60 hp Johnson - choke makes it run better?

The Grail

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May 1, 2007
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What a great site! I'm new to boating and have learned a lot from this forum in the last few weeks trying to fix the ailing Johnson I bought with a 1962 MFG 15 footer. I've searched many postings and still have some unresolved problems. I'll try to be brief while listing the things I need help with.

1. What year and model is it? It's a 60 hp Johnson three cylinder with Hydro Electric shift. The plate on the transom bracket is missing (I can see where it used to be) and the welch plug on top of the motor only lists a serial #: J3489149. I haven't been able to find a model # anywhere. I've narrowed it down to either a 1970 or 1971. The local Johnson dealer ran the serial number with BRP and said they couldn't find it. I've checked the BRP diagrams, and could not see differences in the two model years. Can anyone point me in another direction? Does anyone know if the 1970 and 1971 models were so identical that specs and parts were the same for all eight 60 hp models listed?

2. What's wrong with it? The motor stopped abrubtly at full throttle on my second time out, though it wasn't running great before then. I found that it was getting gas, but not spark. I replaced the surface gap plugs with Champion QL77JC4 plugs, gapped at .030. I checked the points and they're gapped at .010. I cleaned all contacts on the rotor, checked wires and connections. It started and ran better than before (on the hose), so I put her in the water. Idled fine, but when I increased the throttle, it didn't increase rpm. (The linkage is working) It sounded like it was about to bog out, and sometimes it did. However, with the throttle increased and bogging, when I activated the electric choke with the toggle switch by the key, she revved up. It then ran well (as well as it ever had for me) as long as I left the throttle up, but if I let it idle, I had to choke it momentarily to get it going well again at higher rpms. This happened repeatedly. Has this happened to any of you?

I have not done the seafoam treatment yet, and was trying to avoid rebuilding the carbs, especially without knowing the model number. I drained and cleaned the gas tank and used new gas before I started it the first time.

3. Gas and oil mix - Is it still 50:1, or does an older motor need more oil?

I appreciate any help any of you can give me. Thanks.
 

Curtisimo81

Cadet
Joined
Aug 12, 2006
Messages
14
Re: 60 hp Johnson - choke makes it run better?

don't know if this will help, but from reading on here i have read that some of the older motors take leaded gas. Not sure if that is the case with your motor, but would be something worth looking in too. Not sure if it would cause those problems but, i'm an auto technician, not a boat tech.
 

F_R

Supreme Mariner
Joined
Jul 7, 2006
Messages
28,219
Re: 60 hp Johnson - choke makes it run better?

The fact that you have to choke it indicates that the carbs are dirty, especially the high speed orfice jets in the very bottom of the carb bowls. Even a thin trace of gum or varnish in there will cause your problem.

What's worse is that it causes the motor to run lean (that's why it runs better if you richen it with the choke) Running lean will burn pistons and break rings due to pre-ignition. You gotta fix it and not keep running it that way.

Yes, the fuel mix is 50:1
 

The Grail

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Joined
May 1, 2007
Messages
23
Re: 60 hp Johnson - choke makes it run better?

My apologies for taking so long to respond. The day after I posted this, I came upon a good deal on a larger boat and motor and have been occupied with that until this week. (Stay tuned for questions on that one!) This week I have been focused on trying to get my Tahoe running, because now it has no spark. I've looked, but I haven't found an auto forum anywhere close to this forum in detail and responsiveness.

I'm still trying to figure out the year of the 60 HP Johnson, so I can get the correct manual and parts. Thanks to those that responded. Imported_F_R, it makes sense about the carbs being dirty. I'll let you know how it turns out after I rebuild them.
 

F_R

Supreme Mariner
Joined
Jul 7, 2006
Messages
28,219
Re: 60 hp Johnson - choke makes it run better?

Offhand, I can't think of any significant differences between 1970 and 1971. If it has the original paint and decals you can go to http://www.old-omc.de/ and compare with the original sales brochurs
 
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