Johnson 115 Flatback

[turfman]

Hi everyone.

I'm new here and have a question.

I just recently purchased a 18ft CC with an 84, 115 Johnson flatback; I was told.

Model #J115TLCRD

I've never heard of a flatback before. Did I make a mistake in buying this engine. Runs good ;but I like to stock up on spares and this motor seems to be an oddball.

thanks
Mark

 

[Chinewalker]

Re: Johnson 115 Flatback

Hi Mark,
Nothing at all wrong with that design. It's a 1984 model year (the CR suffix near the end gives the year where C=8 and R=4 out of the OMC code word INTRODUCES).
The "flatback" term merely refers to the type of cover between the cylinder banks. The 85 to 115 hp model up to 1984 had a flat cover, while the 135 and 140 models had a "bubble back" which incorporated an additional expansion chamber to help with exhaust tuning to help get the extra horsepower. I have a 1984 Johnson 90 on my boat and it is a solid performer. Your 115 is 96% the same motor as mine, with the differences being in porting, cylinder heads and carburetion changes.

LOTS of similar motors out there should you need parts for it. Many different years on either side of yours will interchange in part or whole...

- Scott

 

[turfman]

Re: Johnson 115 Flatback

Thanks Scott.

I was just hoping it wasn't a special run or something rare.

thanks again
Mark

 

[F_R]

Re: Johnson 115 Flatback

Actually, the "flatback" was the original design starting with the infamous fat-fifty of 1958. Many thousands of them were made. That's not to say there weren't a ton of changes through the years. The bubbleback didn't appear till 1973-ish.