engine only runs with excessive choke

[roadnsky]

Agree with the boyz that you should verify timing and carb.
A clean carb with proper mixture (and timing) should only require choke for a cold start and just for a short time. (mine about 3-5 sec)

After verifying the timing and fuel, IF the issue persists...
Let's talk about your exhaust system.
Your symptoms could also be pointing to a problem there.

[Sange]

engine throttle hesitates

so the saga continues unfortunately. The carb has been re-built and installed and has improved the condition but not completely rectified. Fuel line replaced from the tank to filter to pump. The suspect cause for the choke not working was that an incorrect hose (Compressor hose was used instead of a fuel hose at one time and deteriorated, clogging the carb). New fuel filter installed. Timing and advance confirmed. Used remote tank and ships tank for testing-Ok. Everything worked fine for two hours. Went back out a few hours later and the engine hesitates from low throttle to high throttle when it's in gear. No issues when idling in neutral, throttle picks up with no hesitation. More consistent when in higher throttle but drops when lowering throttle and hesitation appears and engine wants to stall.
Next step is to install an electric fuel pump. Mechanic is lost. Also suggesting to add a lead additive to the fuel. Do any of you add lead or do most of you use MMO? Also need to check if anything is stuck on the prop/shaft so need to go diving. Thanks for all your help with this. Any other suggestions?

[capnward]

Let's clarify what it means to verify timing and advance. Did you remove the breaker plate from the distributor, inspect the advance mechanism to see if it moved freely, remove rust and oil it? When it was running ok under load, did you turn the distributor back and forth to see if it ran at higher rpm? If you had a fuel pressure gauge, you could see if pressure went down under load when it hesitates at low rpm. A vacuum gauge is also helpful when that happens. I would be surprised if an electric fuel pump solves the problem, when it was running ok for two hours with a mechanical one. Despite all you have done to clean the fuel system, your symptom of stalling at low rpm in gear still indicates a fuel restriction to me. Junk in the idle jet caused that symptom for me. Did you try enriching the mixture by turning in the idle screw a bit? I doubt if you picked up stuff on your prop shaft last time you went out. This problem has been happening for a while. I'm still not sure if you are stalling when increasing the throttle or decreasing it. Be sure to change one thing at a time, so you can learn what the problem was. I don't use lead additive, just MMO. You say you installed one new fuel filter. I have three: one Racor water separator filter, one inline fuel filter between the Racor and the mechanical fuel pump, and one inline filter between the pump and the fuel pressure gauge. My mechanical pump, which I have heard creates more suction than an electric one, seems to be able to handle all three filters. I hope your basic issue isn't so much crud in the boat's tank that two hours of running clogs filters. If you were able to run well for two hours, you are not far from success. Good Luck!

[JOHN COOKSON]

when it's in gear. No issues when idling in neutral, throttle picks up with no hesitation. More consistent when in higher throttle but drops when lowering throttle and hesitation appears and engine wants to stall.

Hesitation is a fuel starvation problem. You have an air leak or a blockage in the fuel system somewhere or crud in the carb or water in the fuel.
As a guess have you confirmed that the gas in the ship's tank is not contaminated? Pump some gas into a clear glass jar and hold it up to the light.
A fuel pressure gauge before the carburetor would sort this out real quick.

TRUE GRIT

[roadnsky]

...Mechanic is lost. Also suggesting to add a lead additive to the fuel.

That suggestion alone makes me doubt your "mechanic".
Adding lead will do about as much good as hiring a Voodoo Doctor to dance around your boat sprinkling chicken blood everywhere.

• Can you tell us the procedure you did to check the timing?
• Are you certain your plug wires are in the correct firing order?
• Have you looked at your plugs to see their condition?
• When you re-built the carb, did you use a new gasket or the old one?

As John and others have said, a fuel pressure gauge would be very valuable in your diagnosis and eliminate a lot of the guessing.

Also, I'm still wondering if you have an exhaust system issue...

[Sange]

Engine throttle hesitates

Hi Everyone - thanks again for your feedback. Let me answer a few of your questions:

1. Timing and advance - I cannot comment on the exact procedure but I double checked that my mechanic optimized this during the initial tune up in the spring and again after installing the electronic conversion kit a few weeks ago and the engine ran solid during our one week trip and we motored for 12 hours.
2. Mechanical vs Electric Fuel Pump- I doubt the electrical pump is going to make a difference as I just had the mechanical pump re-built. Reading a few comments on this forum including Don's feedback from years ago it appears that A4 owners are evenly divided and it's a matter of opinion and preference. From what I've gathered the mechanical pump is designed to pull the fuel and the electric pushes the fuel. If the electric pump doesn't make a difference I'm simply reverting back to the re-built mechanical pump. My preference is to stick with the mechanical but we'll see what happens during Monday's test.
3. Air/fuel mixture has been optimized with both the old carb and the rebuilt carb installed a few days ago. This definitely makes a difference but does not get rid of the hesitation. It is set to run a bit richer
4. Hesitation - only occurs in gear when moving primarily from low throttle to high throttle. Does not occur at the dock when running off the dock lines which is strange to me.
5. Lead additive to fuel - Far stretch and was not suggested that it would fix the problem, just suggested for regular maintenance -I will not be doing this. However, up until now I've been using Startron for the fuel. I will start using MMO effective immediately and sourced some locally here in Ontario yesterday
6. A friend of mine with the same boat C&C30-A4, also had the hesitation issue. He found an issue with the compression and 2 valves sticking. He removed the plugs and applied the MMO to release the valves. He has been treating his fuel and oil with MMO for regular maintenance and it's working for his A4. I also checked the forum and a bunch of videos and everybody seems to swear by the MMO. Sooo, I will be doing the same moving forward effective immediately. I'm also going to buy a compression tester to record the values before and after applying the MMO to quantify the condition and improvement.
7. Fuel Filters - I only have one New primary fuel filter that was installed a few days ago at the same time the rebuilt carb was installed and new fuel lines were installed. I am now going to purchase and install an in-line polishing filter and fuel pressure gauge before the carb as suggested thank you. I will try this first before adding a 3rd and need to investigate this further. Do you have a picture of your set-up with the 3 filters that I can use as a reference?
8. Brand new plugs and wires installed during electronic ignition conversion. Yes they are in the correct firing order
9. Will examine plugs and take pics when I remove them to apply MMO to the valves
10. Re-built carb - The carb was sent out to a specialty carb re-build shop and thats all that they do. I was told that they use a kit and new gaskets so trust this was done correctly. The re-built carb definitely performs much better than the other carb and my choke is now working.
11. Fuel looks clean but I have no idea if there is crud in the fuel tank. How else can I determine this simply?
12. Exhaust system issue - can you please elaborate on the issue I should be looking into?

Thanks again guys. Your feedback and questions have been very helpful and much appreciated!!
Frank

[Peter]

11. Fuel looks clean but I have no idea if there is crud in the fuel tank. How else can I determine this simply?

1) Disconnect the hose from the carb and crank the engine to collect some fuel in a glass jar (do not use a PLASTIC container - some of them dissolve in gas - I have determined this experimentally...) Examine the sample for clarity and bit and pieces.

2) Remove your fuel filter and empty it out into a glass container. Examine for crud.

3) Another less direct test is to disconnect the fuel line from the boat tank and connect it to an auxiliary tank. If the engine runs fine, strong indication of crud in the fuel in the boat tank. This is a little tricky to do away from the dock.

Hope that helps.

Peter

PS - MMO is available from COSTCO in Canada - they deliver it at no cost in a six pack for about $60

[JOHN COOKSON]

[QUOTE=Peter;113616]1)
3) Another less direct test is to disconnect the fuel line from the boat tank and connect it to an auxiliary tank. If the engine runs fine, strong indication of crud in the fuel in the boat tank. This is a little tricky to do away from the dock.
Hope that helps.
Peter

If there's curd in the carb from dirty fuel from the boats tank supplying clean fuel might not help the engine run better.
The fuel pumps job is to supply gas the carburetor at the correct pressure. The carb takes over from there.
Let's quite guessing.
STEP1: Get clean fuel to the carb from an auxiliary tank at the correct pressure. Post the results. We'll go from there.
Sorry to be so direct.

TRUE GRIT

[Sange]

Engine Throttle hesitates

During my initial post I indicated that fresh fuel was used utilizing an auxiliary tank and then the ship's tank. This was done again after installing the new fuel line and re-built carb. NO CHANGE in performance. I forgot to list it in my summary below so I've added it for reference. Next update will be after I've completed item #6&7, compression test and adding a polishing fuel filter and fuel pressure gauge before the carb. Thanks again!

1. Timing and advance - I cannot comment on the exact procedure but I double checked that my mechanic optimized this during the initial tune up in the spring and again after installing the electronic conversion kit a few weeks ago and the engine ran solid during our one week trip and we motored for 12 hours.
2. Mechanical vs Electric Fuel Pump- I doubt the electrical pump is going to make a difference as I just had the mechanical pump re-built. Reading a few comments on this forum including Don's feedback from years ago it appears that A4 owners are evenly divided and it's a matter of opinion and preference. From what I've gathered the mechanical pump is designed to pull the fuel and the electric pushes the fuel. If the electric pump doesn't make a difference I'm simply reverting back to the re-built mechanical pump. My preference is to stick with the mechanical but we'll see what happens during Monday's test.
3. Air/fuel mixture has been optimized with both the old carb and the rebuilt carb installed a few days ago. This definitely makes a difference but does not get rid of the hesitation. It is set to run a bit richer
4. Hesitation - only occurs in gear when moving primarily from low throttle to high throttle. Does not occur at the dock when running off the dock lines which is strange to me.
5. Lead additive to fuel - Far stretch and was not suggested that it would fix the problem, just suggested for regular maintenance -I will not be doing this. However, up until now I've been using Startron for the fuel. I will start using MMO effective immediately and sourced some locally here in Ontario yesterday
6. A friend of mine with the same boat C&C30-A4, also had the hesitation issue. He found an issue with the compression and 2 valves sticking. He removed the plugs and applied the MMO to release the valves. He has been treating his fuel and oil with MMO for regular maintenance and it's working for his A4. I also checked the forum and a bunch of videos and everybody seems to swear by the MMO. Sooo, I will be doing the same moving forward effective immediately. I'm also going to buy a compression tester to record the values before and after applying the MMO to quantify the condition and improvement.
7. Fuel Filters - I only have one New primary fuel filter that was installed a few days ago at the same time the rebuilt carb was installed and new fuel lines were installed. I am now going to purchase and install an in-line polishing filter and fuel pressure gauge before the carb as suggested thank you. I will try this first before adding a 3rd and need to investigate this further. Do you have a picture of your set-up with the 3 filters that I can use as a reference?
8. Brand new plugs and wires installed during electronic ignition conversion. Yes they are in the correct firing order
9. Will examine plugs and take pics when I remove them to apply MMO to the valves
10. Re-built carb - The carb was sent out to a specialty carb re-build shop and thats all that they do. I was told that they use a kit and new gaskets so trust this was done correctly. The re-built carb definitely performs much better than the other carb and my choke is now working.
11. Fuel looks clean but I have no idea if there is crud in the fuel tank. How else can I determine this simply?
12. Exhaust system issue - can you please elaborate on the issue I should be looking into?
13. Fresh fuel has been used utilizing an auxiliary tank throughout each step of this process (old carb, re-built carb) and hasn't solved the issue. No difference has been observed between the auxiliary tank and the ship's tank.

[capnward]

I wonder if the specialty carb rebuild shop uses the same kit that Moyer sells, or one with the same jets, or if they are doing something different than Moyer recommends, which might create your symptom. Probably their work is not the problem. If they know what they are doing, they know the Moyer manual. You say it runs ok at idle, hesitates on acceleration, then runs rough, is that right? If it hesitates and then runs ok at higher rpm under load, you might as well go sailing. We always hear that the engine should accelerate 'almost explosively', in Don Moyer's phrase. If that happens, then your air/fuel mixture is optimized. There are two idle ports in the upper throat of the carb, one above the throttle valve and one below. When the valve opens, fuel flows out both of them. They are small and easy to miss. Unlike the jets, you can't remove them to see if they are obstructed, you can only run a wire in them. Myself, I like to rebuild and clean my own carburetor. That way I don't wonder what someone else did or didn't do to it, professional though they may be. If the carb and fuel are clean, the jets and ports are unobstructed, the float valve is good, there is no air leak at the gaskets, and the choke works properly, your carb is good. You definitely need an inline filter, make sure it points the right way. It's probably overkill for me to have two of them, on either side of the pump, but it makes me feel better. Make sure you replace inline filters when you clean the carb. Sometimes you can tell if an inline filter is clogged by blowing through it. Let us know what the fuel pressure gauge reads, and if it drops on acceleration. It shouldn't.
MMO is your friend. The old Universal engineers whose job was to run and test these engines while they were being made also swore by it.
With your mechanical fuel pump you can use the bail underneath it to pump fuel into a glass jar to inspect for water and crud. Your primary fuel filter should have a bowl at the bottom which you can drain and inspect the fuel there, too.
I have read here about old exhaust hoses delaminating internally and collapsing inside, restricting exhaust flow but not leaking. Hasn't happened to me yet.
I have no explanation for why it only runs badly away from the dock, unless your tank is so full of crud that tossing the boat around while motoring clogs the filters, and then the jets. This is common. But then it should still run badly at the dock, until the carb is cleaned and the filters replaced. Don't let your fuel level get too low, or this is more likely to happen. I hope you are using non-ethanol gas, so water in the fuel stays at the bottom of the tank, and doesn't disperse in the fuel, bringing the crud with it, IMO. You are on the verge of motoring success here, keep at it!

[roadnsky]

12. Exhaust system issue - can you please elaborate on the issue I should be looking into?

If your exhaust is old, there are various ways it can become blocked or partially blocked which causes a "back-pressure" that chokes the engine and would cause hesitation under load.

Read this thread for a bit more info...

[Sange]

Engine Throttle Hesitation

So I had some good luck yesterday after a two week battle! The root cause of the issue appears to be the incorrect hose (compressor hose) was used for a portion of my fuel line from the previous owner, deteriorated over time and clogged the carb. Did the compression test yesterday and all cylinders were reading 100psi dry and 105psi wet with only slight 2psi variation. Through all the trial and error and issues with the choke it appears that my new plugs (3 weeks old) became fouled. I changed the plugs with an equivalent NGK BR6S that was in stock locally and the problem has been solved for the time being!! Engine is operating solid and runs smooth again and we then enjoyed a great night sailing. Will be heading out again tonight and hopefully were all set for our regatta this week. Just ordered the recommended Moyer plugs Champion RJ-12C so I have a spare on board. Will set gap at .035" per spec.
Lots of smart guys with great knowledge and experience on this forum and I would like to thank each of you for your help. Until the next time....
Thanks again - Frank

[roadnsky]

...my new plugs (3 weeks old) became fouled.

Frank-
Not to rain on your happyness...
But one should ask... why are my new plugs fouling?

[joe_db]

Dissolved hose goo????

[Cityhix]

Ye olde "only runs with the choke out" thread.

After a winter spent rectifying the effects of the boat partner not shutting off the raw water intake when cranking the motor with no start, I finally took the boat out for a sea trial today.

Work done since last Fall:

-rebuild carb
-rebuild raw water pump
-rebuild heat exchanger
-new coil
-new points, cap, and rotor

The motor has been running fine at the dock, in neutral and in gear. In fact, it sounds better than ever. Today I took it out for a motor in fairly rough seas. Just off the dock it was purring along fine and then quit with a "starved for fuel" type shutdown and restarted immediatley. Ten minutes out into the bay it quit again and then started back up readily. Fifteen minutes later, it quit again and started reluctantly then gradually required full choke to run and we returned to the dock with no further shutdown.

Things that I will do before heading out for the coming weekend:

-Turn in the idle air screw to enrichen the mixture a bit.
-Change main and secondary fuel filters.
-Order a new fuel pump.

Any other suggestions?