1957 Johnson 35 comp test

[Oregon Jon]

No reply from the last posts on the original thread, so here is part 2:

In the previous thread I mentioned that I was unable to get much of a reading from the compression tester that I am borrowing. I am almost certain that its either a guage issue or something I am doing wrong. I can't get a real good pull on the motor because of its location. Is there a way to test the guage? Do I need to hook up the electric start to get an accurate reading?

Also if anyone did read the last post in the previous thread I mentioned that I was afraid I had screwed something up by hooking up the starter incorrectly, but I think I am OK as I checked for spark and was good on both plugs.

As always the expert help is greatly appreciated.

 

[samo_ott]

Re: 1957 Johnson 35 comp test

I would use the electric starter to test the comp. I have the same '57 35hp engine. Pull both spark plugs out and screw the gauge fully into one hole. The engine should be braced to stop possible injury. Then to jump start the starter I would hook the positive from the battery to the side positive terminal on starter, then hook the negative to the battery and then the other end to the frame of the engine, it will spark when you make the last connection so you want it not by the battery and not on the starter. Then spin the engine for say 5 seconds... that should get a good reading Purists might say to have the water pump under water so as not to run it dry but I believe 5 secs is ok. This should give a good reading. Then do it for the other cylinder and post your results back here.

 

[tashasdaddy]

Re: 1957 Johnson 35 comp test

totally agree

 

[wbeaton]

Re: 1957 Johnson 35 comp test

Everything is fine. Take samo's advice.

 

[HighTrim]

Re: 1957 Johnson 35 comp test

Agree with Samo, yet have always hooked ground up first to prevent damage, is this procedure incorrect?

 

[F_R]

Re: 1957 Johnson 35 comp test

In the case given, electrically it really doesn't matter which is hooked up first. The way suggested above is better for a couple of other reasons though.
1. It prevents sparking near the battery. (batteries can explode)
2. Arcing to the copper terminal on the starter will cause severe damage to the terminal. Better any arcing should occur at a heavy metal bolt or something on the powerhead.

All bets are off if we were talking about a more modern motor with electronic ignition and alternators.

 

[HighTrim]

Re: 1957 Johnson 35 comp test

thank you FR, did not want to damage anything in the future, didnt mean to hijack a thread in any way. I was probably taught the way I was because it was on newer style motors, but I assume a remote starter would be ideal in this situation correct?

 

[samo_ott]

Re: 1957 Johnson 35 comp test

A remote starter would be perfect here.

 

[tmcalavy]

Re: 1957 Johnson 35 comp test

Hey TD is there a compression release on the 57 35 hp Johnsons? I think the 59's had one, to make it a little easier starting with the recoil/pull starter.

 

[samo_ott]

Re: 1957 Johnson 35 comp test

Yes, my '57 has a comp relief. I think they went from about '57-'60 (or '61)...

 

[Oregon Jon]

Re: 1957 Johnson 35 comp test

The Results are in:

Top Cylinder: 150 + psi

Bottom Cylinder 75 psi

Not exactly what I'd hoped for. What next guys?

Also, I seem to have stripped out the top plug threads, but I can still get a plug to seat if I'm careful.

By the way, compression relief has been removed from this motor.

 

[samo_ott]

Re: 1957 Johnson 35 comp test

whoah... that's a huge difference... a decarb or a head gasket are the cheap fixes... after that it gets expensive...

 

[Oregon Jon]

Re: 1957 Johnson 35 comp test

Walk me through a decarb on this motor. It is definitely different looking than my '71 'Rudes. With them I more of less cleaned them with a straightened out paper clip and there was a huge improvement.

 

[samo_ott]

Re: 1957 Johnson 35 comp test

This was previously posted by Tashasdaddy:

the way i decarb those engines: by a can of seafoam, in the tank, 3/4 gallon of premixed gas/oil, 3/4 can of seafoam. the rest of the seafoam goes in a spray of squeeze bottle. remove the air silencer from the carbs, start engine, make sure you have good water source, run engine until it get to operating temperture, kill engine, remove plugs, and put a liberal amount of seafoam directly in to cylinders, let sit for 15 minutes. now restart, ( it's going to smoke) let it the engine settle down, now spray seafoam directly into the carbs, until the engine almost stalls. keep this up until out of seafoam or the engine, quits smoking. you can just add regular premix to the rest in the tank. also changed the plugs afterwards, you will be amazed at what the water looks like when finished. wash lower unit.

Of course this assumes you can get the engine running...

 

[Oregon Jon]

Re: 1957 Johnson 35 comp test

Okay, I would assume that I should replace the impeller before I do this, or at least take a look at it. How do I do that? You wouldn't have a couple of pages from a repair manual you'd want to send me would you?

 

[F_R]

Re: 1957 Johnson 35 comp test

Oregon, I scanned through the posts pretty quickly, but didn't see anywhere that the motor runs at all. Does it?? It has to be running to do a decarb as described. Frankly, I doubt a decarb is going to fix this one. But it won't hurt to try, I guess.....maybe

Don't bother doing the water pump till you find out if the motor will start and run. If it does start and run, and IF it pumps water go ahead and try the decarb. If the decarb does any good, then you can go ahead and replace the water pump for security sake. Just hate to see you buy a water pump for a dead horse.

Backing up a bit, that plug will probably blow out. Sooner or later you are going to have to deal with that. It might be wise to go ahead and pull the head now. Then you can see inside and get a better picture of why your compression is so low. With the head off, you can take it to an automotive machine shop and have them put a heli-coil in the hole.

 

[samo_ott]

Re: 1957 Johnson 35 comp test

Or find a used head...

 

[Oregon Jon]

Re: 1957 Johnson 35 comp test

Should I take care of the head issue before I try to get it to run?

Also, I have two pressure tanks that came with my motors but both had old gas in them, or at least it used to be gas. Do I need to / can I pull of the hardware to check for rust?

And is the mix on these older models 24:1?

 

[wbeaton]

Re: 1957 Johnson 35 comp test

The mix is 24:1. At some point someone is going to say that you can use 50:1, but its not me.

Properly dispose of the old gas and then look for rust in the tanks. Don't dismantle them if they are working fine unless you want to restore them.

With your compression I think a decarb is wishful thinking, but if you can get it running I guess it can't hurt. I'd pop that head and have it helicoiled or find a donor (could be cheaper). You need to see what it looks like in there. I'd rather have the threads repaired before I tried to run it, but if you think you can still get a good seat with the plug then give it a whirl.

 

[Oregon Jon]

Re: 1957 Johnson 35 comp test

Anything I should know before I pull the head?

I notice that there are separate additional plates attached to the head above each cylinder. I assume this is to accomodate the pressure relief valves. I wonder, could the lower relief valve be sticking? How would I check?