1972 johnson 50 hp carb setting

[calibassin530]

hey folks I'm new to the forums i have a 1972 Johnson 50 hp electric shift . I am having a little trouble getting my needle valves adjusted properly. I recently pulled the carbs for a cleaning,cause I was having trouble with the motor bogging down/cutting out at higher speeds, it all seemed good on the muffs and in the water first trip out. but it started running ruff the next trip hard to start then ran ok half way through the time on the water after a few hours of sitting . it was hard to start then it ran ok for while heading back to the dock at high speed then engine started cutting out anything beyond 50% throttle. it stayed running all the way back,but it would sputter or cut out when i tried to get it back up to a higher rpm. any help would b greatly appreciated thanks

 

[WhiteRice]

When you pulled the carbs for cleaning did you rebuild them with new seals, floats, needles, etc? I ask because I did the same thing and a good cleaning cannot match a good rebuild. You could have a float bowl needle sticking or a high speed jet clogged. A proper rebuild is the only way to go and I have learned this the hard way.

 

[Faztbullet]

1) Rebuild the carbs with new kits
2) You cannot correctly adjust carbs on muffs, engine has to be it barrel or lake as needs backpressure

 

[oldboat1]

Get an adjustable spark tester, open air style, and measure spark -- tests ignition output. Check compression (plugs out, crank until needle stops -- record, and move on to the next cylinder.) Hard to tell offhand -- fuel pump may need rebuilding (worn out diaphragm).

This assumes carb work was successful....

 

[calibassin530]

hey thanks for all the feed back, so when i tore the carbs apart to clean and inspect I lost the needle bearing valve. So I ordered a couple rebuild kits off amazon I don't have the part# in front of me. I didn't replace any of the gaskets or seals cause it all looked good to me. I did replace the needle bearing valve and 1 of the float bowls do to a possible crack? the kit I got didn't come with any needles is that required on a rebuild? i read about an initial setting of 1 1/2 rotations from lightly seated as a starting point?

 

[calibassin530]

i will look into getting an adjustable spark tester, is compression check a different test? what do you mean by crank until needle stops not sure of which needle you speak of? should i try these tests before or after i rebuild the carbs? thanks all

 

[calibassin530]

last question for now could i simply try to adjust the low speed needles before i tear it back apart?

 

[jimmbo]

1 1/2 turns out is the usual initial set point, final setting is always leaner, unless the float is set too low. Once set you can then reconnect the remote linkage so you can do subsequent adjustments equally to both carbs. Needle Bearing Valve? Are you referring to the actual Adjustment Needle? When you had the carb apart, did you remove the core plugs to clean out those areas? The carb kits would have included new replacements. Also when you reinstalled the carbs, you did sync the two to each other and to the spark advance?

 

[oldboat1]

I would do a compression test first, only because poor compression can indicate serious work (decision point for additional spending). The compression tester needle (if its that type) will stop rising after a few cranks, and that's the compression reading you would use -- write it down and the date for future reference. Look for cylinder readings within 10% of each other. An auto parts store will sometimes let you use a tester -- need the screw-in style. Remove both plugs for testing. No magic number -- somewhere around 120 psi would be good, but could run on less.


Spark tester is cheap. Adjustable, open air style. Weak point is the ground clip, but that is easily fixed -- make sure there is a solid engine block ground when testing. Pull out both plugs for testing (tester connects to the plug wire). Keep the tester away from the open plug hole when testing.

Don't be surprised if it takes more than one cleaning to get the carbs right. (and...could/should do needle adjustments before assuming the carb(s) have to come apart again.)

 

[Bosunsmate]

id look at the fuel pump too, take the boat out and next time she does that get someone to manually prime the fuel bulb, if that fixes it temporarily than that is your gremlin

 

[calibassin530]

jimmbo the needle bearing valve is the little plastic piece the sharp end of the needle sits in. Yes I did remove the core plugs during first cleaning. not sure what you mean by sync the two to each other and the spark advance? I took pictures and just put if back the way it was before?

 

[calibassin530]

oldboat1 I will look into the compression test and the open air spark tester will post back when I get a chance to get my hands dirty.

 

[calibassin530]

bosunmate I did replace the fuel pump along with the fuel lines in the engine area thanks all

 

[Joe Reeves]

Keep in mind that the adjustable needle valve setting on that model is for the slow speed setting only and is to be set at the lowest rpm where the engine will stay running. Those adjustable needle valves have absolutely nothing to do with the upper rpm settings.

(Carburetor Adjustment - Single S/S Adjustable Needle Valve)
(J. Reeves)

Initial setting is: Slow speed = seat gently, then open 1-1/2 turns.

Start engine and set the rpms to where it just stays running. In segments of 1/8 turns, start to turn the S/S needle valve in. Wait a few seconds for the engine to respond. As you turn the valve in, the rpms will increase. Lower the rpms again to where the engine will just stay running.

Eventually you'll hit the point where the engine wants to die out or it will spit back (sounds like a mild backfire). At that point, back out the valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest slow speed setting.

Note 1: As a final double check setting of the slow speed valve(s), if the engine has more than one carburetor, do not attempt to gradually adjust all of the valves/carburetors at the same time. Do one at a time until you hit the above response (die out or spit back), then go on to the next valve/carburetor. It may be necessary to back out "all" of the slow speed adjustable needle valves 1/8 turn before doing this final adjustment due to the fact that one of the valves might be initially set ever so slightly lean.

Note 2: If the engine should be a three (3) cylinder engine with three (3) carburetors, start the adjustment sequence with the center carburetor.

When you have finished the above adjustment, you will have no reason to move them again unless the carburetor fouls/gums up from sitting, in which case you would be required to remove, clean, and rebuild the carburetor anyway.
******************************************

When you cleaned the carburetors... If you did not manually clean the high speed jets out with a piece of single strand steel wire, do so as solvent just doesn't do that job properly. The high speed jets are located horizontally in the bottom center portion of the float chamber, way in back of the drain screws.

 

[calibassin530]

thanks for the detailed info Joe Reeves. My model has 2 carburetors and yes I did stick a small piece of wire threw the high speed jets but I did not take them out and visually inspect them. 1 or 2 questions on that low speed carb setting. I get that turning needle valve in will increase rpms and backing it off will lower rpms. but I'm a little confused, I'm i starting in idle or slightly in gear ? turning the needle valve in 1/8 segments to increase rpms, and lowering rpms by backing off the throttle closer to idle then proceeding to repeat the process until the engine spits back (sounds like a mild backfire) Then backing the needle out somewhere within that 1/4 turn for my smoothest low speed setting? sorry to b so long winded thanks again

 

[Joe Reeves]

You're looking for a smooth low rpm in Neutral.... That adjustment procedure is NOT to be done in gear.

 

[calibassin530]

Awesome thanks for clarifying Joe Reeves, finally got my hands on a spark gap tester and compression tester gonna go check it out today. I will report back with some info. I guess I'm still a little foggy on 1 thing as to adjusting the low speed carb setting. How do i separate or isolate the two carbs from affecting what I'm hearing . What I mean i guess isn't the 2nd carb gonna be messing with what I'm hearing as adjust the first, because it's still functioning or a working part of the engine? If that makes any kind of sense thanks again

 

[oldboat1]

Think that will probably be moot once you start with the adjustments. The motor will respond to whatever adjustment you are making -- if not, there is a carb issue. Get one close, then move to the second carb, then back....

 

[racerone]

Each carburetor feeds just one cylinder.

 

[calibassin530]

Ok so I'm back with a little Info compression tested at 160 on top 168 on bottom. open air spark gap tested at 7/16 produced zero spark nothing on the top plug .... bottom plug came in nice and blue with audible snaps or zaps. End of top coil plug wire connections look beat down maybe a bad wire or coil? I tried running the bottom coil wire to the top plug with no results, but the bottom on it's own fires the motor up no problem top plug was oily bottom plug looked clean ... might be on to something ?