4 HP 1972 Yachtwin - Stalls After 15 min

[DIY1111]

Been nurturing this motor for 20 years ! Usually runs great. Starts right up. Used very infrequently. Read about this stalling issue... here’s where I at:

plugs new,
impeller/ housing new
run in saltwater or testing in a large pail of fresh water
exhaust water from ‘8 holes’ is hot but never changes temp
paint on cylinder has always shown overheated
haven't checked coil, points or condenser in 20 years
when stalling, squeezing primer has no effect
After stall, will not start for 5-10 minutes, then she’ll start, run and die within 10-15 minutes.

note: I did run through some shallow sand water kicking up a lot of sand while running. Intake screen looks fine.

Where should I start ? I plan to pull lower and Ck impeller.

Thx...

 

[oldboat1]

I would do it all. Rebuild the magneto. Replace the impeller (sand destroys them). Johnson maroon primer was used, so maybe that is what you are seeing, but symptoms sound like overheating (perhaps ignition parts breaking down). Carefully remove the head cover, and scrape out the water passages around the cylinders (sand or salt blockages).

 

[hardwater fisherman]

Sounds like time to pull the flywheel.

 

[racerone]

Test run with another tank and hose.----Take fuel pump apart for inspection and a new diaphragm.

 

[TN-25]

Sounds like a classic case of coil failure. It heats up then fails. Difficult to diagnose on a bench. I agree with others, time for a tune-up!

Those are sweet little motors.

 

[DIY1111]

Would like to rebuild fuel pump - where can I purchase a diaphram kit ?

 

[matt167]

Iboats. but you can pull the pumps apart easy and check to see if it's needed. I have a '82 johnny 4 which is very close to the same as yours. Sounds like fuel or coils to me.. Points, coils, plug wires and a fuel pump kit probably will not run more than $100.. Do all of that as the fuel pump kit will be a few bucks and everything else requires the flywheel removed so do it all at the same time.

 

[DIY1111]

I ran it yesterday - stalled after 12 minutes. I was squeezing the fuel primer but did slack on it for a few minutes. As she was stalling, I squeezed and could hear fuel bubbling into the carb area - she still stalled. I immediately tried to restart with no choke. Once I choked, squeezed primer - she coughed and stalled. Removed choke and she started right up and ran again - which makes me think its a fuel thing - I could be wrong .

I'm going to start systematically;

1st change the fuel tank, hose and primer ( I have a spare, newer one ). Do you think having an 8' fuel line, all 'uphill ' ( about a 2' lift ), fighting gravity matters ?

At the same time, I will pull the fuel pump apart and inspect ( I hear pulling these apart and reassembling is tricky ) How will I know if the diaphragms are serviceable ?

Lastly, if the above does not remedy the problem, I'll pull the flywheel and replace points, coil, etc.
Is there a way to test the coils ?

Lastly, I would like to pull the cylinder head off and inspect that area too.

 

[Vic.S]

Thoughts... but not necessarily in any logical order

Are you sure the tank vent is open and clear ... try taking the cap off

If you have a spare tank, hose and primer bulb try it .... Raise the tank to see if it helps

If you can hear fuel entering the carb bowl when you squeeze the bulb it is obviously not full .. This points to a fuel delivery problem. Poor pump, air leaking in, restriction ??? All should be overcome / confirmed by pumping the bulb continuously

See Leeroy's ramblings for some advice on pulling the fuel pump apart ........ If you let it all fly apart without carefully noting how its all put together it will take you ever to figure it out
https://www.leeroysramblings.com/Out...0articles.html

Do some diagnostic testing before pulling the flywheel ( make sure you have the correct type of puller and know the correct torque for the retaining nut) If you pull it you may not be able to identify a problem unless you see two manky coils

Check the sparks A couple of in line spark testers would let you watch what was happening sparkwise

It's a points ignition system I believe with two sets of points and two coils......... Its difficult to believe that both coils would fail at the same time ..... You'd expect one to fail first and the motor to carry on running on one cylinder ... that does not seem to be happening

 

[DIY1111]

OK. I like the train of the thought. I will check on the fuel delivery 1st, and go from there.
Stay tuned.

 

[Crosbyman]

my money is on coils and condensers

 

[DIY1111]

Stay tuned...

 

[DIY1111]

I had a spare fuel pump that I bought years ago for this exact reason. I put it on and - boom! all is good again. The primer stayed rock hard... ran great - no stall.

I took apart my fuel pump and a few parts did slide out of place. I have them all. Not sure of where a few go ( I did save the positioning of everything ). The (2) diaphragms look tired - very worn looking.

I’d like to rebuild it - need a kit...

And, is there a clear diagram of the assembly ?

 

[merkdawg0084]

The fuel pumps aren’t too hard to rebuild, but it’s just as cheap almost to buy a new one on eBay, If you do rebuild the pump, Take pictures with your phone, pay close attention to how the pump is oriented on your motor. LeeRoy’s rambling is a great site and you tube has a few good videos.,

 

[Crosbyman]

info ...

http://www.leeroysramblings.com/Rebuilding_fuelpump.htm


scribe the outside of one side....with a felt pen or scribing tool to know which side must align...when assembling


read the instructions a few times.


i put crazy glut on he spring bases and domes to secure them in place otherwise they fly away to tip over upon reassembly

p.s. primer bulb should not be rock hard..... should be soft and pliable even after filling the carb... the pump will do the rest of the work

 

[Crosbyman]

btw... fuel pumps are 20$ ...from China and some have cut some diaphragms from nitril gloves.


finish the pump rebuild with a blow test air passes in to out NO air passes OUT to IN

 

[DIY1111]

Holy Cr*p ! I read those fuel pump reassembly directions - they are intense ! After reading it, I do believe that my 'old' fuel pump that I just replaced, and has been working for quite some time, was probably rebuilt, pre-me -- incorrectly. I took pix before I removed from the engine and the tabs that are supposed to be "up" were not and the drains were not "down".

I do have one 'extra' part that I do not see in the reassembly pix. It looks like a welch plug, maybe a 1/4" in diameter - not sure where its home is. Its not the spring support. Any ideas ?

I do want to rebuild this 'lil thing just for fun... I'm in search of a rebuild kit.... China ? Nitrile gloves ? Yuck !

 

[oldboat1]

goes on top of a spring, where the spring contacts the diaphragm. I have a couple of the cheap ones and the one I've installed is still working fine. Nitrile glove material must work. If in doubt, buy an oem pump ($$), or a Sierra pump. I've had poor luck with rebuilding, but others have no issues. I think it's the size of your thumbs or something. Patience, maybe?

 

[DIY1111]

On top of the spring ? Its not the dome support ( that tiny thing ) and its not the thing that sits under the spring - it something else...

 

[Crosbyman]

instruction sheets shows where part go (plastic domes) ... after a few rebuilds you wil be fine I have had $20 chineese pumps working for a few years now. oem pumps cost 2 arms 3 legs