1976 Johnson 15 HP

LastCastIPromise · Jan 21, 2018

Hello all!

I recently picked up a 16' jon boat that came with a 1976 15 HP Johnson. It started right up when I went to look at it and the guy I got it from told me that he had it on the water earlier that year. I would like to get this thing out in the spring, so I have a little bit of time to work on it.

My question is, are they are typical maintenances that should be done for peace of mind before getting it out on the water? I have read several posts talking about complete overhauls and water pump changes.

I would love to hear your thoughts!

Thanks!

Weldorthemagnificent · Jan 21, 2018

Impeller in the water pump is a peace of mind. Might be working fine but cost 30 bucks to replace and then you know how old it is. Other than that, if it runs fine I wouldn’t tear into it. Run premium non ethanol if you can and I swear by seafoam. I put a bit in every tank, keeps the carb spic and span. Visual inspection for possible problems; wires, hoses, recoil rope...
good luck with your new rig.

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timsmcm · Jan 21, 2018

Since it is a 76 model and the guy only told you that he had it on the water and that is all, the first thing I would do is change out the water tube gromets, complete oem water pump kit, dump the lower unit oil to see if any water, fresh plugs. Look under the hood for any dry, crumbly wires. And do a seafoam carbon clear. That should get you started.

LastCastIPromise · Jan 21, 2018

timsmcm said:
Since it is a 76 model and the guy only told you that he had it on the water and that is all, the first thing I would do is change out the water tube gromets, complete oem water pump kit, dump the lower unit oil to see if any water, fresh plugs. Look under the hood for any dry, crumbly wires. And do a seafoam carbon clear. That should get you started.

Would Sierra kits be ok, or would you shy away from those?

LastCastIPromise · Jan 21, 2018

Here are a few pics under the hood. Should be able to zoom in on them.

Pappy · Jan 22, 2018

LastCastIPromise said:
timsmcm said:

Since it is a 76 model and the guy only told you that he had it on the water and that is all, the first thing I would do is change out the water tube gromets, complete oem water pump kit, dump the lower unit oil to see if any water, fresh plugs. Look under the hood for any dry, crumbly wires. And do a seafoam carbon clear. That should get you started.

Click to expand...

Would Sierra kits be ok, or would you shy away from those?[/quote

Buy OEM parts! Buy OEM parts! Buy OEM parts!
Sierra parts are notorious for not being quite right in fit. Points are terrible, impellers have a history of all kinds of fit issues as well. Get a complete WP kit and by all means check the water tube grommets as has been mentioned. Not an easy task but you can do other services while in there. Other checks have been mentioned.

Crazyboat · Jan 22, 2018

I had a 74 of the same engine, was a work horse and was built proof. Change what was mentioned above and run her hard, put her away wet, she don't mind, just lube her up before storage and your set IMO.

timsmcm · Jan 22, 2018

One more thing, change all of that old rubber gas line. And pull the cover off the fuel pump and check the screen.

LastCastIPromise · Jan 22, 2018

Crazyboat said:
I had a 74 of the same engine, was a work horse and was built proof. Change what was mentioned above and run her hard, put her away wet, she don't mind, just lube her up before storage and your set IMO.

Can't wait to give her a try!

LastCastIPromise · Jan 22, 2018

Gents I really appreciate the feedback! I have the OEM WP kit ready to order along with other items for the install.

I could go down the rabbit hole with this I think... watched a video on changing lower unit seals and I don't have half the special tools required for that job..

LDUBS · Jan 22, 2018

LastCastIPromise said:
Gents I really appreciate the feedback! I have the OEM WP kit ready to order along with other items for the install.

I could go down the rabbit hole with this I think... watched a video on changing lower unit seals and I don't have half the special tools required for that job..

Is changing the lower unit seals a preventative need or is there some indicator that they need to be changed? I don't know the answer, but wonder if everything looks OK (gear lube?) then do they need to be changed. I'll admit I'm on thin ice here.

Pappy · Jan 22, 2018

If there is no water in the gear oil then there is no need to change any seals.
I would change the fill and drain screw washers just as a peace of mind issue.

ProduceMan · Jan 23, 2018

Pappy are those washers single use only?

LastCastIPromise · Jan 23, 2018

Lastest pics

Fuel screen looks pretty clean, but the plugs not so much. I will be replacing the plugs toward the end after the carbon clean. Also noticed that the rubber fuel hose was held on by zip ties. That can't be normal right?

Stumpalump · Jan 24, 2018

I've got a 1976 15 HP Evinrude (same motor) and just sold another just like it. One weakness is the knob on the side for idle adjustment that breaks. Easy to replace with a 90 degree snap ring plyer. The coils go bad. It may start and run and then loose power or sound like its knocking. I had one that sounded like a cracked piston but it was a coil. If your going to keep it for a long time then it's not a waste to shot gun it. Put in a fresh water and fuel pump, replace all fuel hoses (zip ties are common), keep both ignition coils in mind and don't hesitate to replace if you see any small cracks in them and it runs weird. Cracks are caused by corrosion inside or overheating. The coils biodegrade in 42 years anyway. A carb cleaning and carb kit install was not suggested. They are a little tricky to get off but if your real good with your hands and have an ignition wrench set then the carb is not impossible. It's probably due. Put a rag down the shift shaft hole because that's exactly where the carb nuts wind up. You will drop them. Run NGK B7HS plugs gapped to 30 thousandth. If you know how to ball park plug indexing then point the open end toward the carb. They don't idle as well as the 9.9 is why so don't think it's messed up if it won't idle real slow. If you pull the flywheel to check points then don't beat very hard on the flywheel nut. If it does not pop off with a very light plastic hammer then use a puller. The points don't work that hard and stay nice. Clean and check them. Condensers can fail like the coils and I had that problem. Reread all of Pappys post and follow to the letter then go to a site called "Leroy's ramblings" that will explain everthing in detail. You can buy starter rope by the foot at marine stores. If yours is original then it's time. Leroys site will explain it but look real carful under the starter for a tab that fits into a hole in the block. That tab must be in that hole and the starter need to be square before you start the starter bolt. You don't want to mess up those aluminum threads in the block. Clean the threads with a tap while the starter is off because at some point some monkey probably already had the starter off. Good luck! Very nice motor and why it still runs today.

Pappy · Jan 24, 2018

ProduceMan said:
Pappy are those washers single use only?

No, but after over 40 years they have to be ready to be changed and are dirt cheap.

LastCastIPromise · Jan 24, 2018

Stumpalump said:
I've got a 1976 15 HP Evinrude (same motor) and just sold another just like it. One weakness is the knob on the side for idle adjustment that breaks. Easy to replace with a 90 degree snap ring plyer. The coils go bad. It may start and run and then loose power or sound like its knocking. I had one that sounded like a cracked piston but it was a coil. If your going to keep it for a long time then it's not a waste to shot gun it. Put in a fresh water and fuel pump, replace all fuel hoses (zip ties are common), keep both ignition coils in mind and don't hesitate to replace if you see any small cracks in them and it runs weird. Cracks are caused by corrosion inside or overheating. The coils biodegrade in 42 years anyway. A carb cleaning and carb kit install was not suggested. They are a little tricky to get off but if your real good with your hands and have an ignition wrench set then the carb is not impossible. It's probably due. Put a rag down the shift shaft hole because that's exactly where the carb nuts wind up. You will drop them. Run NGK B7HS plugs gapped to 30 thousandth. If you know how to ball park plug indexing then point the open end toward the carb. They don't idle as well as the 9.9 is why so don't think it's messed up if it won't idle real slow. If you pull the flywheel to check points then don't beat very hard on the flywheel nut. If it does not pop off with a very light plastic hammer then use a puller. The points don't work that hard and stay nice. Clean and check them. Condensers can fail like the coils and I had that problem. Reread all of Pappys post and follow to the letter then go to a site called "Leroy's ramblings" that will explain everthing in detail. You can buy starter rope by the foot at marine stores. If yours is original then it's time. Leroys site will explain it but look real carful under the starter for a tab that fits into a hole in the block. That tab must be in that hole and the starter need to be square before you start the starter bolt. You don't want to mess up those aluminum threads in the block. Clean the threads with a tap while the starter is off because at some point some monkey probably already had the starter off. Good luck! Very nice motor and why it still runs today.

All I can say is wow! This information is fantastic! Thank you so much! I have been on the Leeroys Ramblings website and read a bunch of those articles, if not all of them. The side idle adjustment knob on this motor was broken when I got it.. I just removed the broken parts and have set them aside for now. I don't know if you noticed the coils in one of my pics above, but they coil itself looks relatively good.. it's the mounting surfaces that are very rusty. I don't know if that affects the coil internals or not.

I have worked on other motors before - tractors, vehicles, mowers etc. but this is the first outboard for me. As soon as my parts arrive i'll try and get more pics of the work and put them up on here.. Not sure if anyone else will find the information useful, but why not!

Once again, thanks to all for the information!

LastCastIPromise · Jan 27, 2018

I removed both spark plugs and did a compression test this evening.. got a reading of 110# on one cylinder and 111-112# on the second. While those numbers look good to me, I am not sure if it is common for the cylinders to read that close together, or if that may indicate an issue.

Any thoughts?

Thanks!

Weldorthemagnificent · Jan 27, 2018

The closer the better. If one is 125 and the other 95, that indicates a problem. Your numbers are good.

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LastCastIPromise · Jan 27, 2018

Drained the lower unit oil.. it came out kind of an olive color? No water leaked out of the drain plug when I opened it. It doesn't appear to be cloudy white.. hoping this is just old oil. I will be replacing the plug washers and refilling.

1976 Johnson 15 HP

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