merc 115 inline difference from 70' to 80's ?

[quebec#1]

Whats the difference from a 1978 merc inline 115 hp to a 1985 merc 115 hp inline 6cyl ?

 

[AMD Rules]

Re: merc 115 inline difference from 70' to 80's ?

Clams Canino has brief decription on his ebay page describing some of the most notable milestones of the 99ci inline six evolution as follows:

"In 1970 the new "direct charge" powerhead came out. The 1970,1971 Merc 1350 (135hp) as well as the 1970, 1971, and 1972 Merc 1150 (115hp) all used this new powerhead. Also I can convert those early 115's to 135's for a small additional fee. This cannot be done with the 1972 and up powerheads.

The 1972 1400 (140 hp) marks the beginning of the "new" exhaust ports and base gasket / bolt pattern. This pattern lasted to the end of the inline six. In 1973 the 115 also got the new bolt pattern. This means that (with the exception of the 1972 115 that interchanges with '70 and '71) all the distributor ignition inline six powerheads made from 1972 to late 1979 will bolt on interchange. Also, this means that you can bolt a 140 or 150 onto a 115 leg to upgrade your outboard - the only difference in the powerhead is the internal porting. You cannot convert these 115's to 140/150 hp version, the internal porting is radicly different. But you can bolt a 150/140 powerhead to the 115 leg with no problem at all, the lower units are all the same. Also the 1972 140 is a "true 140". But, the later 70's 140's are identical to the 150's. Once Mercury came out with the V-6 150 in the mid-70's, the marketing guys renamed the 1500 inline to a 1400 so as to not have two 150's competing against each other.

Lastly, In late 1979 mercury did away with the distributor ignition and went with the modern ADI ignition. In 1982 they re-rated the powerheads to "propshaft HP" as opposed to earlier "crankshaft HP". The old 115 was called a "90" and the 140 became the "115". All the ADI ignition powerheads will interchange."


- The 1978 Merc 115 is crankshaft rated, distributer ignition.
- The 1985 Merc 115 is prop rated, ADI ignition.
- Internally, the intake and exhaust porting will be considerably different between the two.
- Carb orifice/jetting will be different, the older motor having a conventional choke system, whereas the 1985 has an enrichment valve.


.

 

[bexi]

Re: merc 115 inline difference from 70' to 80's ?

so my 1977 model 115 that just blew up is really only 90hp prop but my new 1983 115 with adi ignition is 115hp prop?

so i'm going to have a whole lot more power????

 

[quebec#1]

Re: merc 115 inline difference from 70' to 80's ?

Thanks for the great info !You just answered my question (In 1982 they re-rated the powerheads to "propshaft HP" as opposed to earlier "crankshaft HP". The old 115 was called a "90" and the 140 became the "115)
I bought a cvx 16 with a 1985 merc 115 and a budy on the lake has an older one with a 78 or 79 merc 115 that he thinks will beat the crap out of me but i thought i had the advantage with the newer motor.

 

[quebec#1]

Re: merc 115 inline difference from 70' to 80's ?

Would the compression be higher or lower on the 1970's engines vs the 80's ?

 

[Lone Duck]

Re: merc 115 inline difference from 70' to 80's ?

Clams Canino has brief decription on his ebay page describing some of the most notable milestones of the 99ci inline six evolution as follows:

"In 1970 the new "direct charge" powerhead came out. The 1970,1971 Merc 1350 (135hp) as well as the 1970, 1971, and 1972 Merc 1150 (115hp) all used this new powerhead. Also I can convert those early 115's to 135's for a small additional fee. This cannot be done with the 1972 and up powerheads.

The 1972 1400 (140 hp) marks the beginning of the "new" exhaust ports and base gasket / bolt pattern. This pattern lasted to the end of the inline six. In 1973 the 115 also got the new bolt pattern. This means that (with the exception of the 1972 115 that interchanges with '70 and '71) all the distributor ignition inline six powerheads made from 1972 to late 1979 will bolt on interchange. Also, this means that you can bolt a 140 or 150 onto a 115 leg to upgrade your outboard - the only difference in the powerhead is the internal porting. You cannot convert these 115's to 140/150 hp version, the internal porting is radicly different. But you can bolt a 150/140 powerhead to the 115 leg with no problem at all, the lower units are all the same. Also the 1972 140 is a "true 140". But, the later 70's 140's are identical to the 150's. Once Mercury came out with the V-6 150 in the mid-70's, the marketing guys renamed the 1500 inline to a 1400 so as to not have two 150's competing against each other.

Lastly, In late 1979 mercury did away with the distributor ignition and went with the modern ADI ignition. In 1982 they re-rated the powerheads to "propshaft HP" as opposed to earlier "crankshaft HP". The old 115 was called a "90" and the 140 became the "115". All the ADI ignition powerheads will interchange."


- The 1978 Merc 115 is crankshaft rated, distributer ignition.
- The 1985 Merc 115 is prop rated, ADI ignition.
- Internally, the intake and exhaust porting will be considerably different between the two.
- Carb orifice/jetting will be different, the older motor having a conventional choke system, whereas the 1985 has an enrichment valve.


.

I have a 81 90hp can I change power head to a 82 hp 115 ? on the same leg?

 

[jimmbo]

Re: merc 115 inline difference from 70' to 80's ?

Would the compression be higher or lower on the 1970's engines vs the 80's ?

In 1984 Merc started using a new "low dome" piston. It did drop the mechanical compression a bit.

 

[jimmbo]

Re: merc 115 inline difference from 70' to 80's ?

I have a 81 90hp can I change power head to a 82 hp 115 ? on the same leg?

complete power head, carbs and linkage, and exhaust tuner/tube and you will the swap will be complete

 

[quebec#1]

Re: merc 115 inline difference from 70' to 80's ?

Would the 1985 merc 115 be comparable in hp vs a 1985 johnson 110 hp ?
Did johnson also go by "propshaft HP by the mid 80's ?

 

[Lone Duck]

Re: merc 115 inline difference from 70' to 80's ?

complete power head, carbs and linkage, and exhaust tuner/tube and you will the swap will be complete

Thanks! Think I'll look into that.

 

[jimmbo]

Re: merc 115 inline difference from 70' to 80's ?

Would the 1985 merc 115 be comparable in hp vs a 1985 johnson 110 hp ?
Did johnson also go by "propshaft HP by the mid 80's ?

If the 110 has the bubbleback exhaust cover then yes they would be comparible. BTW Bubbleback 110s and 115s are the same engine
OMC swithed to prop rating on the V blocks the year the V4 loopers were introduced. 1985, I believe

 

[quebec#1]

Re: merc 115 inline difference from 70' to 80's ?

Im just trying to compare with my gt 150 that i sold last spring and the current cvx 16 with the merc 115.
The merc was a bit louder than the 1986 johnson 110 but felt smoother.
As for power it was hard to tell, i only had two runs with the boat before i put her away for the winter.
Thanks for the great info !
My johnson looked like more of an engine but i guess wide vs skinny can be deceiving !

 

[quebec#1]

Re: merc 115 inline difference from 70' to 80's ?

Is this a bubble back ?

 

[jimmbo]

Re: merc 115 inline difference from 70' to 80's ?

I think so, but a picture of the engine with the cowl off will tell me so. As for the 'tower of power' vs. the 'fat four'? Both engines are just under 100 cubic inches, 99.6 for the V4 and 99.8 for the inline. The merc should be a wee bit smoother having an extra 2 cylinders.

 

[bexi]

Re: merc 115 inline difference from 70' to 80's ?

Can someone answer my question?:


so my 1977 model 115 that just blew up is really only 90hp prop but my new 1983 115 with adi ignition is 115hp prop?

so i'm going to have a whole lot more power????

 

[AMD Rules]

Re: merc 115 inline difference from 70' to 80's ?

Bexi,

That's correct. The 83 is prop rated.

I did the same conversion, from '72 115hp to '84 115hp and it is a noticeable increase in power.

 

[bluepartsman]

Re: merc 115 inline difference from 70' to 80's ?

I am currently switching from a 1978 inline 1150 to a 1977 inline 1500 on my baja 16'. Will I be noticing an increase in power and speed?

Also my friend has an early 80's (1982?) v-4 115 evinrude on a 15' glastron. Does anyone have expirence with what set up will be fastest if I use my merc 1500. I know there are a lot of other variables but what motor should out perform the other?

I didn't get a chance to get out on the water with him last year when I had my merc 1150 hooked up but form what is said above, if my 70's era 1150motor is really only 90hp prop rated to his 115hp prop rated evinrude he should be able to pull away. And if my 1500 is really about 115hp prop rated it should be close to his v-4 evinrude.

 

[Chris1956]

Re: merc 115 inline difference from 70' to 80's ?

Blue, The Merc 1500 has 35 HP more than the Merc 1150. Whether you can notice this depends on the prop and hull design. Some boats only go so fast no matter how much HP you hang on them.

BTW-you guys are getting a bit carried away and interpreting Clams description a bit too literaly. Do an analysis of the power loss caused by the gearcase, and you will know how much propshaft power a powerhead-rated motor has. You will find the difference is not 25HP, as is suggested by the 115HP becoming the 90HP.

 

[AMD Rules]

Re: merc 115 inline difference from 70' to 80's ?

Here's some additional discussion on this topic, and comparisons to published dyno values (in psi) between various motors:

TMD The Dyno Run

There is even a video of a sample dyno test:

TMD The Dyno Run - the video


.

 

[Droll]

Re: merc 115 inline difference from 70' to 80's ?

BTW-you guys are getting a bit carried away and i**as is suggested by the 115HP becoming the 90HP.

Clams Canino has brief decription.....

The 1400 became a 115, BUT not without some internal changes :

• Low dome pistons....don't know when, but some earlier 1500 also came with low dome...
• Different reed configuration...1500/1400 used 10/10 reed blocks... the later 115 came with 8/10 reed blocks ( a picture here ).
• The late 115 does have a slightly lower exhaust porting ( .020" or so ), this gave this engine some extra torque lower in the power band, but less top end hp..

And from what I have read... some of the first late 115 used the remaining 1400 blocks, when they were used..... they started withe their "new" 115 blocks ( lower exhaust ports ) .


Arne Kjetil