1976 70 HP Johnson - Running "Rich"

[capnstabbin]

I got a 1976 70 HP Johnson that I have been told is running "rich"...

They said that my carbs may need to be adjusted

This came about because I saw leaking from the exhaust cover a burnt oily gas mixture that drips after every ride.

I leave my boat in a slip all season in an already polluted river, I dont want to make it any worse.

Now, last season I took the carbs apart and re-did them and I even replaced some warn parts ( i.e. floats, pins, and gaskets)

What should I do to tackle this problem?

These forums are great but sometimes with not enough information the replies are useless. For example here is my last post about this same problem,

http://forums.iboats.com/showthread.php?t=431385


Let me know if I need to provide more info.........

 

[mrcj001]

Re: 1976 70 HP Johnson - Running "Rich"

These forums are great but sometimes with not enough information the replies are useless.

It seems like other members have come up with a conclusion with the problem you have.

If you tackle the job yourself, you will need a service manual for your engine.

If not, pay a marine service center to do it for you.

You can get a manual for your engine here:
http://www.outboardbooks.com/

 

[capnstabbin]

Re: 1976 70 HP Johnson - Running "Rich"

I have a manual, I think on the last thread the problem is I mention the gas was burnt, actually its not....

 

[Chinewalker]

Re: 1976 70 HP Johnson - Running "Rich"

How do your spark plug tips look? If you're running rich they will be very dark in color. What plugs are you running? You should be running Champion L77JC4s.

 

[Haffiman]

Re: 1976 70 HP Johnson - Running "Rich"

To be honest, you are in for a big project that might turn tricky.
A 35 year old engine and never been apart?
Load up with propane as a lot of screws will be corroded and will need heat to come loose.
Do some training in drilling out broken bolts as quite some will 'loose their heads' as you try to get them off.
Then you need a proper stand for the engine to work on and some sort of lift to get the powerhead off and back on.
If you are still willing to proceed, I'm sure someone will be around assisting with solving problems that might occur, but remember we are not able to do the actual job and need correct info in order to be able to assist.
You even have the cost aspect to consider:
1 gasket kit complete
3 set of std piston rings
1 impeller and thermostat (most likely)
1 Gearcase sealing kit (put in calculation)
min 250 in 'un-expeted'.
Still willing to proceed?
Go through your manual, hopefully an OEM!!!
Start preparing for removing the powerhead.
If frozen to the drive-shaft, come back and we will help you!
Good luck.

 

[capnstabbin]

Re: 1976 70 HP Johnson - Running "Rich"

What is it? Why do I have to take the power head off, from what I have been reading, the carbs just need to be adjusted.... am I wrong? Why again am I taking the power head off and changing the rings>?

 

[capnstabbin]

Re: 1976 70 HP Johnson - Running "Rich"

And yes I'm willing to proceed..........send all the help you can.

The manual I have is original OEM and I even picked up parts catalog from 1976 as well all OEM, it has plenty of exploded views of the powerhead.

If I go through with it, which it looks like I'm gonna, I post as many pics of everything and anything regarding this engine.

Are there any photos you would like to see that may get you thinking more about what my problem is?

My big worry is that yes this engine is 35 years old, yes it is running now, but what if I put it all back together and it doesn't work. Just for a dripping oil problem.

 

[Haffiman]

Re: 1976 70 HP Johnson - Running "Rich"

I took your time to read your first post and look at the pics.
Here is a 'copy and paste' from one of your posts:
'I wanted to do the piston rings anyway at the end of the season... I mean if I am keeping this engine... and dont plan on buying something else... is it worth doing all this work? is the engine worth it... I was thinking of getting something that didnt dump so much gas and oil into the bay.....going green I guess'.

It is not possible to change the rings without lifting the powerhead!

The oil-leak, if un-burnt, is most likely from either carbs or intake, but impossible to know without starting to tear down.
It may even be as simple as from the air-box in front of the carb.
But as I said, we are not there, you are.
How deep you want to dig into the engine is your decision.
I just wanted to point out that there will be costs, there will be problems.
I do not want to 'trick' anyone into starting a job they do not finish.
I have seen too many 'experienced' mechs fail in an operation like this, but if determined it is not impossible even for an un-experienced with some guidance from those who are experienced.

 

[Haffiman]

Re: 1976 70 HP Johnson - Running "Rich"

Check out hose #49 and I believe you find your 'leak'.

 

[capnstabbin]

Re: 1976 70 HP Johnson - Running "Rich"

OH OK. and let me thank you now for the info you have provided me with so far. Yeah Im sorry I have been all over the road with this.... but the main point here is that I find the leak, and engine runs another season.
This boat, unlike many others, owes me absolutely nothing. I have enjoyed every minute using it and fixing it. ( Maybe not the minutes waiting for a tow or driving through a "White Squall" with this finicky motor)

OK, so, this HOSE #49 attaches to #29 on the air silencer right. I think I need to take a picture of that area and attach it to this post. Lets start there since it seams to be the source and the easiest fix I would assume.

If I take that silencer off and remove the hose, what direction does the oily gas mixture supposed to travel to and from?

Does it flow or drain from front of carb to back of carb or the other way?

Not sure what that hose does

 

[Haffiman]

Re: 1976 70 HP Johnson - Running "Rich"

It is supposed to suck the 'spit-back' ,from the carburetors that gets collected at the bottom of the air box , through the hose and into a suction nipple at the bottom of the intake manifold #36.

 

[capnstabbin]

Re: 1976 70 HP Johnson - Running "Rich"

OK Here are some photos, I could not get a good photo of tube going to the #36 but I did check it, its attached.

What if I'm getting alot of spitback what would that be from?, Wouldn't the spitback look clearer, not burnt like whats on my finger, where does it go once its sucked into the manifold?

 

[Haffiman]

Re: 1976 70 HP Johnson - Running "Rich"

Taste it!(Or smell it)
Taste carbon - it is burned and comes most likely from exhaust system.
If not burned, from engine front.
Pics tells a lot, but has no smell or taste.
If 'burned', the most likely source of 'leak' is the gasket between powerhead and exhaust collector (leg).
Given the age of the engine, quite normal it is burned through.

 

[capnstabbin]

Re: 1976 70 HP Johnson - Running "Rich"

is that gasket a pain to fix.... what numbers are we talking about on exploded view above?

 

[capnstabbin]

Re: 1976 70 HP Johnson - Running "Rich"

And what would you compare the taste of carbon to?.... I might go out there and taste it.... no really I think I can smell it burnt like carbon I am assuming.

 

[Haffiman]

Re: 1976 70 HP Johnson - Running "Rich"

Gasket is not on that pic.
Powerhead must be lifted off.

 

[Fed]

Re: 1976 70 HP Johnson - Running "Rich"

I'd give it a good degrease and then see exactly where the oil was coming from.

 

[mrcj001]

Re: 1976 70 HP Johnson - Running "Rich"

Looks to me like the fuel coming from the carbs. If you are putting the engine in trailering tilt, it will do that.

If not, the floats are sticking sometimes and flooding.

 

[capnstabbin]

Re: 1976 70 HP Johnson - Running "Rich"

OK the boats been out of the water for a few days now, and the motor has been all the way down, no trailer tilt, as if I was running.

Normally when its in the slip for the season, after every ride we pull the motor up out of the water to keep the out drive out of the water...less barnacle build up.

When its tilted up, for sure the carbs leak a little spit back... its done that ever since I have owner her.

But recently... the drip has started out of the exhaust housing when I put the motor in a tilt position ....shown in the first picture. This drip is burnt and oily

Since its been out of the water sitting in the driveway, with the motor in the down position, the drip seems to travel all the way out , down to the prop, shown in the second picture. It drips down the skeg, but pic shows motor in up position. This drip is also burnt and oily.

?????I would assume also that the oily burnt discharge is sent out the exhaust normally when running in the water or where is it supposed to go opposed to leaking like it is?????

This must be the gasket you speak of under the power head? I am actually not sure which gasket you mean. and is that it.

 

[capnstabbin]

Re: 1976 70 HP Johnson - Running "Rich"

Oh boy is this it? #50.... looks like a lot of work for a 4 dollar gasket, no?
See attached photo