Mercury FourStroke 115 EFI : nothing is like it was

A comparative test between the old Mercury F115 four stroke, and the brand new EFI 115 sees the latter improving on the former in every aspect: lighter, quieter, more performing, and even better looking. We compared them in the Sicily sea, mounted on two identical Quicksilver Activ 605 Sundeck.

You see them side by side, and it’s tough to say that the new Mercury 115 has a bigger displacement than the old, being lighter and smaller at the same time. Now 2068 cc. from the previous 1732, the new unit saves weight not only on the predecessor but also on the Optimax, 2-stroke 1.5 liters. It’s the lightest in its power segment, despite the largest and the one with most roque (23% more than the old one at 3500 rpm).

All of this has been obtained through a massive simplification in design and build: four-in-line, just one camshaft, two valves, but with needle bearings to reduce grip by 15%. It’s the same path of the bigger brother Mercury 150.

Also available for this engine is a sturdier leg, called CT (command Thrust) for heavier duties and better acceleration. The standard final ratio of 2.07:1 is the best compromise for efficiency and performance, while the CT features a 2.38:1 and a larger gearbox, more suitable to harder usage such as on planing and heavy boats.


The new engine cover looks good, but it’s been designed for a better air intake, while reducing noise and vibration. The peculiar position of the throttle valve, and a noise filter on the idle exhaust further reduce the decibels, while a new trim pump is designed for more quietness as well. New silent blocks and a different design of the gearbox complete the package in order to minimize NVH. On a maintenance point of view, the new outboards have been designed with much attention to avoid corrosion : thus copper and stainless steel details, and the MercFusion varnish specifically designed to face the hardest marine environment.


Even the ordinary maintenance has been simplified: the single camshaft distribution made service intervals longer, while even installation is quicker thanks to specific parts and common platforms across the range. Finally, we remind that the new 2.1 liters is available in three power steps: 80, 100 and 115. Much likely, the latter will be the most popular.

The test boat: Quicksilver Activ 605 Sundeck

It’s a good looking boat, featuring in just 6 meters a cosy front sunbed, a cabin underneath and a cockpit that turns into a dinette by rotating the two seats. We just feel the lack of a small grill-and-sink cabinet outside, if the designer could fit that then it would be a perfect realization. Still we can appreciate the good finishing of every material and the versatility of the boat, that can offer two comfy berths, a hidden potty, and a covered dinette in case of bad weather. The helm station is simple and rational, with enough room for a GPS plotter screen, although the engine gauges give already plenty of information. What else..?

mercury-115-efi_quicksilver-605 mercury-115-efi_quicksilver-605 mercury-115-efi_quicksilver-605 mercury-115-efi_quicksilver-605

The test

We already tested the 115 EFI and the smaller 100 HP in USA, and if you want to compare the results of this test, run in far different water conditions and on rather unusual boats (for our market), you can find them on this very website at this HYPERLINK “”link. Here the sea trial is more credible in terms of absolute performance and noise figures, while we couldn’t check the actual fuel consumption of the old 115 as it didn’t feature the dedicated software: so we had to rely on the official figures from Mercury. I don’t want to spend too many words on the pleasant navigation granted by the Quicksilver Activ 605, it’s a well known boat and the calm sea outside Catania increases the good feelings of the cruise. I focus on the performance comparison, keeping in mind how the new 115 EFI mounts the CT leg: it’s a bit larger than the sleek leg of the other model, thus hindering results. It’s good to test also this version, but on such boat we’d go for the normal one. Technically, the CT has a final ratio of 2,38:1 with a Vengeance 17” three-blade propeller, while the normal leg mounted on the old 115 has a final ratio of 2,33 and a 15” prop, still from Vengeance.


The feeling during navigation is better with the new 115 EFI, much more than the numbers say; in particular the higher you rev the more you feel how quiet the new unit is, despite the action of the wind. The time to plane drops down from 5,4 to 4,5 seconds, while the progression up to maximum speed larks the same 20 seconds. Minimum planing pace is at 11 knots for both, but the new engine is revving at 3200 rpm as compared to 3800 for the old one. The former definitely wins also when measuring top speed: 32 knots at 6000 rpm towards 26,5 at 6400. When looking at fuel consumption, in liters or gallons per hour at a certain engine speed, the old 115 seems to win: but when you look at the real pace and reckon the actual liters (or gallons) per mile, you realize how the new EFI totally wins.


Technical features
Architecture     4-in-line, 4 strokes
Valves     8
Displacement     2064 cc (126 cubic inches)
Revs     5000-6000
Final ratio      (CT leg)     2.38
Price 115 EFI     € 10.700 VAT included
Price 115 EFI CT     € 10.950 VAT included

Performance new Mercury FourStroke 115 EFI
1000 rpm       3,9 knots       4.5 mph        2,2 l/h      0.6 gph     56 db
1500 rpm       5,0 knots       5.8 mph        3,7 l/h      1.0 gph     64 db
2000 rpm       6,4 knots        7.3 mph       5,7 l/h      1.5 gph     68 db
2500 rpm       6,8 knots       7.8 mph       8,3 l/h      2.2 gph     69 db
3000 rpm       8,4 knots        9.7 mph      11,1 l/h      2.9 gph     76 db
3500 rpm       11,8 knots      13.6 mph     14,8 l/h     3.9 gph     79 db
4000 rpm       17,5 knots      20.1 mph     19,0 l/h     5.0 gph     81 db
4500 rpm       22,7 knots      26.1 mph     22,8 l/h     6.0 gph     81 db
5000 rpm       26,5 knots      30.5 mph     28,0 l/h    7.4 gph     81 db
5500 rpm       29,2 knots      33.6 mph     35,1 l/h     9.3 gph     82 db
6000 rpm       32,0 knots      36.8mph     42,0 l/h      11.1 gph   84 db

Performance old Mercury FourStroke F115
1000 rpm       3,0 knots      3.5 mph       1,7 l/h        0.5 gph      59 db
1500 rpm       4,3 knots      4.9 mph         3,0 l/h       0.8 gph     62 db
2000 rpm       5,5 knots      6.3 mph        4,4 l/h       1.2 gph       66 db
2500 rpm       6,4 knots      7.4 mph         5,9 l/h       1.6 gph      68 db
3000 rpm       7,2 knots      8.3 mph        9,1 l/h        2.4 gph      77 db
3500 rpm       9,0 knots      10.4 mph      13,0 l/h      3.4 gph      83 db
4000 rpm      11,5 knots      13.2 mph      16,7 l/h       4.4 gph     87 db
4500 rpm      13,2 knots      15.2 mph       19,4 l/h     5.1 gph      89 db
5000 rpm      18,0 knots      20.7 mph     22,8 l/h     6.0 gph     86 db
5500 rpm      20,7 knots      23.8 mph      29,1 l/h     7.7 gph      83 db
6000 rpm      25,0 knots      28.8 mph     38,5 l/h     10.2 gph   86 db
6400 rpm      26,5 knots      30.5 mph      41,7 l/h     11.0 gph     88 db

Test conditions
Calm sea, temperature 28° C (82° F), fuel 40 lt (10.6 US gal) both, fresh water 0 lt, 3 passengers, clean hull

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