115TL79R / 140TL79R engine cases

[rdenis]

Anyone know the case spec differences on the 1979 Johnson/Evinrudes 115 and 140. Are the cases physically bigger on the 140?

I have the shop manual on order but if anyone has the infor would be appreciated.

 

[ezeke]

Re: 115TL79R / 140TL79R engine cases

The crankcase sizes are standardized for the V4 engines in 1979. There is variation in porting for some horsepower ranges.

 

[rdenis]

Re: 115TL79R / 140TL79R engine cases

Interesting... which begs the next question whether upsizing from the 115 to 140 would make a good winter project - seems like 25HP more without adding prohibitive weight elements would be a good thing to try. I presume the heads on the 140 are high compression?

It'd be nice to find some engineered machine specs.

 

[Dhadley]

Re: 115TL79R / 140TL79R engine cases

On an Invader you might see some performance increases but probably not what you expect. The 79 140 porting and "tuned" exhaust may be a slight advantage. Just not a lot of torque differences.

However, hows the performance now? If the 115 isn't set up right and all you do is install a 140 powerhead the performance still won't be right.

 

[rdenis]

Re: 115TL79R / 140TL79R engine cases

I'm more interested in doing this from a technical/engineering side. I like challenging projects. The Invader itself is only rated for 115 HP so I wouldn't want to push it way past its limits. With the family on board she tops out at 37 MPH at 5500 RPM with a 17" pitch aluminum prop. With a 21" prop she turns 4600 RPM at 37 MPH so with a little more grunt maybe I could pickup some RPMS with the larger prop I have a 19" prop but have not run it). To be honest I'd be happy breaking 40 but the boat isn't built for speed.

Not sure how many more RPMS she'd turn with almost 22% more rated HP but I'm sure its not linear. But if I could get my 19" prop to turn 5500 at WOT, that would put me over the 40 mark for sure.

The other reason I would like a little extra grunt is yanking my wife out of the water on a slalom ski - she grew up with the boat but she struggles to get out of the water on one ski some 25 years after all those fun loving teen years!

 

[emdsapmgr]

Re: 115TL79R / 140TL79R engine cases

The 115 and 140 both used the rubber intake filler blocks that year. The 140 did use high compression heads. The carbs were different. You might want to consider converting to composite reeds. They idle nicely and have a nice mid-range response-which may help in pulling skiers.

 

[rdenis]

Re: 115TL79R / 140TL79R engine cases

Are you talking about a reed change just on the 115 or as part of upping to the 140?

 

[emdsapmgr]

Re: 115TL79R / 140TL79R engine cases

Both of those engines came from the factory with the same steel reeds. Conversion to composite reeds will make the engine more responsive through the rpm range. Further, installing them is easy if you have the engine apart for other performance changes. Since your engine already has the intake filler blocks, you may not have a reason to pull the intake manifold to install them... You may see a little rpm increase on top end with composites. They will make either engine run/perform better-in my opinion.

 

[rdenis]

Re: 115TL79R / 140TL79R engine cases

Great info - thanks - I'm going to rebuild her this winter so definitely making some notes. Any other suggestions for performance improvements - anything to be had on timing?

Also curious about splitting the cases on these beasts - any tricks there?