1966 Johnson 80hp outboard

[Newbie-boater]

Just purchased a 1966 aluminum hull boat with a 1966 Johnson 80hp outboard motor. As I run the engine there is a very distinct miss every 5 - 7 seconds. I changed the spark plugs, cleaned the distributer cap/rotor. The engine is still missing. Can anyone help?

 

[racerone]

Open the low speed mixture needles.

 

[boobie]

Do a cylinder drop test on it when it's acting up.

 

[Newbie-boater]

Racerone I did that and the engine stalled. Could it be the points on the top part of the distributor cap?

 

[boobie]

Could also be a bad coil.

 

[jimmbo]

Your engine can be either a Battery Ignition(electric shift model) or a Magneto Ignition(mechanical shift model). Both systems use a single coil. Bad wires, one set of points-condensers could be bad. Loose or intermittent shorts to any wire in the ignition system.
It died when only one of the plug wire was pulled? May be more than one issue here, or it is only running on 1 1/2 cylinders.
Well you are going to need to check if you have spark to all cylinders, a good spark should be able to jump about 1/4" gap.
A gummed up/dirty/misadjusted carb side can wipe out 2 cylinders

 

[Newbie-boater]

I don't have tool or lots of knowledge, frankly I don't have money to bring the engine in to be fixed. What are sme simple things a newbie can check? Should I be running premium gas or is regular ok?

thanks for the help.

 

[jimmbo]

Regular is fine, just use a good TC-W3 oil at 50:1.
Check for a good spark at all the cylinders
Make sure the carbs are clean and the mixture screws are properly adjusted.
On an old engine, it is wise to do a compression test to see if it even worth spending any time. let alone money, to try get it to run properly

 

[F_R]

Just when is this miss happening? Idle? Wide open throttle? In between? If at high speed, you wouldn't be the first one to mistake a jumping clutch dog for a miss. A clutch dog issue gives a very distinct thud, usually described as feeling like you ran over a submerged object (or a gator here in the south).

 

[Newbie-boater]

F_R that is exactly the problem. How can I fix a "clutch dog" problem?

 

[racerone]

Model # is ??-----Or does it have electric shift , yes or no ?

 

[F_R]

If it is a clutch dog, it is manual shift. There is no clutch dog in electric shifts. But that doesn't mean an electric shift can't jump and slip too.

If it is a clutch dog jumping, the lower unit gearcase has to come apart to replace it. And most usually the forward gear also. The longer you wait, the worse it will get, and may damage other parts also. Every time it jumps, it is like a little guy in there beating on it with a big hammer.

 

[Newbie-boater]

I was afraid it was something in the lower unit. Thanks for your help.

 

[racerone]

Testing / inspection needs to be done.