1964 3HP Carb Question

[Rainyday101]

Hi,
I have been rebuilding a 1964 3hp Johnson. The motor was given to me for free and had sat along time. The owner said this motor had less than 24 hours on it. Completely replaced the ignition system to include coils, condesors, points, plug wires, and plugs. I have plenty of spark. Also replaced the water pump and prop. Rebuilt the carb, but I am having problems starting it. I cannot get it to fire unless I spray brake clean directly into the carb. It will run about 10 seconds and quit. When I was rebuilding the carb, the gasket that sits on top of the high speed nozzle was to thick to bolt the carb halves back to together. I had to file it down a bit to get the carb back together. Maybe it is not making a seal/filed down to much? The original gasket was black rubber and was badly deteriorated. The new gasket was brown, thicker, and much harder material. When rebuilding the carb, I replaced the float, float seat, gasket between the carb halves, intake gasket, gasket as described above on the high speed nozzle, and the needle valve packings. I thoroughly cleaned the carb with air and brake cleaner to include all the passages. The engine is a JH19A. The engine has plenty of spark. Here is the link to the parts page for this carb.

http://www.marineengine.com/parts/vintage-evinrude-johnson/380044/catalog.html?http://www.marineengine.com/parts/vintage-evinrude-johnson/380044/38004400001.htm

Any help or ideas would be appreciated.

 

[1946Zephyr]

Re: 1964 3HP Carb Question

I would check the fuel flow coming out of the gas tank. These areas can plug up too.

 

[lindy46]

Re: 1964 3HP Carb Question

That seal should be thick. I usually have to tighten the float bowl bolts to compress it.

 

[Rainyday101]

Re: 1964 3HP Carb Question

I did check the fuel flow from the gas tank and it was originally non-existent. I cleaned the the strainer filter that is soldered in the tank to get it clear, then cleaned the valve and fuel line. I do have decent flow now and am getting fuel into the float bowl. I am going to get a new gasket for the high speed nozzle and see if this will work. I contemplated tightening the carb halves to crush this a little, but the gasket I recieved was really hard and would not compress. I am guessing that maybe this gasket was old and had hardened up.

 

[Rainyday101]

Re: 1964 3HP Carb Question

Last night I replaced the high speed nozzle gasket and also found that the plug at the bottom of the float bowl with the small orfice was plugged. Cleaned that up and put the engine in a water tank. Engine started right up. The problem now is that the engine will run on choke, shut the choke of and the engine will run about 3 seconds until you have to pull the choke out again. The engine starts to run rough on the choke and you push it in and keep repeating this process to keep the engine running. I am thinking that the float bowl is emptying and not refilling. That is why it only runs a short time untill you have to choke it again. So now I am back to that soldered in strainer in the fuel tank. Despite cleaning and cleaning, I can not get a consitent fuel flow. What is the best way to get this thing out of the tank? I know if it was soldered in, it should be unsoldered, but is that safe with a fuel tank?? Even taking the fuel out leaves ignitable fumes. Has anyone else taken one of these out?? Could it be drilled out??

 

[lindy46]

Re: 1964 3HP Carb Question

Running lean. Have you tried opening up the low speed needle and see what happens? Is that strainer soldered into the fuel tank or is it attached/soldered to the valve? Seems i remember on my older 3hp the strainer was attached to the valve and the whole assembly came out together. To see if it's a problem with that strainer, you could rig up a gas supply in a small container with a hose, and connect it to the carb directly. Hold the container above the carb and see if it runs.

 

[Rainyday101]

Re: 1964 3HP Carb Question

I will try opening up the low speed needle valve some more. I had it at about 1.5 turns out. the damn strainer is soldered right into the tank and is not attached to the fitting that threads into the tank. Your idea with a seperate fuel supply is exactly what I was thinking about doing. That should narrow down the problem real quick. If that works it is the strainer and I will have to get it out and just use a small inline filter. Would you try drilling it out? It is soldered in just below the threads for the fitting that screws into the tank. I would have to be extremely careful not to damage the threads.

 

[Rainyday101]

Re: 1964 3HP Carb Question

Okay, I about give up on this carb. I am getting enough fuel from the tank. I took the carb apart for the fourth time and cleaned every passage again. I removed the round pounded in seal on the top of the carb and checked all the orfices under there and cleaned. Pounded a new plate seal in. Tank tested and same thing. The only way I can keep the engine running is to cycle the choke in and out. Tried at all speeds same thing. Adjusted the mixture control from one and half turns out to three turns out, no change. What am I missing???? Help!!!! Reed valves???

 

[lindy46]

Re: 1964 3HP Carb Question

Could be an air leak/small crack in the carb. May be invisible. I had a 5.5hp engine and had similar problems - just couldn't get it to run right. Rebuilt and cleaned several times. I finally got a replacement carb and she purred like a kitten.

 

[JohnRudeMan]

Re: 1964 3HP Carb Question

Okay, I about give up on this carb. I am getting enough fuel from the tank. I took the carb apart for the fourth time and cleaned every passage again. I removed the round pounded in seal on the top of the carb and checked all the orfices under there and cleaned. Pounded a new plate seal in. Tank tested and same thing. The only way I can keep the engine running is to cycle the choke in and out. Tried at all speeds same thing. Adjusted the mixture control from one and half turns out to three turns out, no change. What am I missing???? Help!!!! Reed valves???

I have exactly the same problem (cycling the choke in and out to keep it running) with my 1960 Johnson 3hp.
Is the compression on your motor right? On my motor it's very low... I have to put a new head gasket on it to get good compression .

 

[nwcove]

Re: 1964 3HP Carb Question

did you clean the passage that feeds from the bowl to the area under the welch plug? if so, try sealing the welch plug with clear fingernail polish. if its sucking air from anywhere it wont run right.

 

[Rainyday101]

Re: 1964 3HP Carb Question

JohnRudeMan, I have not checked the compression because it seemed fine, but I will put a gage on it and check this weekend.

nwconve, I hate to sound stupid, but what is the welch plug? Is that the removeable plug with the orfices under it that is tapped into place?

 

[nwcove]

Re: 1964 3HP Carb Question

yes thats the plug, there are 4? tiny holes under it, and a passage that comes up the side of the carb . if that passage is full of crud the motor cant get fuel up to the low speed jet. or if it leaks air around that plug it will not work as its supposed to.

 

[Rainyday101]

Re: 1964 3HP Carb Question

The passage from the float up to the area under the welch plug is clear, I can spray cleaner and air through it. The ohter holes were cleaned in the same manner. I sealed the welch plug with finger nail polish. I am still getting the same result. If I run the engine with my finger covering about two thirds of the carb intake it will run fine. I conclude- starving for gas or sucking air. The float bowl is clean and I have checked, cleaned, and run air through all the passage at least 5 times. This pretty much leaves sucking air! What about those passage ways on the exterior of the carb that are plugged by the rubber black titties? I assume those were for machining access. Have you ever seen these go bad?

 

[nwcove]

Re: 1964 3HP Carb Question

rubber black titties? you must be referring to the leadshot plugs, and ive never heard of those falling out or leaking.....but its a possibility. could it be sucking air around the throttle plate shaft? as lindy mentioned, the thick rubber gasket that goes on the bottom of the high speed jet should keep the bowl from mating to the carb until you tighten the screws. ( found that the sierra kits come with a gasket that is way to thin and just wont work)

 

[Rainyday101]

Re: 1964 3HP Carb Question

I will check around the throttle shaft. I got a replacement gasket for around the high speed nozzle and that seems to be fine. I can see where it has mated and compressed when I take the bowl apart. I am going to go through every passage way and the rest of things on this carb with a maginfying glass and push monofilament fishing line through every passage. I will look really good around the throttle shaft.

 

[Rainyday101]

Re: 1964 3HP Carb Question

PROBLEM FOUND!!!!! While looking at the carb closely with a magnifying glass I noticed what appeared to be a deffect or scratch in carb throat from the air intake side. This is in the top half of the carb. Looking at the other side of the carb from the top of the float bowl side you can see a similar defect. With a magnifying glass you can see that is a casting defect. Despite this defect from both sides it looks like at one time there was a sliver of aluminum casting sealing this defect. Now that extremely thin piece of casting in the defect has a small crack in it, and with a light a magnifying glass you can see right through it. I think I will try a small dab of metal epoxy and try this again.