old johnson 4hp issue

Z

Zaworski

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Hi boating people....i have a early 70's johnson 4hp outboard...it runs great all day trolling but when i run it a higher power maybe half throttle and higher it quits and wont restart until it cools off. It just slowly dies. I have cleaned the carb, put a fuel pump kit in it, installed new points capaciaters plugs and leads, when it dies it still has fuel; the bulb is hard and i checked at the carb. I have also installed a new water pump. There is always water shooting out the water hole but im not sure if its enough. I suspect im having a heat related problem. Has anyone had a similar issue and what was the problem? Also does anyone have any pointers as what to do next?
 
oldcatamount

oldcatamount

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Re: old johnson 4hp issue

Check the water inlet screen in the lower unit. You'll find that the screen is made of fine mesh and sometimes will get clogged with small particles of debris in the water. This has happened to my 4hp a couple of times.
 
Z

Zaworski

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Re: old johnson 4hp issue

oldcatamount said:
Check the water inlet screen in the lower unit. You'll find that the screen is made of fine mesh and sometimes will get clogged with small particles of debris in the water. This has happened to my 4hp a couple of times.
Click to expand...

Thanks for the quick reply....i dont think that is the problem im having as i have cheked the screen...
 
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Crosbyman

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Re: old johnson 4hp issue

are coils replaced or still using the old ones (cracked) ??


tried running it with fuel tank cap off ....?? if ok with no cap on the tank the air vent is clogged.

check for spark WHEN NOT RUNNING .....if spark ok then fuel problem
spark not OK => ignition failure (rework ignition..test coils,etc..)
 
Z

Zaworski

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Re: old johnson 4hp issue

Crosbyman said:
are coils replaced or still using the old ones (cracked) ??


tried running it with fuel tank cap off ....?? if ok with no cap on the tank the air vent is clogged.

check for spark WHEN NOT RUNNING .....if spark ok then fuel problem
spark not OK => ignition failure (rework ignition..test coils,etc..)
Click to expand...

I have ran it with the fuel cap off it makes no difference...the motor will run for hours at trolling speeds but at high power settings it only runs for a minute or so then it dies with or with out the fuel cap on..it still has spark but absoulty will not start until it completly cools off...im having a real brain teaser here..
 
Z

Zaworski

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Re: old johnson 4hp issue

I forgot to mention i have also replaced the ignition coils.....
 
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raczekp1

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Re: old johnson 4hp issue

are you sure, motor is not overheating?
can you put hand on powerhead?
 
Z

Zaworski

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Re: old johnson 4hp issue

raczekp1 said:
are you sure, motor is not overheating?
can you put hand on powerhead?
Click to expand...

Im not sure if its overheating...i never tried to put my hand on the power head..im not sure how hot they should run..i will give that a try next time i get a chance..just so im clear, should i be able to hold my hand on the power head? Im assuming the power head should be warm not hot?
 
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bonzoscott

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Re: old johnson 4hp issue

Some have said you should be able to put your hand to the head as long as you want, others say 3-5 seconds. I think if it is over heating, it will burn you pretty quick. I think it is a carb or pump issue. Sounds like it's draining the bowl.
 
R

Rick.

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Re: old johnson 4hp issue

Not sure of your year but the older (late 60's and 70's don't have a thermostat and consequently run very cool compared to motors with stats. Even my 80 has no stat but I've no idea if they added them later. You should be able to hold your hand on the top of the head for a four or five count easily. If you have time when it is starting to die pull the choke out some and see if that keeps it going. All good advice above also. Sounds like you have done a lot of part replacement already. Best of luck. Rick.
 
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Crosbyman

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Re: old johnson 4hp issue

ok .. what about oil mix ratio ...seems like it is heating up ( is it for sure ?) so it must be friction (bad oil ratio... try more oil and/or seafoam to decarb properly)

or low cooling...could be clogged water passages (sediments) have you pulled the powerhead to at least inspect the watre jackets, the water passage and proper head gasket positioning (cooling holes lined up ?) . Try flusing water up the water tube with a garden hose to see if any restrictions are apparent (before pulling the powerhead)

btw have you inspected reeds ?
 
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Z

Zaworski

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Re: old johnson 4hp issue

Crosbyman said:
ok .. what about oil mix ratio ...seems like it is heating up ( is it for sure ?) so it must be friction (bad oil ratio... try more oil and/or seafoam to decarb properly)

or low cooling...could be clogged water passages (sediments) have you pulled the powerhead to at least inspect the watre jackets, the water passage and proper head gasket positioning (cooling holes lined up ?) . Try flusing water up the water tube with a garden hose to see if any restrictions are apparent (before pulling the powerhead)

btw have you inspected reeds ?
Click to expand...

Thanks everyone for the tips...ill do more troubleshooting and post the results...no i have not checked the reeds and i have not pulled the power head..i think i will try the garden hose and see if i can find a porblem then run it again and see how hot it is...thanks again...
 
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Crosbyman

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Re: old johnson 4hp issue

keep pressure down from the garden hose ...flush gently but sufficiently
 
Z

Zaworski

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Re: old johnson 4hp issue

sutor623 said:
Here bud, check this out. I had the same issue. Never ended up drilling the holes any better, but pulled the powerhead and cylinder head and cleaned all the passages. I had a blockage preventing water from getting around the bottom cylinder. http://forums.iboats.com/johnson-evinrude-outboards/coolant-passage-issues-532341.html
Click to expand...

Wow...thanks for that...,im wondering if im having similar issues..im going to work on that little motor in the next day ot two and ill post my findings...
 
sutor623

sutor623

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Re: old johnson 4hp issue

Check the paint. If you can see red primer (as in my photos) then you have a hot bottom cylinder. I think I spend less than $100 and did all powerhead gaskets, plugs, carb and waterpump.
 
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