58 Evinrude 7.5 hp stalls when choke is pushed back in

[dancamp009]

I have a 1958 7.5 HP Evinrude long shaft that didn't run and had the old fasion dual gas line when I got it. Because it had compression and spark and I didn't have the original dual line gas tank, I converted the old style two hose system to a new one hose gas line the way they tell you how to do it at www.outboard-boat-motor-repair.com.
I get it running fine until I push the choke back in and then it conks out. I've cleaned the carb, adjusted and cleanded the points, get good spart, so I think it's in the gas line.
At first I became concerned because it didn't appear to be providing any suction (if anything it appeared to be pushing air out of the intake manifold) to pull the gas through the new fuel pump (Mukumi like in their picture). So I moved the plug from the left hole to the right hole behind the intake manifold to see if that would help create suction as it may have worked as now it will idle at high speeds while the choke is pulled out. It does smoke alot however. But as soon as I push the choke in, it stalls out nomatter how much gas I give it.
Another point. The fuel line conversion instructions call for adding single line fuel connectors (male and female) to the fuel line going from the tank into the fuel pump. I haven't yet bought the fuel line connectors, believing it should be fine temporarily just going straight into the fuel pump from the hand pump hose attached to the gas tank. Am I right in this assumption? Yes the gas tank is vented. Am I wrong? Are those inline fuel connectors neccessary to build up vacuum or to make the pump work correctly?
Any advise on this issue would be much appreciated.
thank you
DanCamp

 

[F_R]

Re: 58 Evinrude 7.5 hp stalls when choke is pushed back in

If it continues to run as long as the choke is pulled out, that indicates there is a blockage in the carburetor. The fuel pump is supplying gas as far as the carburetor, or it wouldn't continue to run with the choke out.

Revisit the carburetor. Pay special attention to the slow speed needle and transfer ports under the welsh plug. Did you put in new gaskets?

 

[dancamp009]

Re: 58 Evinrude 7.5 hp stalls when choke is pushed back in

thanks for rapid response
Hope what you say makes sense. What is the welsh plug, however?
Is that what fits over the slow speed needle, which I presume is the top needle?.
And no, I didn't replace the gaskets in the carb, just sprayed through the ports with carb cleaner sray and caught a couple rubber gaskets by accident.
I'll get new gaskets Monday, and see what happens. Looks like good news so far though. . .
thanks for the help.
dancamp

 

[dancamp009]

Re: 58 Evinrude 7.5 hp stalls when choke is pushed back in

on second thought, if the carb is getting enough gas from the fuel pump, then why do I still have to squeeze the hand hose bulb pump and spray starter fluid into the carb before it will start?
I've fiddled with the top needle valve so much it's getting silly. I've got the needle jacket bolt as snug as possible with still being able to turn the needle.

 

[F_R]

Re: 58 Evinrude 7.5 hp stalls when choke is pushed back in

You didn't mention having to squeeze the bulb. Of course you have to squeeze it to fill the carb for initial starting, but do you have to keep doing that to keep it running even with the choke on? That would make a difference in the diagnosis.

The welsh plug is a small round disc on the top of the carburetor. Sometimes called a "freeze" plug or "core" plug. There is a cavity beneath it and several tiny holes that the idle fuel has to go through.

Once in awhile somebody will twist off the tip of the idle (slow speed / upper) needle in the carb body. The needle is supposed to have a sharp point. Does it?

How did the coils look when you had the flywheel off? If they are cracked you are wasting your time dinking with the carburetor. Matter of fact, 90% of carburetor problems aren't carburetor problems at all. Your mention of having to use starting fluid raises serious suspicions. The coils in those old OMC motors are always bad, unless they have already been replaced. And it is usually blamed on the carb. "Tain't the carb.

 

[dancamp009]

Re: 58 Evinrude 7.5 hp stalls when choke is pushed back in

i've confused you.
I only sqeeze the bulb to get it started, and then shoot starter fluid into carb. sometimes I have to clean the plugs too with starter fluid. But it usually takes starter fluid to start it.
Once started, it runs at a million rpms, until i get it under control, with the choke valve and slow needle adjustment, and last time it ran for at least a minute on it's own until it peuked from pushing in the choke.
I think it's fouling the plugs a little, even though it has 75 LBs compression.j
tell me this, should that hose coming from the intake manifold be a strong continuous vacuum, or perhaps a little pulsating? Because last time I checked, it pushed air, but that was before I moved the plug into the other port hole under the intake manifold. Haven't checked since, since it idled for one minute on it's own for the first time in my history, even though the choke was pulled out.
The coils and plugs look GREAT, nice strong blue 1/2" jumping spark too.
thanx again

 

[F_R]

Re: 58 Evinrude 7.5 hp stalls when choke is pushed back in

The fuel pump requires a pulsating pressure / vacuum pulse to move the diaphragm back and forth. That is what does the pumping. The piston moving back and forth in the cylinder causes a pulse in the crankcase, which is what is being used to operate the pump. Just pressure or just vacuum won't work. It has to be a back and forth pressure / vacuum.

Sounds like somebody has already got in there and replaced the coils. That's good.

 

[F_R]

Re: 58 Evinrude 7.5 hp stalls when choke is pushed back in

I failed to mention that if there is gas in the carburetor, it should start easy without nursing it with starting fluid and run at least until the gas is used up out of the carb. The fuel pump has absolutly nothing to do with it except for replenishing the gas in the carb as it is used. If you are having to use starting fluid, either the carb is plugged up or there is something else wrong. Did you use new gaskets on the reed plate when you had it apart? A leak between the upper and lower chambers will keep it from running.

 

[Chinewalker]

Re: 58 Evinrude 7.5 hp stalls when choke is pushed back in

First things first - DITCH THE STARTING FLUID! You'll kill your motor!

Next, you should have one of the holes in the intake plate plugged off so that the pump is operating on only one of them. Each hole runs to one side of the crankcase. The up and down motion of the piston provides the plus/minus pressure pulses needed to operate the pump. Easiest way to see if the pump is working is to prime the bulb up, then remove the fuel line from the pump to the carb at the carb and run it into a coffee can. Attempt to start the motor. If working properly you should get a repetitive squirting of fuel into the can as the pump pushes a little fuel in with each revolution of the motor.

If that is happening, then your issue is with the carb. Completely disassembly and clean it, blowing out passages with compressed air and carb cleaner. Remove the plug as F_R noted. Also, check the float - if the lacquer finish is checked or cracked, consider resealing it or replacing the float. OEM plastic floats for 1970s era 6hp carbs will work just fine.

- Scott

 

[tashasdaddy]

Re: 58 Evinrude 7.5 hp stalls when choke is pushed back in

this is why i'm agaist the conversion of the old pressure tank, to fuel pumps. why mess with proven technology. this is the best carb adjusting i've ever used. just sold a '55 15 hp rude that ran like new

http://www.iboats.com/bbboard/bbBoard.cgi?a=viewthread;fid=28;gtid=818798;gpid=818802


parts are also available at laingsoutboards.com

 

[dancamp009]

Re: 58 Evinrude 7.5 hp stalls when choke is pushed back in

Thanks you guys, I certainly appreciate all your help. The good news is that I'm an idiot and have to admit it. I took off the carb to clean it out again and replace all the rubber gaskets and found the 5 or 6 screws that hold the bottom to the top were "LOOSE". How in the hell I allowed that to happen is beyound me, but I did. So I retightened them and put it back on, put new plugs on, and, finally, only after one last light sqirt with the starter fluid (which I hate to do but couldn't get it started otherwise), it started up and ran for five minutes with the choke closed and even at a pretty low idle considering. My only problem now is ALL the HORRIBLE SMOKE that it emits. I know the 50 to 1 oil ratio is correct as my Mercury 7.5 runs fine on this ratio, but it still smokes like hell. I've tried adjusting both screws (bottom backed out about a 1/4 turn if that) and the top one backed out 1 1/2 turns and then back into all the way down, which does effect it's idling, but doesn't reduce the smoke.
Just for kicks, I've included two photos to help diagnose my problem. The first points to what I believe is the welsh plug (freeze plug or core plug) you are referring to. Am I suppose to remove that plug too, or just clean around it on the inside? Could this plug be causing my excessive smoke problem?
Also, the second picture shows three holes along the starbird side of the motor. I imagine these holes are for attatching something to the carb. Are they fine the way they are?
By the way, both needles appear to be fine with nice clean points.
Thanks again guys
DanCamp009

 

[F_R]

Re: 58 Evinrude 7.5 hp stalls when choke is pushed back in

That is the welsh plug. It has absolutly nothing to do with the smoke.

Forget you ever saw the other holes. They have nothing to do with your motor.

50:1 IS NOT the correct mix. 24:1 is.

It will smoke. A lot. It's supposed to. That's the way it was in those (good old) days. It won't be so bad on a boat, but in a barrel it will fog the mosquitos for miles around.

 

[dancamp009]

Re: 58 Evinrude 7.5 hp stalls when choke is pushed back in

Thanks for the mix info. After rereading my manual, I see that you are right on the proper fuel/oil ratio. I assumed when the manual said to use Evinrude 50/1 Lubricant, that meant a 50/1 ratio. But looking closer, they say 1956-1963 2-strokes get a 24/1 ratio, while later years (64-72) get the 50/1 ratio. This will probably add to my smoking problem too.
I'll tinker with it some more, get some new gas, change the gas mix, take that carb apart again, check the float closer, and see how it goes.
thanks again guys for all the help,
enjoy the game
dancamp009

 

[dancamp009]

Re: 58 Evinrude 7.5 hp stalls when choke is pushed back in

GREAT NEWS, got it running like a real sweet heart. Bought some new gas and oil, rebuilt the carb again, this time more in depth like you guys advised, threw away the starter fluid, and BAM! She started up on the second pull and ran like a champ ever since, nothing like the smoke before either. Really got her running smooth.
So the carb definately needed a better cleansing and having new gas didn't hurt either, besides all the rest of the repairs thanks to all of you. Whew, now I can sit back and watch the game, go boating, and forget about all this engine repair, until next time I find a used outboard anyway. . .
Thanks again you guys and have one on me. You deserve it.
dancamp009

 

[tashasdaddy]

Re: 58 Evinrude 7.5 hp stalls when choke is pushed back in

when you get it in the water take a copy of the of Joe's carb adjustment with you and tune it in really good. mine never spit, sputtered, coughed or sneezed, after using that method.