1975 15 hp johnson leaking gas on its side

[Johnson209]

Hey there guys I have a leak in my motor. I found the leak when I was rebuilding my carb. Its spitting out gas and oil on its side on the top bolt, heres a pics of the motor where its leaking from to give you guys a clear picture.The motor starts up and runs fine at full throttle but dies when Its in idle. So What am I looking at, do I need a new gasket? If so, what gasket am I looking for? I tried looking at a diagram at marineEngine and I didnt see any. How do I go about tackling that leak? Does the flywheel and power head need to come off? Please let me know guys, any help, suggestion would be greatly appreciated.

thanks for viewing and have a great day

 

[RogersJetboat454]

Re: 1975 15 hp johnson leaking gas on its side

The arrows you have are pointing to the crankcase halves. The two halves put together form the main bearing journals. There is no gasket for this so-to-speak. They are usually sealed with a liquid gasket sealer, such as 3M 847.

You could try checking to see if the bolts in that area have loosened up, but don't crank them down. Most likely will need to pull the powerhead apart, and do a re-seal. Would be a good opportunity to replace other seals, an check the condition of the bearings.

 

[Johnson209]

Re: 1975 15 hp johnson leaking gas on its side

thks Roger, I appreciated your help. OK, so if the crankcase half doesnt need a gasket, I was thinking about JB welding the bolt and side where its leaking from. Do you think that would do the trick? If not how do I take off the head on this motor?

 

[RogersJetboat454]

Re: 1975 15 hp johnson leaking gas on its side

Anything you do other than pulling it apart and sealing it up correctly will be a stop-gap (no pun intended) repair. It may last 20 minutes, or it may last years.

Trying to remove all the fuel/oil from the affected area in order to allow the JB weld to get a good hold will be difficult, and if it doesn't work out, you will then have to clean away the JB weld when it comes apart.

To pull the powerhead, you will need to disconnect the fuel lines, any electrical bits tying it to the cowl, any linkages to the carb, etc. Then you would remove the bolts that hold he powerhead to to mid section. If you are going to do this, you NEED to get your self a FACTORY service manual. It will provide you with all the knowledge you need to pull off this project, and others in the future.

Notice I say FACTORY manual too, one made specifically by OMC, or BRP for this year/model motor. All the other manuals out there (such as Seloc, Clymer, etc) can get you into trouble. They try to cover a broad range of engines with one book. Their procedural and technical information can be vague, lacking, or just down right incorrect. The price for them is a bit high, you can get a fresh copy here; 1975 Johnson Outboard Service Manual 506846 - Ken Cook Co. - iboats OR.. you could keep an eye on eBay as used examples come up from time-to-time.

 

[Johnson209]

Re: 1975 15 hp johnson leaking gas on its side

Anything you do other than pulling it apart and sealing it up correctly will be a stop-gap (no pun intended) repair. It may last 20 minutes, or it may last years.

Trying to remove all the fuel/oil from the affected area in order to allow the JB weld to get a good hold will be difficult, and if it doesn't work out, you will then have to clean away the JB weld when it comes apart.

To pull the powerhead, you will need to disconnect the fuel lines, any electrical bits tying it to the cowl, any linkages to the carb, etc. Then you would remove the bolts that hold he powerhead to to mid section. If you are going to do this, you NEED to get your self a FACTORY service manual. It will provide you with all the knowledge you need to pull off this project, and others in the future.

Notice I say FACTORY manual too, one made specifically by OMC, or BRP for this year/model motor. All the other manuals out there (such as Seloc, Clymer, etc) can get you into trouble. They try to cover a broad range of engines with one book. Their procedural and technical information can be vague, lacking, or just down right incorrect. The price for them is a bit high, you can get a fresh copy here; 1975 Johnson Outboard Service Manual 506846 - Ken Cook Co. - iboats OR.. you could keep an eye on eBay as used examples come up from time-to-time.

Thanks again for the quick reply And for the service manual web sight. I order a manual for my mercury like u said from a web site n it had 5 different models and hardly pertain to my motor. The jb weld is a quick n easy solution but like you said might not hold up. I just don't want to take the fly wheel off. If it wasn't for that I'll take the head off and reseal the jacket covers with 3m. I'll see which way I may take. I like to get my job done right the first time, so maybe jb weld ain't a good idea.
Thks a bunch

 

[RogersJetboat454]

Re: 1975 15 hp johnson leaking gas on its side

I just don't want to take the fly wheel off.

How come?
The flywheel is a piece of cake with the right tools. A simple, and cheap harmonic balancer puller with grade 8 bolts will get her off. Then you simply drop her back on and torque the flywheel nut down to the correct spec.

On your motor, pulling the flywheel is considered routine maintenance. You have a breaker-point ignition. The points, capacitors, and coils should be routinely checked when you service the motor. Got to pull the flywheel to do that correctly..

 

[OptsyEagle]

Re: 1975 15 hp johnson leaking gas on its side

I can't say for sure, but aren't the arrows pointing to the leaf plate to intake manifold and not the crankcase halves. Perhaps he just has a leak in his leaf plate gasket. Since this would create a situation similar to a leaf that doesn't close on the down stroke, it would then shoot gas out this leak and certainly make the idle not so good.

 

[RogersJetboat454]

Re: 1975 15 hp johnson leaking gas on its side

I can't say for sure, but aren't the arrows pointing to the leaf plate to intake manifold and not the crankcase halves. Perhaps he just has a leak in his leaf plate gasket. Since this would create a situation similar to a leaf that doesn't close on the down stroke, it would then shoot gas out this leak and certainly make the idle not so good.

The seam the arrows are pointing to are right in the center line of the crank. That's where the crankcase halves meet to form the mains.

 

[OptsyEagle]

Re: 1975 15 hp johnson leaking gas on its side

Yeah, I think you are right. It's tough when I can't move my eyes 360 degrees around the motor.

 

[Johnson209]

Re: 1975 15 hp johnson leaking gas on its side

How come?
The flywheel is a piece of cake with the right tools. A simple, and cheap harmonic balancer puller with grade 8 bolts will get her off. Then you simply drop her back on and torque the flywheel nut down to the correct spec.

On your motor, pulling the flywheel is considered routine maintenance. You have a breaker-point ignition. The points, capacitors, and coils should be routinely checked when you service the motor. Got to pull the flywheel to do that correctly..

I don't have the fly wheel puller, hate going to the store n rent one and returning it. N the flywheel nut is hard it can be, I usually use a impact gun to get it off.

 

[Johnson209]

Re: 1975 15 hp johnson leaking gas on its side

Yeah, I think you are right. It's tough when I can't move my eyes 360 degrees around the motor.

Hey OpstyEagle , how u been. You help me out on last post with my points n condensors. hope All is good with you. Yea the leak is coming from the back of the bolt and the line where the crankcase connects. I forgot to mention I did lost a carb straw while spraying carb fluid in my spark plug holes. I think I got pretty much of it out.

 

[nwcove]

Re: 1975 15 hp johnson leaking gas on its side

the puller is a cheap tool....you can get one , and the grade 8 bolts ( the bolts that come with the cheap pullers...are just that ..cheap...dont use them!), for about $20 you can have a new tool in the tool box.

 

[dazk14]

Re: 1975 15 hp johnson leaking gas on its side

Have you tried tightening the bolt? Tearing that motor down isn't remotely cost effective and if pulling the flywheel seems like a headache, you won't like the process and expense.

Are you sure it's leaking at the seam? A video wouldn't hurt.

To answer your original question, I have seen Marine Tex work (not jb weld) and can be fairly easily removed. You won't fill the gap, you will "Bridge" across the gap ~1/8"thick. Removing the paint, adding tooth, and squeaky clean(acetone multiple times) is a must.

 

[Johnson209]

Re: 1975 15 hp johnson leaking gas on its side

Have you tried tightening the bolt? Tearing that motor down isn't remotely cost effective and if pulling the flywheel seems like a headache, you won't like the process and expense.

Are you sure it's leaking at the seam? A video wouldn't hurt.

To answer your original question, I have seen Marine Tex work (not jb weld) and can be fairly easily removed. You won't fill the gap, you will "Bridge" across the gap ~1/8"thick. Removing the paint, adding tooth, and squeaky clean(acetone multiple times) is a must.

As I was prepping to take off my fly wheel I saw yr post. I think I'm going to try yrs first. If all else's fails I think then I will take the head off. I just don't like to get my hands dirty only if I have too I did tried to tighten the bolt that didnt work. I'll see if I can post a video of the leak.

 

[boobie]

Re: 1975 15 hp johnson leaking gas on its side

I've used Marine Tex for years and it really works good if you prep the surface properly. If you do try it, get the gray.

 

[Johnson209]

Re: 1975 15 hp johnson leaking gas on its side

I've used Marine Tex for years and it really works good if you prep the surface properly. If you do try it, get the gray.

Going to order me a bottle since none the stores here carries any. Grey it is.
Thks

 

[dazk14]

Re: 1975 15 hp johnson leaking gas on its side

FWI - You do NOT want the rapid set that comes in tubes. The good old fashion product that comes in a box - with glass jars of unequal sizes. 2oz. About $13 retail.
Good call by boobie on the color, I forgot they even sell the white. For an important repair, I suggest mixing the entire contents, so the ratio is perfect. It takes a while to cure - LET IT.

I would still post a vid.

 

[Johnson209]

Re: 1975 15 hp johnson leaking gas on its side

before going futher, heres a quick video i post up on youtube. Some how i cant post it on here.
My Movie - YouTube
Please let me know what you guys think. The weather is getting hot in california and I want to get this baby in the water =)

 

[RogersJetboat454]

Re: 1975 15 hp johnson leaking gas on its side

before going futher, heres a quick video i post up on youtube. Some how i cant post it on here.
My Movie - YouTube
Please let me know what you guys think. The weather is getting hot in california and I want to get this baby in the water =)

Looks like she's blowing out that seam pretty good...

 

[Chinewalker]

Re: 1975 15 hp johnson leaking gas on its side

Fix it right! If it's blowing fuel out, it's running lean on that cylinder, which can cause piston scuffing and eventually a blown motor. Won't take you but a day or a few evenings to get it apart and seal it up. Then you won't have to worry about it...