wont stay running

[icy]

i have a 73 135 hp johnson that seems to run good, but only if you choke it.. as soon as it runs out of fuel from the choke it dies.. the fuel bulb is pumped up, and pumping it while running does not help.. am i looking at a carb rebuild or maybe a fuel pump, or something else i havent thought of? the fuel lines appear to be in good shape with no cracks..

 

[ezeke]

Re: wont stay running

Pumping the bulb would get the fuel to the float bowls regardless of the fuel pump, so that it not the problem.

If you give the carburetors a good cleaning, by the book, I think that you will solve the problem.

 

[F_R]

Re: wont stay running

Most likely, the high speed jets (orfice plugs) are dirty or gummed. They (four of them) are in the very bottom of the carburetors, deep behind the hex plugs, where the last bit of fuel lays and turns to gum. ANY gum at all will cause your problem. Those orfices have to be absolutely, positively shiny brite clean with no trace of anything in them. Clean the carbs thoroughly and you will fix the problem.

 

[burroak]

Re: wont stay running

Been there, done that!

Just got a 73 135 evinrude running after a long storage time. Ezeke's advice is the short story probably, but after rebuilding the carbs and you may still have issues. Nothing big, but things I had to account for to get the 'rude dude running smoothly.

Note: When you rebuilt the carbs, run a #68 drill through the low speed idle jets. It was impressed upon me that the #68 drill should be used, no more or no less. I got mine at a hobby store.A little jeweler's vice will hold the bit and allow it to turn. blow out the orifice with compressed air.

 

[ezeke]

Re: wont stay running

Don't know where you got that but it is interesting to know why.

The idle orifice is a 317473, or # 30 or .030 in size. A # 68 drill bit is .0310 in size. Running a ever so slightly larger bit through that old orifice would [1] assure that the size was at least the original standard .030 and [2]maybe a little larger won't hurt to allow for the alcohol in the fuel. A #69, at .0292 would be too small, and a number #67 bit at .032 is too large.

To take it a step further, you could look at the high speed orifice, # 318657 at .073 and fit a bit to that. A number 49 is exactly .073 and should fit exactly.

Be sure that the carburetors are the 1973 ones. They changed, and the orifices are not the same from year to year. To be sure of the jet you have to see what is stamped on it, as well as measure it.

 

[icy]

Re: wont stay running

ok, i understand about jets and such, but will the high speed jets really affect the not idling.. just a thought.. does anyone know if the jets happen to be the same size/thread as the jets in an automotive holly carb? i have lots of extras of those laying around since we are not racing anymore.. I may have to take a look at that since it would seem simple to replace an old jet for a new one that way. So it seems that a carb rebuild is the way to go for this thing?? It is of unknown history since i just aquired it and will be in need of a good decarb when its running decent. Is there something i may be missing that would make it not idle?

 

[ezeke]

Re: wont stay running

Most likely thing is that the idle jets and/or the capillaries leading up from them to the floor of the carburetor throats are clogged. The jets are behind the 4 brass screws on the lower outsides of the barrels.

The capillaries exit behind the throttle plates and near the intake manifold so that when you close the choke the pistons' strokes can pull the fuel through.

Carb cleaner, sprayed with the tube, through the 4 idle orifices after removing the four brass screws will sometimes free the gum and allow the carburetor to function well enough to isolate the problem and keep the motor from stalling. You can tell if it is working if you can look down the barrels and see the cleaner spraying through the several holes in the floor of each throat.

At some point the carburetors have to be broken down and thoroughly cleaned to get the motor running properly, AND, to protect the engine from running lean and being destroyed.

 

[ezeke]

Re: wont stay running

BTW, no one actually takes those jets out of 30+ year old aluminum carbs unless they have to, because if you screw up and lose the ears on them, you just lost a carburetor. The better bet is to measure them with the drill bits so you know you have the right ones, and clean them from the oposite ends like the manual says.

If you think you have a problem now, try matching a set of those carburetors on short dollars.

 

[iwombat]

Re: wont stay running

Fine, NOW you tell me.


Mine came out and went back in just fine though.


:%

 

[icy]

Re: wont stay running

woo hoo!! I finally had some time tonight to go out and play with this thing. After a proper dose of carb cleaner (2 cans!!) and a small amount of tinkering i did get it to run and idle.. Moved on to decarb now.. its sitting for the night.. will let you all know how it all turns out!!

 

[icy]

Re: wont stay running

Ok, I went out tonight and tried to start the ol girl. She cranks and cranks but not so much as a cough tonight.. when i pull the plugs and ground them to the case i show only having spark in 1 cyl. could running the seafoam have ruined the spark plugs to the point that they wont spark? I didn't think to check without the plugs in the boots till after dark-thirty.. Or is it possible that I have a different problem now.. it was running decent last night and tonight nothing..

 

[Kevin70]

Re: wont stay running

A can of Seafoam should come with new spark plugs. If you used a lot of it, you should put some new plugs in. I fouled two of four plugs on my Volvo-Penta, but it was well worth it.

 

[icy]

Re: wont stay running

ok i learned the hard way.. seafoam in the motor, dont use new plugs.. it WILL kill them... new plugs in the motor and it fires right off...