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  1. #1
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    The Best Merc Tower

    Does anyone know which tower in-line 6 motor put out the most power, the 1980 Mercury 140 hp, or the 1988 Mercury 115? It seems to me that the 140 would have an edge over the 115 in this scenario since it should be about 122 hp at the prop (140*0.875) = 122.5, using the 10 to 15 percent estimated drop from powerhead to prop rating [(15+10)/2]=12.5%, I truncated the decimal for the final output (122.5 to 122 hp).

  2. #2
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    Neither, the 1500XS put out the most power.

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  4. #3
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    One w/out a burnt piston.

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  6. #4
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    Indeed, Mercury claimed 155 hp at the power head. However, that motor just isn't practical in most applications due to the 15" mid section. Good for race boats, not good for most 20" transoms. So I am curious about the later ADI tower motors, which of those were the most powerful. The 1980 140 hp motor was the first model year run for solid state ignition with that high hp rating. Then it disappeared altogether in 1981. I keep hearing stories about how the prop rated 115's were the same as the 140 hp. That is quite possible since it's prop rating should be 122 hp (see my first post). I figured someone here may have worked for Mercury and could clear that up. BTW: I don't believe the similar notion that the power head rated 115 hp became the prop rated 90 hp. The prop rated 90 was only rated at 5000 rpm max. I'm guessing that was do to restricted intake ports on the 90. I would be very surprised to hear a Mercury person say that is the same motor.

  7. #5
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    The latest 90 hp motors had VERY small ports......smaller than the old 115s had. The best L6 is the later 115s.... they got better salt water paint and newer trim systems..... and can be bought for a nice price if ya look around.

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  9. #6
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    1980 140hp and 1988 115 have the same crankshaft h.p. which is 150h.p., same as the 150s from 73 thru 77. in 78 merc took the 1500 and put 1400 decals on them because of having a 150 v-6, in 82 the 140 became the last generation 115.

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  11. #7
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    Yep......1500XS.........inlines began a downhill slide in 1976/1977. Squeezed by the 850 from below and V6s from above. Kinda reborn again many years later in the Verado line.

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