1967 Johnson 20 hp.?

[marc67john]

I have a 1967 johnson 20hp. that when in drive it is not getting all the way up to speed. Its only going about a 1/4 of what its supposed to. I've had some problems with it. First off the seal's where bad in the lower gear case and cracked the scag over the winter. So i had is welded up so the water doesn't damage the gears. So when i put it back together the motor started jumping in and out of gear. So i adjusted the "gear shifter" where you shift from forward and neutral and reverse with the screws on it to get it to go into forward so it wouldn't jump in and out so it ( Completly engaged). Which brings me to my new problem of only going 1/4 of its speed. It starts fine and idles great. and reve's all the way in neutral when i do it with the throttle. But not in forward. Any suggestion???? model #20 R- 69B 1967 johnson 20 hp. p.s. checked the carb and it seems good.

 

[petryshyn]

Re: 1967 Johnson 20 hp.?

are you sure its hitting on both cylinders? kill one at a time and see if it still idles.

Try "pull starting" in forward as compared to in neutral....is there a noticeable difference in effort? After the work on the bottom end, it may have introduced new problems.....

 

[tashasdaddy]

Re: 1967 Johnson 20 hp.?

see the top secret file.

 

[marc67john]

Re: 1967 Johnson 20 hp.?

its seems to be hitting on both cylinders i pulled the spark plug and still idles fine. and there is a noticable difference when its in gear than in neutral. so i think theres good compression.

 

[petryshyn]

Re: 1967 Johnson 20 hp.?

is there a noticeable difference in idle when you kill one cylinder at a time?

 

[marc67john]

Re: 1967 Johnson 20 hp.?

the uppper cylinder theres a little bit in difference.

 

[petryshyn]

Re: 1967 Johnson 20 hp.?

how about the lower cylinder?

 

[marc67john]

Re: 1967 Johnson 20 hp.?

lower cylinder seems good, thats the one that has the two fuel lines connecting to the diphram that puts the fuel into the cylinders. i pulled the top blank casting on the top cylinder and pumped the ball and gas is coming out the top cylinders like its supposed to. I Don't think its a fuel problem. The mix i use is 50:1. I could try new spark plugs but it fires right up on first, second pull.

 

[F_R]

Re: 1967 Johnson 20 hp.?

how about the lower cylinder?

99% of no power problems are running on one cylinder. Usually only one and the other one is dead. If you have one strong cylinder and one weak one, look for compression problems or water getting in the weak one.

 

[marc67john]

Re: 1967 Johnson 20 hp.?

ok so i went and got a compresion tester. I pulled the top plug and put tester in and it fired up and read 100 on top cylinder. I put the plug back in and took bottom out and tried to start with tester in but it didn't start it sputtered the compression tester read 90 on bottom cylinder. anyone with a diagnosis?

 

[MushCreek]

Re: 1967 Johnson 20 hp.?

You're not supposed to start the motor while using the compression tester. The fact that it started on one cylinder, and not on the other, tells me that one cylinder isn't firing strongly. Most likely it's a bad coil. They may work at lower speeds, but they break down under load. It's very common on older OMC's.

 

[jbjennings]

Re: 1967 Johnson 20 hp.?

"I pulled the top blank casting on the top cylinder and pumped the ball and gas is coming out the top cylinder like it's supposed to."

I don't understand this quote. You shouldn't have gas coming out the top cylinder when you pump the primer bulb as far as I know. If so, I would think you had a float valve leaking and letting fuel pour out of the carb.
You also shouldn't be running the engine while doing a compression check, but either way, your results show a lack of spark to the top cylinder in my opinion. I believe you have weak spark to the top cylinder which is why it would crank when you tested the top cylinder and would NOT crank when you tested the bottom. The bottom cylinder is the only one making power. You need to get a $6 spark tester from autozone and see if the top cylinder will actually make a nice bright blue spark that will jump at least 1/4 inch gap. I believe when you test it with a tester you will find good spark on the bottom and weak spark on the top.
Good luck,
JBJ

 

[marc67john]

Re: 1967 Johnson 20 hp.?

You're not supposed to start the motor while using the compression tester. The fact that it started on one cylinder, and not on the other, tells me that one cylinder isn't firing strongly. Most likely it's a bad coil. They may work at lower speeds, but they break down under load. It's very common on older OMC's.[/QUOT

How do i get to the coils. and do you know where to find new ones. I also tested the spark plugs and both have a nice blue spark. (break down under load) that seems to be it when i run it its will only go a 1/4 of the speed when its pushing the boat.

 

[jbjennings]

Re: 1967 Johnson 20 hp.?

You pull the flywheel to get to the coils. You'll need a harmonic balancer to pull it. If you beat it off with a hammer you'll ruin it. You'll also need a torque wrench to reinstall the nut to 45 ft.-lbs. of torque.
I have to ask one question and please don't think I'm in any way being a smart-aleck because I was once in your same position and it took me a while to understand why just looking at the spark won't work, too.
Here's the question:
What did you do the spark test with? If your answer is "not with a spark tester" or "grounding the plug on the block", then you haven't done a spark test. I'm attaching a pic of a spark tester so you'll know what to look for. I got mine at autozone. It very well may be that you have good spark and there's a totally different problem, but if you haven't done a correct spark test, you might be chasing fairies for a while.
BTW, welcome to iboats! Iboats sells the coils. Just ask if you need the part number.
This may help if you have questions about changing the coils:http://forums.iboats.com/showthread.php?t=294072
GOod luck,
JBJ

 

[marc67john]

Re: 1967 Johnson 20 hp.?

what i did for the test is ground it to the block. It looked bright and blue. I think im going to try replacing the coils and since i have it apart probably the spark plug wires also. I did find where i could buy coils. I hope that changing the coils is my last fix on this motor. Thanks for the help.

 

[crxess]

Re: 1967 Johnson 20 hp.?

Points anyone? one set of points could have worn the rub block down and not be opening enough to fire properly.

Look before buying. Someone may have already replaced coils if you got it used.

 

[MushCreek]

Re: 1967 Johnson 20 hp.?

I believe you can get all of your ignition parts right here at iboats. crxess is right- make sure the rest of your ignition parts are right before replacing the coils. Usually bad coils are obvious, with cracks in the insulation.

 

[F_R]

Re: 1967 Johnson 20 hp.?

lower cylinder seems good, thats the one that has the two fuel lines connecting to the diphram that puts the fuel into the cylinders. i pulled the top blank casting on the top cylinder and pumped the ball and gas is coming out the top cylinders like its supposed to. I Don't think its a fuel problem. The mix i use is 50:1. I could try new spark plugs but it fires right up on first, second pull.

Ordinarilly, I would say you are on the right track with the spark issue. However---the above quote raises great concern about the diagnosis.

WHAT diaphragm that puts fuel into the cylinders?? And what are you talking about, gas is coming out the top cylinders?? Those statements don't make a lick of sense. Offhand I say you DO have a fuel problem (too much fuel), but I can't figure out what you are saying to us. Perhaps some pictures will help.

 

[marc67john]

Re: 1967 Johnson 20 hp.?

I'll try to explain, im new to working on my boat motor. The line from the gas tank makes the fuel connection to the motor. the line that connects it goes to what i call a "diaphram". and the other line comming off that goes to the carb. I guess this could be called a fuel filter im not sure. but it has two fuel lines connecting to it. And that "fuel filter, diaphram" connects to the cylinder ( bottom ). I hope this makes sense???? I pulled the flywheel and looked at the coils the one towards the back seems to be worn on the flat point (i.e. the part that's supposed to have little groves on it like the front one does) it seems to be worn smooth. the front coil still has the little groves on it. COULD THIS BE THE PROBLEM????? SUGGESTION???? THANKS FOR ALL THE HELP SO FAR JUST TRYING TO GET BACK ON THE WATER.

 

[samo_ott]

Re: 1967 Johnson 20 hp.?

I think he is saying he removed the fuel pump and/or the other bypass cover.

As for the coils, I'm not sure what you mean. They should not be physically worn. Can you post pictures?