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1975 Johnson 50 HP outboard motor lack of power

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lohrdg

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I just bought a 1975 Johnson 50 HP (50ESL75B) outboard motor. It starts right up and idles fine. Starting out it seems to run ok for a bit then seems to bog and then power drops to near idle with the throttle wide open. It will also sputter and appear to be lacking fuel. Once it is off for a few minutes it runs fine for a few minutes then problem reoccurs. It has sat for a year but had a tune-up and carb rebuilt by a reputable marina before being winterized. I have added a new fuel line as well. Any help would be appreciated.
 
Was old fuel left in tank mixed with fresh fuel?IF so dump contents, clean tank,possible fuel pump malfunction,check pressure with gauge, air leaks in fuel lines ,check filters,fuel seperator etc.If these tips do not work start with troubleshotting101 compression test,spark test, etc.
 
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I was having a similar problem with my 74 50hp. The fuel tank was not vented and it was starving for gas. I now just crack the fuel cap slightly to make sure it's vented.
 
My '74 50hp Johnson did the same thing. It turned out that the tank was not vented and it was starving for fuel. I now keep the gas cap cracked open a bit to make sure.
 
Fresh fuel, clean tank, replace fuel pump, no air leaks in fuel lines, compression (ok) and spark test (ok). Carb floats were out of adjustment, corrected that. Ran for 20 minutes wot then started acting up again. Someone mentioned it could be electrical like a stator issue, but not sure. Any help is appreciated.
 
Electronics can sometimes breakdown when high temperatures are met,check coils with ohm meter if possible when still warm or hot,Pull plugs when symptoms occur check condition,wet,black carbon fouled,lite tan running good
 
How can I check to see if the waterpump is working properly without dropping the gearcase. Is it just as simple as if water is flowing out of the pee holes it is good?
 
Try holding hand on head for a six second count,no burn your ok. Just because water is flowing out is no indication engine is running at proper temp.
 
Does the water only come out the exhaust housing at the mounting bracket or should it also come out from under the motor case? How long should I have it run before checking the water with my hand?
 
after engine has warmed up fully,you should be able to hold your hand indefinitely in water stream.Water should exit out of prop also through hub if equipped.The issue we are trying to diagnose is engine running hot and ruining electronics,stator, coils etc. heads can be checked with a digital infrared thermometer,found one for 20 bucks. I gather u don't have a temp. gauge?
 
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Great. I really appreciate your help as I know engines just new to marine engines. I'll try this tonight. Is there a way to hook up a temp guage? If so, what's the best way to do so?
 
Finally back to working on the motor. Replaced the water pump and engine remains cool. Someone told me to try to run the engine with only 1 of 2 cylinders. Ran engine in lake and took one plug wire off and engine ran ok. Reconnected it then pulled other plug wire and engine stalled. Does that indicate a coil problem?
 
no spark on first plug wire pulled, motor running on one cylinder only, electrical problem but check compression first and report numbers
 
lohrdg said:
Ran engine in lake and took one plug wire off and engine ran ok. Reconnected it then pulled other plug wire and engine stalled. Does that indicate a coil problem?
Click to expand...

You don't say which cylinder had its spark plug wire pulled that allowed the engine to continue running. Which one was it? If it made absolutely no difference in the performance of the running, it was not operational at all! Did it make any difference and if so, what?

You also mentioned that the compression and spark was ok..............

That doesn't mean a great deal to many of us. What is the actual psi compression reading of each individual cylinder?

With the spark plugs removed... The spark should jump a 7/16" air gap with a strong wide blue lightning like flame, a real SNAP! Does it?

Without this information, it's all guess work and time and money wasted.
 
How many cylinders is outboard? What cylinder is not firing? Have you tried swapping coils? Was compression tested with a good guage& spark tested with the joe reeves method,dry gap,big blue lighting snap! We need answers from you so we can help u.
 
Compression tested at 145 -150 on each cylinder. The spark test looked good at 7/16". The top cylinder was the one with the issue. Swapped coils and the problem stayed on the same cylinder. This only appears when the engine has ran for a few minutes and at 3/4 to full throttle. Thinking maybe an stator or sensor coil issue when the get warm? How can I test that?
 
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