Compression for 1958 Johnson Super Seahorse

[John Mashl]

I’m a brand new member.  I have two 1958 Johnson 35hp Super Seahorse outboards, one RDS-20 and one RDSL-20.  I think the RDSL has been converted to a short shaft.  I’m in Colorado.  One outboard was purchased in Colorado, the other was purchased in Indiana.  I don’t see a lot of corrosion and believe they have only been run in fresh water.  I plan on using one of these on a restored 12’ 1955 Chris Craft Barracuda kit boat.

I do not know when they last ran.  I have not attempted to start them.  My plan is to first check the compression and spark.  I have rebuild kits for the carburetor, fuel pump, ignition tune-up, gear case seal and water pump.

I checked the magnetos and they appear to create a good spark.  I checked the compression on both motors.  I used fogging oil and hand pulled the motors over about five times.  (I’m rebuilding a control box/wiring harness so I haven’t tried the electric starter yet. )

The first motor had 90 psi in both cylinders.  The second motor had 70 psi in both cylinders.

I have a Seloc manual.  Both cylinders in both motors have the same compression which is good.  The manual also says the compression should be 90-100psi for this year outboard.

I’d like to know if these outboards are worth restoring.  Are these compression numbers OK?   So far, I can’t find powerhead parts (pistons, rings etc).  If parts are available somewhere, I’d be interested in getting at least one powerhead rebuilt.

I’d appreciate any knowledge or opinions on how I should proceed.  Thanks.

John

 

 

 

[outbdnut2]

Try to get both running before considering a teardown/rebuild.   After running and warming up once, you may be surprised how much higher the compression is.  Fogging oil does not create much of a seal on the rings on a motor that hasn’t been run for a long time.  Be sure to use a compression gauge with a check-valve at the motor end of the hose.  It will read lower if the valve is only at the gauge end due to the volume of the hose.   If one or both start and run good, forget compression and enjoy it.   I’ve seen  too many people rebuild outboard motors that don’t need it due to initial compression numbers.   If one or both need rebuilding, and you find parts (they are out there), you can easily spend more than the motor will ever be worth, so it may be better to buy a motor that can be demonstrated running good; unless cost is not an object and you really enjoy the rebuilding part of the hobby for fun.  When you ran compression test, was the choke open and the throttle cracked open a bit?  You measured compression by pulling the rope.  Did you disconnect the linkage to the compression relief valves first?  If not your readings will be low.  You may find a significant compression increase using the electric starter.  Using electric start, you also don’t have to disconnect the compression relief valves to check compression, as they only are linked to the recoil starter.  You can crank it by using jumper cables – get a good connection to the starter first and then connect the cables to the battery to crank, as it’s hard to connect to the starter when the motor starts moving on its shock mounts while cranking. Your 1958 Super Sea Horses are good motors, and the first Johnsons to have fuel pumps and not need a dual line pressurized fuel tank.  They are also the first to have the “Super Quiet” leg that the 35s all had for 1959 and the 40 HPs that followed.  Ther are the last to have a metal case up top.  Did you get the wiring harnesses and the starter solenoid boxes that mount in the boat with them?  You will need those for electric start wiring in the boat- or at least one set  to put in the boat if you are just running one motor at a time on one boat.  That stuff is often left in an old boat that gets scrapped or sold.   If the solenoid in the box in the boat is bad, OEM factory and Sierra are both good replacements and available.  The solenoid looks a lot like one from an older Ford, but the Ford solenoids are wired different inside and will  not work, and in some cases will fry wires in the motor unless you understand the wiring changes needed.  Your gas/oil fuel mix is 24 to 1.  It was 1964 and later that 50 to 1 was specified.  Use ethanol-free gasoline if you can get it.

Hope they both start and work well for you.  I have nine 35 HPs from 1957-58  and  never bothered to check compression because they all run good!  I had to pull the head on one that wouldn’t pull over all the way because there was a mouse nest in one cylinder – must have crawled up the  exhaust!

Good Luck!

Dave

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John Mashl

[John Mashl]

Dave,

Thanks for the info.  I don’t think I touched the choke or throttle before checking the compression so I don’t know what position they were in.  My compression tester does have a valve on the motor end.  I didn’t disconnect the compression relief valves.  I saw them but didn’t realize what they were.  (The last time I played with old outboards I was a teenager working on mid ‘60s 18 hp Evinrudes.)

All the wiring and fuel lines appear to be connected and in fair condition.  I asked a local outboard shop about what spark plugs to run at my elevation.  (I’m at 7,000’ in Colorado.  Some mountain lakes are higher.)  I believe they said to run a little hotter plug.  He sold me some Champion J8Cs.  I also plan to lean the air/fuel mixture using the carburetor’s slow & high speed adjustments to compensate for the less dense air.

I have the starter solenoid boxes and the wiring harnesses for both motors.  The solenoids work ok.  I can get ethanol-free gas.  In the 60’s we used to call lead-free gas “white gas.”  Now it’s all lead-free.  Good tip on the 24 to 1 for the gas/oil mix.

What spark plug would you recommend?   Champion J8C?  I think one motor had J4C plugs (the Indiana motor?)

I’ll try checking the compression using the electric starter.   Then I’ll try getting them running and check the compression again.

Thanks again.

John

[TJ Brandon]

I agree with the advice above, get them running and see how they do. I have one I rebuilt and and after some fighting it’s running great. J4C are the recommended plugs. For the carb, hopefully the cork floats are in useable condition. They don’t make plastic ones for these motors and OEM are hard to find. Stay away from ethanol gas if you can.

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John Mashl

[crosbyman]

To service your oldies  this book will give you all the info you need  400+ pages     comes in white or red…

you will need to pull the FW  because good sparks means nothing if coils are all cracked like most are ….

CRACKS……picture is the wrong one  can’t discard it ??  see cracked coils

just download and store on your PC  and  print locally double sided and spring bind with plastic cover sheets    make 2 books for easy reading

best book you can buy for 20$

https://watercraftmanuals.com/outboard/johnson/manuals/johnson-302231.htm

Joining AOMCI has priviledges 🙂

1 user thanked author for this post.

John Mashl

[outbdnut2]

John Mashl wrote:

What spark plug would you recommend?   Champion J8C?  I think one motor had J4C plugs (the Indiana motor?)

The recommended spark plug was a J4J, which is now J4C.  (The C means Copper electrode).  For your elevation, a J6C would be a better, hotter plug, and the J8C hotter yet.  Which you use depends on how you use the motor.  If you are trolling or idling a lot, then the J8C will likely be best for you.  If you are running at high throttle a lot, the cooler J6C may be better.  If the plug is too cold, it will foul sooner and need cleaning more often.  If the plug is too hot, you can get pre-ignition (knock or ping) which is bad for the pistons – like hitting them with a hammer.  You can’t always hear the knock/ping in a 2-sroke outboard, so you often don’t know it’s happening.  Spark plug heat range has nothing to do with how hot or how fast the engine runs.  It is all about the temperature of the spark plug’s firing electrode tip to burn off deposits and keep it from fouling.  Unless you do a lot of idling/trolling, I’d start with J6Cs and if you start to get bad idle from fouling in a short time, and they look a bit black and sooty, then go to the J8Cs.

Dave

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John Mashl

[outbdnut2]

TJ Brandon wrote:

They don’t make plastic ones for these motors and OEM are hard to find.

Over at one of the AOMCI facebook sites, there have been recent posts from a guy who has managed to 3-D print plastic floats.  He has been through several iterations and now has floats that he says work well.  I don’t know if he is set up to sell them yet, and don’t know if he follows this forum.

Dave

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John Mashl

[labrador-guy]

Hello John and welcome!   Plenty of smart people here to answer your questions.  I built two 35 Evinrudes last summer and fall.  One runs good the other has not made it to the test tank yet.  You can check out my shade tree mechanic or “boat house mechanic”  as one member likes to say, in the Current Projects Tread for members only.  I learned to ski behind one of those old Johnson’s a long time ago.  Lots of parts for these motors on ebay.  Check this member out if you want new stuff.  eddelliott@cox.net

I had two uncles that had CrisCraft kit boats way back when!   One had a brand new ’57  18 Johnson the other had a 25 Wizard.  Brings back many memories for sure.

have some fun

dale

Get’em wet…..don’t let’em set!

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John Mashl

[Sam M.]

Sounds to me like you’re on the right track!  Carburetor and fuel system cleaning, new water pump impeller, and new marine/outboard-specific gear oil are good to do before running.  Your other rebuild parts are good ones to change as well, but they shouldn’t need attention before a test run.

Speaking of testing, when running the motor in a barrel (or on the boat), make sure the water level is higher than the water pump impeller.  Normally, this means an inch or two above the top of lower unit.  The reason is, the water pump may or may not self prime (suck the water up to itself), and if it doesn’t, the impeller could quickly wear away or heat up and melt, meaning bye bye cooling system.  By having the impeller submerged, it will be automatically primed.  When on the boat, you might notice that the motor will be slightly higher out of the water when on plane, compared to at idle.  This is normal and ok as the pump is already primed, assuming the motor is still pumping water.

Another thing, if you decide to look at the ignition system with the flywheel off, there should be a felt piece rubbing on a cam around the crankshaft.  It is a good idea to oil the piece of felt so the cam and the part of the points the cam pushes on gets lubricated.

When putting the flywheel back on, the nut MUST be torqued to proper specifications for safety reasons, and to prevent motor damage.  You don’t want the flywheel to fly off!

Also, while I’m not familiar with the boat you mentioned, 35hp seems like a lot for a 12 ft boat, so you might want to double check the manufacturer’s original suggested hp.

If you’re going to run the motors with used fuel tanks, they might have debris sitting in the bottom that should be cleaned out.

One last tip: when fueling up, keep in mind more oil in the gas is safer for the motors than less.

Finally,

HAVE FUN!!!

[outboardnut]

Arthur Simler on Facebook is printing floats

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John Mashl, Phil Budne

[Author]

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