4hp johnson

[ramboot]

Having problems with my 4hp Johnson new plugs, wiring fuel pump rebuild and carb adjusted< I cannot get it to stay running unless I work the choke out and in., then runs for a time at half choke but will never stay running. The guy who looked at it didn’t know what he was doing? Because I sure don’t. Help?

 

[Crosbyman]

sounds like it is starving for fuel (you did not specify year or model)

have you checked the hose and connector for air leaks have you opened the tank vent if so equipted

does it run better if you keep squeezing the bulb if yes maybe the rebuilt fuel pump is still bad


is it the pump you rebuilt or the carb ??? did you just adjust… the carb or completely cleaned it and reassemble it ??

btw… compression ok and you have good sparks ??

 

[lindy46]

Could be as simple as opening up the slow speed needle a little.

 

[ramboot]

Thanks for the responses guys, will check this out. Not sure what model, it’s a 70’s weedless prop unit

 

[oldboat1]

Don't think we've been asking as often for model numbers -- but should. See if you can find and post a number so the year and particular model won't be in question.

 

[ramboot]

Looks like there is a number on the carb, 386183 or 81, hard to read, another number386297, first number might be a 2, then one number on the inside of the cover is 2512. Can anyone tell me what year of this Johnson seahorse is? So I can look for parts.would it be expensive just to put new carb and fuel pump in?

 

[oldboat1]

If in fact a 4hp from the '70s, look for a four digit number: 4W followed by the year (4W75 = 1975).

 

[racerone]

Picture of the motor and cowling might identify the year in about 2 seconds.

 

[ramboot]

Does this hel;p< cause I cant find a model number

 

[oldboat1]

Motor has been repainted or touched up, but the metal ID plate is visible on the motor mount in the first picture. See if a model number is visible or can be made visible.

 

[ramboot]

Thanks, I removed the paint and behold there was the info, model 4w75a and serial # 19954, also I remembered cleaning a lot of black residue from the small holes on the shaft, is that from a fuel problem also?

 

[Crosbyman]

great little kickers did you do or try anything from post #2 or #3

do you see water spitting out the back series of holes when it runs on choke ??

 

[racerone]

Yes the paint and cowling are for a 1975 model.

 

[ramboot]

I haven’t had a chance to do anything with it yet but will this week end, yes I am sure there was water or mist of water coming out of the holes

 

[racerone]

The motor will keep running if it overheats.-----Nothing to warn you or stop it.--------Install a new impeller now if you do not know the age or condition of it.------Just 4 small bolts and a few screws for the pump housing.------Also lets you grease the upper spline of the driveshaft / crankshaft to prevent failure there.

 

[ramboot]

Thanks for all the replies guys, I have taken the carb off and completely toe apart and cleaned, put in new plugs, fuel pump rebuild, changed out impeller and greased spline, tested compression and both cylinders were exactly 90.
opened needles 1 turn from closed, choked and pulled a couple times and away it went. Still running rough but I have no idea where to start on adjusting the needles, should I have started at 1-1/2 turns open and turn back, and which one do I tune first, the fast idle (top) or the rich/lean (bottom)

 

[hardwater fisherman]

Look at the top secret files under the heading how do I adjust my carbs.

 

[oldboat1]

Adjust idle (top needle) first. From initial 1 1/2, close 1/8 at a time until you get a lean sneeze or stall, then c.clockwise (richer) 1/4 turn. This should be close to what you need. Throttle down when adjusting leaner (clockwise) as rpm will increase. Should idle at about 650 rpm, give or take, warmed up and in gear. Need to be able to shift from N to F or R without stalling without any throttle adjustment.

High speed needles are usually set to about 1 turn open or less initially, then adjusted at WOT or thereabouts on the boat. Reset the idle after the h.s. setting is determined after the boat run.

 

[hardwater fisherman]

^^^There are no gears on this motor. It is direct drive.

 

[Crosbyman]

page 104... red book see url on top of picture

at idle....top needle turn it out till it starts to bog from excess fuel

screw it in till it chokes from fuel starvation

find the middle point … maybe a bit on the rich side

wait a few minutes between small adjustments


at running speed …

do the same with the bottom needle