Rebuilding 1956 Johnson 15hp FDE-10

[chippster]

Last weekend I purchased a 1956 Johnson 15hp electric start outboard. It has not been run for 20-ish years according to the previous owner. He said that he got it from an old neighbor and hadn't ever run it. It was in his workshop and looks to have been kept inside all this time. No electric switches came along with it.

First thing is to compression test it and check for abuse to flywheel, as advised on several other threads. It does thunk-thunk when the start lanyard is pulled, so I'm hopeful that it has good compression. I do wonder about it having no oil for so long, and air bypassing the rings. And conversely I'm concerned about spraying oil into it and skewing the results by having too good of a coating of oil. Also, an auto mechanic mentioned today that the rings could be stuck to the pistons and so not expand and conform to the cylinder as the pistons travel up and down. Any thoughts out there on the best procedure for checking the compression? I was planning on doing the compression test "dry" first.

Another concern is that the prop can be wiggled a bit, maybe 1/8" or so - it feels a little loose. Should the prop be essentially tight on its drive shaft? What needs to be done if it is unacceptably loose? I didn't find a satisfying answer in old threads on the subject.

Given that the compression is good and that the prop is OK or can be fixed, the work schedule would be:

* Replace points, condensers, sparkplugs and wires, and probably coils.
* Add Fuel pump - the way described on this site
* Fill lower gears with white-grease per advice from duckworks site.
* Make a diy12v circuit for starter only (electric starter assembly is intact and mounted on engine). Schematics to do this are available. Don't need the electric choke feature.

Also, thanks to dh4winn79 for his outboard motor stand plans.

 

[1946Zephyr]

Re: Rebuilding 1956 Johnson 15hp FDE-10

I would get some oil circulated in the engine first, before you start cranking on it. Getting those parts lubbed up first, is the best way to prevent any dammage.

 

[lindy46]

Re: Rebuilding 1956 Johnson 15hp FDE-10

Yes, definitely lube the cylinders before doing a compression check. Compression should be around 100psi and even on both cylinders. The lower unit needs 90wt. marine gear oil, NOT white grease. Prop should be fairly tight on the shaft. Is it moving in and out 1/8"? You will get movement of the entire prop assembly if you try and turn the prop when the motor is in gear. It will turn about 1/4 turn, and that is normal. I'd check to make sure the drive pin and cotter pin are in place, and that the nut is tightened properly. Does the motor have the starter solenoid junction box? If not, you can purchase a used 12 volt starter solenoid and mount it right under the hood and use a pushbutton start at the motor. Fairly easy to wire that way if you're not planning on using a remote starter switch.

 

[HighTrim]

Re: Rebuilding 1956 Johnson 15hp FDE-10

Yeah leave the grease for the older non shift motors.

Just an FYI as well, you likely know, but you cannot use an auto solenoid, you need a marine one.

 

[ultra353]

Re: Rebuilding 1956 Johnson 15hp FDE-10

20:1 oil ratio on that motor as well

 

[chippster]

Re: Rebuilding 1956 Johnson 15hp FDE-10

* Re-read Max W's article on duckworks and saw that he was only recommending white grease in situations where the goal is to extend the life of a shifter lower unit that's on its last lap. So, will service normally with oil.

* Will lube the engine properly and then compression test.

* Propeller retaining nut is loose - moves with fingers. So tightening it should do the trick.

* Like the button switch suggestion and will implement it. Should make for a clean install.

* Noted on the oil/gas ratio.

 

[kfa4303]

Re: Rebuilding 1956 Johnson 15hp FDE-10

This link may help too.

Maintaining Johnson E & FD Serie

 

[chippster]

Re: Rebuilding 1956 Johnson 15hp FDE-10

Planning on doing the compression test this weekend and wanted a little more advice on the how-to: if the cylinders are lubed with an oil spray through the sparkplug hole, the wrist pins and main bearings are still dry. Since the engine hasn't been run for 20+ years so it's probably bone dry inside the crankcase. Any ideas about how I could inject or spray some oil into the crankcase before I do the compression test?

And, where I'm going to do the test is at about 7300 ft elevation. So I might need to adjust the compression readings to take the less dense air into account. I found the following table from another forum. Not sure if it's accurate, though. Chime in if you have more info or can verify this chart.

Compression Test Altitude Compensation Factors
Altitude Factor
500 0.987
1500 0.960
2500 0.933
3500 0.907
4500 0.880
5500 0.853
6500 0.826
7500 0.800
8500 0.773

 

[HighTrim]

Re: Rebuilding 1956 Johnson 15hp FDE-10

On my motors that I store I spray fogging oil through the carb onto the reeds while pulling it over. The negative pressure will suck the oil through the reeds into the powerhead.

You may be overthinking it though with the compression adjustments. You want the cylinders to be withiin 10 percent of each other. You will know if there is a problem.

 

[steelespike]

Re: Rebuilding 1956 Johnson 15hp FDE-10

If compression turns out low,under 100 psi A decarb treatment with something like Sea Foam has shown good result freeing up rings and clearing carbon.
Service manuals indicate 24:1 Use TCW3 rated oil.

 

[64osby]

Re: Rebuilding 1956 Johnson 15hp FDE-10

That's a great looking motor, I'm sure with a little work testing and replacing the consumable parts you will have a motor as good as new.

I have several of that vintage that are fantastic runners. There are others here that have many many more than I do and they offer very sound advice.

Good luck with her and :welcome: to iboats.

 

[chippster]

Re: Rebuilding 1956 Johnson 15hp FDE-10

I'll spray fogging oil through the carburetor. Plus the starter lanyard will only get pulled a few times and slowly at that, so the engine shouldn't get too much wear and tear. Also, thanks for the steer on Sea Foam - I'll give it this treatment regardless of the compression readings. And, thanks for the welcome to iboats!

 

[chippster]

Re: Rebuilding 1956 Johnson 15hp FDE-10

Went to auto parts store and rented (free) their compression tester. Before leaving to pickup tester, I'd sprayed some Liquid Wrench into the cylinders. Upon return I put some oil in the cylinders. With the tester, the cylinders came up to 72 and 68 psi. Taking into account the elevation at my house , 7400 feet, that would put the cylinders at approximately 90psi top cylinder and 85psi bottom cylinder respectively, using the adjustments from my earlier post. There a several sources that list the identical altitude compensation table so based on that, it looks like my engine is a go!

 

[nwcove]

Re: Rebuilding 1956 Johnson 15hp FDE-10

id be ok with those comp #'s at sea level.

 

[chippster]

Re: Rebuilding 1956 Johnson 15hp FDE-10

85psi and 90psi aren't exactly spectacular but I have read a post or two where people wrote that they'd accept 80psi and over. Good to get a note that these numbers would be ok at sea level. I should have posed this as a question rather than writing that this engine is a "go".