1955 Johnson 25hp

[SumDumGuy]

removal of power head bolts

removal of power head bolts

Removed the manual and electric starters today. Also removed the carb.

I started to pull the bolts for the power head, but I have 2 that are incredibly stubborn. I have tried several applications of PB with no effect (it did work well in helping the others get out). I have tried heating the bolts, too. Basically I have been going in circles with the PB and heat.

Any other ideas for getting the bolts to move? I am concerned that I will be destroying the bolt slot soon, and I am not going to pay 5 bucks a bolt to replace them.

 

[F_R]

Re: 1955 Johnson 25hp

Are you using a hand impact screwdriver? The kind that rotates the bit when you whack it with a hammer. The hammer blow keeps the bit in the slot and it will either come out or twist off. Either way, by golly it is going to turn. An outboard mechanic can't live without one of those.

 

[SumDumGuy]

Re: 1955 Johnson 25hp

I am not using one of those, but I am about to go out the door and get one.

Looking at my previous posts it would be painfully obvious I am nowhere even close to being any type of mechanic.

 

[SumDumGuy]

Re: 1955 Johnson 25hp

F_R,
Once again great advice, thanks!

6 bucks, harbor freight, one bent bit and the head is now off.

moving forward...

 

[HighTrim]

Re: 1955 Johnson 25hp

I have to agree with Frank here, I have no idea what I would do without mine.

 

[SumDumGuy]

Re: 1955 Johnson 25hp

I am currently waiting on a couple parts to really move forward. In the mean time I have stripped most of the disgusting paint of the motor and will probably install the gear selector today.

Quick question...
According to the parts diagram there should be a shock absorber between the powerhead and the lower assembly. This motor did not have one when the head was removed. Is it critical to have one installed?

 

[SumDumGuy]

couple more questions...

couple more questions...

Can I bore and tap at one of the marked locations for a fuel pump?

Also, any issues removing the mercury switch on the throttle arm?

How about the pressure cut-out? What does it do anyway? If I get too much pressure the spark is stopped?

I would guess that both switches are simply safety interlocks and that the motor can/will run without them?

Thanks!

 

[HighTrim]

Re: 1955 Johnson 25hp

Well I have to ask, why would you want to remove the safety features?

You could bypass them, but I would not recommend it. They rarely fail.

The mercury switch ensures you do not start at a high throttle setting, the vacuum cut out grounds a cylinder when excess vacuum is created in the intake manifold due a runaway condition caused by a broken shear pin for example.

 

[Woodstock60]

Re: 1955 Johnson 25hp

I have two of these exact motors, one I restored, dissecting piece by piece, stripping, cleaning, painting and repairing the other for parts, and I do have some spare parts if you get stuck. I will tell you a few things about it that I know first hand. First, you need the starter, you will never start it cold by hand, once she's warm the pull starter will do it in a pinch, second, this motor is louder than anything you've heard on the water, wide open it sounds like a cigarette boat. third, it says 25 hp but it has the power of a thirty five, maybe forty! and lastly it has no fuel pump, I added my own aftermarket. The motor is good and the compression will be ok as long as the cyl. are even or darn close. Just want you to know what your getting before you put too much time and effort. Ronnie

 

[Woodstock60]

Re: 1955 Johnson 25hp

The mercury switch ensures you do not start at a high throttle setting, the vacuum cut out grounds a cylinder when excess vacuum is created in the intake manifold due a runaway condition caused by a broken shear pin for example.[/QUOTE]

Do you know what cyl. it cuts out? And how could you bypass ( for testing purposes)

 

[HighTrim]

Re: 1955 Johnson 25hp

Usually the bottom, but whatever set of points the lead runs to. I think I have personally only had 1 bad one though out of the hundreds of 50s omcs I have.

 

[SumDumGuy]

Re: 1955 Johnson 25hp

Chris -
Why remove safety features? Good question, no real good answer. I do not have the control box for the motor so there is nothing that needs to be hooked up for the motor to function. The original "control" cable with the motor is fubar and will need to be replaced.
Most likely I will only run cables for the starter motor and perhaps the choke (dunno yet, not quite sure what I am going to do with this thing).

I am not real worried about the mercury switch but the cutout switch seems to be a pretty good idea. The issue I have with the cutout switch is when I got the motor it was dangling by way of the pressure tube and the cutout wire. I see it is shown on the parts diagram with the carburetor group. Can you tell me where it is mounted?
I would guess the red arrow is the mount bolt and ground location (???). How about the green arrow? Is that orifice there to allow the air a place to go when the diaphragm deflects?

Ronnie -
That's some good info and thanks for the parts offer. I'm especially interested in the power performance mentioned, but not so much the noise.

I am guessing that you added a pulse type fuel pump? Where did you tap for the pulse?

----------
I am currently doing a couple of little things here and there with this motor while waiting on a carb kit. The place I ordered seems to be a bit strange. I placed an order for a power head gasket one day, the next day I ordered the carb kit. Finally got the gasket, but the carb kit status is still listed as processing (2 weeks later). Previous carb kit purchase I made here and got it within an expected time frame. Guess that is what I deserve for trying to save a couple of dollars. :blue:

 

[F_R]

Re: 1955 Johnson 25hp

The red bolt is the mounting bolt. It mounts to the port side bracket, between the bracket and carburetor. I suppose the green arrow does allow atmospheric pressure to the inactive side of the diaphragm.....as far as I know. Now that unit is so simple, it is a wonder that nobody understands it....but few do. Intake vacuum pulls the diaphragm against a large coil spring. When it pulls hard enough, the metal center of the diaphragm contacts the center terminal bolt of the switch, electrically connecting that terminal to the spring, then through the spring to ground. That shorts out one set of points, killing the spark to that cylinder until the engine slows down and vacuum goes back to a normal level. The vacuum switch cannot do anything unless vacuum is applied, so it will NOT cause a no-spark condition on a non-running motor.

So why is it even necessary to be there? Because that engine will run wild without it if it is over revved in a no-load condition. That can happen even when starting it in neutral. And since there is no ignition switch, there is no way of turning it "off" manually, so it just keeps on revving. Even pulling the choke won't stop it. In fact it often makes it worse because the choke also opens the throttle shaft, inviting even faster revving. If you have ever experienced it, you know it is a hair-raising fright.

You answered your own question on the fuel pump pulse source. Use one of the holes you circled. Going in and using the tank pressure valves is the hard way and kind of foolish in my humble (or not) opinion.

 

[F_R]

Re: 1955 Johnson 25hp

Quick question...
According to the parts diagram there should be a shock absorber between the powerhead and the lower assembly. This motor did not have one when the head was removed. Is it critical to have one installed?

I can't help but wonder what shock absorber you are talking about??? Can you be more specific?

 

[SumDumGuy]

Re: 1955 Johnson 25hp

Thanks for the info F_R.

AS far as the shock absorber it is shown in the following pic. Of course I may have the confuse again....

 

[Chinewalker]

Re: 1955 Johnson 25hp

That is actually part of the starter bracket below it in the picture.

 

[SumDumGuy]

Re: 1955 Johnson 25hp

I was just cleaning and prepping that piece for some paint. Now that you say that I know exactly what your talking about.

Thanks!

If nothing else I am getting a little bit less flat out stupid since starting this project (if I can retain some of this info). Now if I can just figure out how to get that spark plug wired into the fuel can.

 

[Woodstock60]

Re: 1955 Johnson 25hp

Here are some pics of the fuel pump I put in. http://i569.photobucket.com/albums/ss133/squid12121/fuelpump1.jpg , http://i569.photobucket.com/albums/ss133/squid12121/fuelpump2.jpg , http://i569.photobucket.com/albums/ss133/squid12121/fuelpump3.jpg , http://i569.photobucket.com/albums/ss133/squid12121/1955johnny25hpbefore.jpg The last one is what I started with.

 

[SumDumGuy]

Re: 1955 Johnson 25hp

Thanks for the pics! That thing started out rather ugly, good job making it shine.

Where did you end up getting the fitting for the cover (pulse feed)?

 

[Woodstock60]

Re: 1955 Johnson 25hp

I found some brass tubing of the appropriate size and drilled out the cover so it had a tight fit and I think I jb welded it.