lukecono]

Ayuh,..... Normal operatin' temps are well above comfortable to the hand,....

Meaning?? I can hold my hand on all of those components but are warm.

 

[Bondo]

Meaning?? I can hold my hand on all of those components but are warm.

No worries then,....

 

[lukecono]

No worries then,....

Great, mechanic checked all wiring for ground outs and back feeding just so same issue doesn't happen again so when I felt any heat wanted to double check. Thanks again!