1984 115 inline 6,1984 90 inline 6 differnce

[caldog101]

Hi everybody
I own a 1984 mercury 115 hp inline 6 that i use for parts, and my buddy just got a 1984 mariner 90 hp inline 6 that is in fantastic shape i was wondering if we take the carbs off the 115 and put them on the 90 if it will work the motors look identical except for the color thanks

 

[Droll]

Re: 1984 115 inline 6,1984 90 inline 6 differnce

Hi everybody
I own a 1984 mercury 115 hp inline 6 that i use for parts, and my buddy just got a 1984 mariner 90 hp inline 6 that is in fantastic shape i was wondering if we take the carbs off the 115 and put them on the 90 if it will work the motors look identical except for the color thanks

It might work BUT you will have to switch main jets, the jets on the 115 hp are to big for the 90.

But it will be better to remove the 90 carbs and give them a good cleaning/tuning + purchase 3 carb kits .

Arne Kjetil

 

[Laddies]

Re: 1984 115 inline 6,1984 90 inline 6 differnce

The 90 and 115 HP engines have a different port timing, if you doubt it try to run the 90 up to the 5500 or more that you can a 115 and it will fall on it's face. To rejet or change carbs you can simply burn more fuel.

 

[caldog101]

Re: 1984 115 inline 6,1984 90 inline 6 differnce

thanks laddies ,we were thinking of putting on the complete carbs off the 115 not just the jets,my buddy is going to get the carb kit ,but he mentioned my 115 carbs on his 90 do you think he will get more hp out off it or will he just burn more fuel also was wondering if it will do any harm thanks again

 

[Droll]

Re: 1984 115 inline 6,1984 90 inline 6 differnce

It will run with the 115 carbs, but it will probably use more fuel, be hard to get a god idle, and no performance gain.

Have been used somewhere around 40 different carbs on the inline 6 engines between 1972 and 1988, not necessary big differences but.....

Don't mix/match parts without knowing what you are doing, or at least be willing to accept the risks .

The 115 basically got the same port map as the earlier 150/140 hp engine ( crank rated), it was tuned down to 115 hp ( at the prop ) by a different reed setup/ low dome pistons/slightly lowered porting.

The 90 got very small ports, NO power ports ( 115 got power ports), same reedblocks as the early 115/150/140, BUT with different reeds ( reed shape ).

Most of the parts can be swapt between those engines, except for :

• Blocks ( differen porting)
• Carburetors( jets, shutter holes ++ )
• Pistons from the 115 can be used on the 90, but not the other way ( unless switching ALL ( less performance ), ALL 6 should be the same type .
• Reed blocks from the 90 can be used on the 115 ( with possible performance gain IF switching reeds ), using the 115 reed block on the 90 will give less performance..

Crankshaft/rods/ignition parts/lower unit/leg +++ are the same on bout engines.

Arne Kjetil

 

[caldog101]

Re: 1984 115 inline 6,1984 90 inline 6 differnce

Thanks DRoll for all the helpfull info ,i guess we won't be swapping the carbs but all the other info about these motors has been great I really appreciate it one more ? i have the same motor 1984 115 hp inline 6 "the other one i got real cheap as a spare parts motor" it's on my 1976 20 foot seacraft and it pushes it about 41 mph at about 5350 rpms top speed is this motor really a 140 hp the lower unit ? i heard in 1984 or 85 they changed the rating form powerhead to prop

 

[Droll]

Re: 1984 115 inline 6,1984 90 inline 6 differnce

is this motor really a 140 hp the lower unit ? i heard in 1984 or 85 they changed the rating form powerhead to prop

The 150/140 hp engine were rated at the crankshaft.
The later 115 ( 1983 > 1988 ) uses the same block, but are slightly detuned....it got slightly lowered porting/ Low dome pistons/ 10/8 reedblock and is rated at the prop shaft.

And before you ask...

Top reed block are used on the 150/140 hp engine ( 10 pedals up/10 pedals down )
Lower reed block are used on the later 115 hp ( 10 pedals up /8 pedals down ) .

The later 115 can be converted to 150/140 hp spec by

• Replacing all pistons with high dome power port pistons ( as used on the early 150 hp ).
• Replace all 3 reed block with 150/140 hp 10/10 blocks, WITH banjo reeds.
• Replace all 3 carb with 150/140 hp carbs.

You will then have close to ?? 145 hp at the crankshaft or 125/130 at the propshaft ( estimated hp numbers )

And why I am using "150/140 hp"......only difference were the decals.

Arne Kjetil