4 hp johnson ignition help

[deryck]

i have a 1978 4 hp johnson outboard (4w78e) ran great for the 4 or 5 times i ran it. it was recently rebuilt when i bought it. started running rough when going from full speed to lower speed then stalled and would not even slightly fire again. there is no spark now, i did replace spark plugs and still nothing. checked all connections and coils look brand new. the only thing i can see that is worn is the sensor assembly. is there any advice or anything else that may be causing this problem? thanks in advance! also i did attempt to test the coils from spark plug wire to coils and both had the same reading.

 

[Boobie]

Go to cdlelectronics.com for trouble shooting procedures

 

[deryck]

Sanded all connections and checked for weak/broken wires. I was able to wiggle the magneto plate tightened that up but still nothing. Could it be the pick up? It looks fairly worn. Thanks for the replies i will take a look at cdelectronics.

 

[fdrgator]

There is no reason for the sensor being worn unless it has been rubbing on the flywheel magnets. So maybe that has damaged it, hard to guess. If you do replace it, make sure it is adjusted for proper clearance so it doesn't happen again.

 

[JSPG]

Hi everyone,


I'm reaching out to ask for help regarding my 1978 Johnson 4HP outboard (model 4W78E).


I used this motor regularly until around 15 years ago, when the drive pin broke during use. I stored the motor away in a shed and haven’t used it since. Unfortunately, I’ve now realized that the propeller is missing, and I’m in the process of restoring the motor.


Looking at the parts diagrams, I’m unsure which components I actually need to complete the lower unit. The prop shaft is still in place, but I don’t know if all I need is a new propeller, drive pin, and cotter pin, or if the prop requires additional bushings or inserts that need to be purchased separately.


If anyone here has experience with this specific model (4W78E), I’d really appreciate any guidance on:

• What parts come with a replacement propeller (OMC 0319004 or compatible)
• Whether any internal bushing or hardware must be installed separately
• Any photos or diagrams showing a fully assembled propeller setup on this motor

Thanks in advance for your time and help.
I’d love to get this motor running again and pass it down to my son as a family legacy project.

 

[fitz73222]

All you get is the propeller, the other parts will need to be purchased separately. you can order them right from this website.

 

[JSPG]

Thank you for your answer.

Based on what I’m seeing in the parts diagram and on the motor itself, I believe the components I’m missing are:

• The propeller (weedless style)
• The cotter pin
• The drive pin
• The propeller hub
• The propeller clutch ring

Am I correct in assuming these are all the essential parts needed to complete the propeller assembly?


Also, when I first pulled the motor out of storage, I noticed a clear plastic ring at the base where the propeller mounts. It was deformed and tangled with fishing line, and unfortunately I lost it. The odd thing is, I don’t see this ring listed anywhere in the parts diagram.


Could this have been a part that’s included with the propeller or clutch ring? Or was it perhaps not original and someone had added it as a spacer or seal?


Thanks again for helping me get this motor back together properly.


Best regards

 

[fitz73222]

Those are the parts you need as listed. I have a 1978 and 1980 4 hp weedless drive and none have a clear plastic ring.

 

[fitz73222]

Are you sure that this gearcase is original to this motor? Earlier versions back in 1970 had additional bushings and parts. Look up the parts for 1970 and see if you recognize anything.

 

[JSPG]

According to the parts diagram provided by Boats.net for my specific model (4W78E), the gearcase does appear to match what I have. That said, I’ll attach a few general photos of the motor in case you recognize anything that looks out of place or possibly missing.


I’m also including:

• A photo of the model and serial number plate
• A photo of the gearcase exactly as I found it when I pulled the motor out of storage

Unfortunately, I don’t have much background on the motor’s service history. It originally belonged to my grandfather, then was passed on to my uncle, and finally to myself about 20 years ago. At this point, I honestly don’t remember if anything was already missing back then.


Thanks again for your time and help—I really appreciate the support

 

[JSPG]

also attaching a picture of the parts diagram from the website

 

[fitz73222]

I just went out the shop and removed the propeller from the exact same 1978 4 hp weedless engine. #25 and #26 is all that is there. plus the drive pin and cotter pin. Go forth and order!

 

[JSPG]

I just went out the shop and removed the propeller from the exact same 1978 4 hp weedless engine. #25 and #26 is all that is there. plus the drive pin and cotter pin. Go forth and order!

you sir, are a legend, thank you so much

 

[JSPG]

I just went out the shop and removed the propeller from the exact same 1978 4 hp weedless engine. #25 and #26 is all that is there. plus the drive pin and cotter pin. Go forth and order!

does your 1978 4hp looks exactly like mine? also on yours the propeller has 2 or 3 blades?

 

[fitz73222]

It is identical to your engine, 1978 4 hp, 2 blade propeller, you may also want to check if there is any water or gearlube loss where that fishing line is wrapped around the propeller shaft. Fishing line can cut that seal.

 

[JSPG]

It is identical to your engine, 1978 4 hp, 2 blade propeller, you may also want to check if there is any water or gearlube loss where that fishing line is wrapped around the propeller shaft. Fishing line can cut that seal.

yes, checked the oil and it came out spotless. also starting to believe the misterious plastic washer i found could be molten fishing line.

Also, regarding the fuel pump on this motor.


I disassembled the original pump and unfortunately the gaskets tore apart during the process.
Do you recommend that I buy a brand-new replacement pump, or is there a rebuild kit available for this model?


I’d prefer to restore the original if possible, but only if it’s reliable and safe to do so.

 

[fitz73222]

Sierra P/N 17-7823 fuel pump kit.

 

[JSPG]

Sierra P/N 17-7823 fuel pump kit.

so far only been able to find P/N

18-7823​

 

[Droid]

All Sierra parts are 18-xxxx, I'm sure it was a typo.

 

[fitz73222]

All Sierra parts are 18-xxxx, I'm sure it was a typo.

You are correct...Thank you