1992 Johnson 115hp bad cyl

[dreadinger]

I have a 1992 TJ115TLEND that has a bad bottom starboard cylinder. I am in the process of removing the power head but it appears that a ring broke and is wedged in one of the portsand there is only some slight scoring in the cylinder. The other cylinders look perfect. I just got this boat and motor knowing the motor was bad so I don't know what the old owner did. If all checks out to my advantage I plan on honing, a new piston and new rings all the way around. My question is with the "good" condition of the other cylinders what might have caused this failure?

 

[iwombat]

Re: 1992 Johnson 115hp bad cyl

Either carbon (coking) causing the rings to stick, or a clogged carb causing a lean condition.

In order to hone and re-ring you'll need to take everything out of the crankcase anyway. Since you're already committed to a new piston, why not go the next size over on that hole? You're looking at $50 or thereabouts for machining.

 

[Dhadley]

Re: 1992 Johnson 115hp bad cyl

Bingo! If the ring broke on the starboard side I'd bet it's due to coking from being lugged. Pretty sure you'll find the cylinders that look good are actually out of round. Lugging creates a lot of extra heat.

 

[dreadinger]

Re: 1992 Johnson 115hp bad cyl

just got off the phone with the old owner. He said the ear muffs fell off during flushing and it over heated but he shut it down before it seized up. I do not see any signs of heat any where on the powerhead. I have the lower end unbolted as well as the powerhead but can't pull it apart, the power will rock back and forth but will not lift off. I ordered a OEM manual that will be here in a couple of days. I traded a 14' jon boat setup worth 1200.00 for this boat. It is a 1992 Tracker Magna 19cCC that is in excellent condition so I have some room to play with.

 

[HybridMX6]

Re: 1992 Johnson 115hp bad cyl

Have you disconnected the shift linkage? If no, it's under the carbs, and that's possibly why you can't remove the powerhead. There is a weird little clip under the carbs, with a bolt that holds the shift rod. You won't be able to drop the lower unit either until you disconnect the shift linkage.

 

[dreadinger]

Re: 1992 Johnson 115hp bad cyl

No I didn't disconnect but I see what you are saying. That is crazy if I was just servicing the water pump, it looks like the carbs have to be removed to get to it. The Bible (manual) will tell me everything!

 

[Dhadley]

Re: 1992 Johnson 115hp bad cyl

The carbs don't have to be removed to disconnect the shift but since they have to come off anyway, they can if that's easier for you at this point. There's a clip on the starboard side. Pull the clip, push the rod and watch your toes.

 

[HybridMX6]

Re: 1992 Johnson 115hp bad cyl

The carbs don't have to be removed to disconnect the shift but since they have to come off anyway, they can if that's easier for you at this point. There's a clip on the starboard side. Pull the clip, push the rod and watch your toes.

LoL, you aint kiddin! Although for mine, it was pull the clip, unbolt the LU, then sit there and pry the LU off the midsection for 15 mins. I pulled about 5lbs of sand out of my midsection (bought a used motor with a dead cylinder, so I didn't care). I definately could see how that could go very, very bad though.
As Dhadley said, you don't have to pull them off, but since it's being removed anyways, and the carbs are as well, you may as well make your life a tad easier and do it now. That's how I got mine apart.

 

[dreadinger]

Re: 1992 Johnson 115hp bad cyl

Ok, I have decided to rebuild, I will be oversizing the cylinders. I just got my OMC manual to help me but would like any helpful tips I can get. After reading the manual I am wondering about special tools. I will be doing the work at my brothers aircraft maintenance shop so I will have most tools available to me. Can I improvise on the special tools?