1981 johnson 115 - skipping?

[matthewp]

I recently came into an old johnson - my dad had one 'laying around'. He did a few things before he gave it to me - new water pump impeller, thermostats, carb rebuild, and fuel pump. It starts and runs pretty well - idle is rough, though. I changed the lower unit oil last night - no signs of water contamination.

Anyhow, when underway, the motor will occasionally produce a single, pretty significant, skip (or catch, or whatever word). When it happens, it's as though the motor stopped running for a millisecond and caught again. It produces a big thud that can be felt throughout the boat. When it first happened, I thought I'd hit something. It only seems to happen after the boat has been running for about an hour.

ideas?

 

[tashasdaddy]

Re: 1981 johnson 115 - skipping?

does it keep repeating, over and over, or only is it just once occasionally?

 

[matthewp]

Re: 1981 johnson 115 - skipping?

Just once occasionally - usually after it's been running for over an hour. Two nights ago, it probably happened four times in the last half hour of my 2 hour outing. Last night, it only happened once over the course of two hours.

 

[tashasdaddy]

Re: 1981 johnson 115 - skipping?

check and make sure all your grounds are clean and tight.

 

[matthewp]

Re: 1981 johnson 115 - skipping?

Will do. Now that you mention it, the ground ring terminal coming from the motor is rusty. Thanks for the suggestion!

 

[wilde1j]

Re: 1981 johnson 115 - skipping?

If it continues and becomes more frequent, you're in for a new clutch dog and fwd gear. Caused by by slow, gentle shifting. Shifts should be quick and deliberate.

 

[matthewp]

Re: 1981 johnson 115 - skipping?

Unfortunately, little is known about the history of the motor - it actually came from your neck of the woods, wilde1j. My dad lives on the eastern shore of the chesapeak. He hasn't run it - it came on another hull he used for something else. I don't know anything about how the previous owner(s) shifted into gear. As for me, I belong to the deliberate shifters club. there was no debris in the lower unit oil when I changed it, though I know that might not mean anything.

 

[tashasdaddy]

Re: 1981 johnson 115 - skipping?

let's hope it is not the clutch dog, that was my first impression, but it is not really frequent enough.

 

[matthewp]

Re: 1981 johnson 115 - skipping?

well......
I cleaned up my contacts... no improvement. In fact, it IS getting worse. It happens more frequently at lower rpms, but it will still happen when on plane, just less. putting through the no wake zone tonight, it was clear that something was coming disengaged with the drive train. My thought was that perhaps I didn't adjust the shift cable properly, but it doesn't make that grinding sound you get when shifting slowly. Thanks for the input. What all is involved with clutch/forward gear replacement. I'm pretty handy. I haven't checked to see if it happens in reverse. It definitely does not happen when out of gear.....

bracing for the worst,
Matthewp

 

[wilde1j]

Re: 1981 johnson 115 - skipping?

Matthew, get or look at an OEM shop manual to see if you want to mess with it or not. If the motor's seen salt, it may be a bugger to get the bearing carrier out, which is needed as an early step in the disassembly process. It not real hard, but can be a challenge if you've never done it before.

 

[matthewp]

Re: 1981 johnson 115 - skipping?

Is there anything else I can do for a positive diagnosis before I start pulling things apart? Thanks for your input, guys.

 

[matthewp]

Re: 1981 johnson 115 - skipping?

It's the clutch dog. After reading some posts about similar symptoms, it seemed like a clear case. I went home last night and engaged the forward gear (motor not running, mind you) and spun the prop. I could turn it - it was catching/not catching on the dog. I adjusted the shift cable to move the shifter farther when engaging the forward gear. I took the boat out for a half hour - no clunk at any rpm. Time will tell.

I know I'm not out of the woods. I think it was Tashasdaddy who offered advice on this same scenario - probably delaying a rebuild for a little while. I know I've done the lower unit no favors. To others within ear shot - (particularly newbies like me) - be sure your shift linkage is spot on when swapping motors or monkeying with it for any other reason.

Thanks for the ongoing help and information. Iboats is a great site!

 

[ezeke]

Re: 1981 johnson 115 - skipping?

You may have a spun prop. Have you checked that?
Check by scribing a line as shown below, using the cotter pin as a pointer. If the alignment moves, fix the prop.

 

[matthewp]

Re: 1981 johnson 115 - skipping?

I did consider that, ezeke. I mostly ruled out the spun prop because it wasn't acting like one (over-reving engine, no speed - more frequent at higher rpms). I've never experienced a spun prop, but from what I can tell, it's not unlike a slipping clutch on a car. My noise was more frequent at lower rpms. I will mark the prop, though. Can't hurt to know either way.

 

[ezeke]

Re: 1981 johnson 115 - skipping?

Probably not, but worth checking before going in, just like being sure that the shift rod is set exactly right.

 

[joho5]

Re: 1981 johnson 115 - skipping?

sometimes if the carb is closed up too much, it can cause a "miss" or skip. I have a little chrysler that was doing the sam exact thing and I opened it up a bit (of couse mine only has a low speed setting) and it quit.

 

[wilde1j]

Re: 1981 johnson 115 - skipping?

What Matthew described is not an engine miss, it is the typical symptom of popping in and out of gear, which produces a violent lurch and is very different than an ignition or fuel related miss.