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Author Topic:   115hp Merc EFI 4 Stroke vs 135hp Optimax
Clark Roberts posted 02-06-2002 06:47 PM ET (US)   Profile for Clark Roberts   Send Email to Clark Roberts  
I just finished breaking in a new 115 Merc EFI 4 Stroker haveing traded in a 2000 135 Optimax. The 5 yr warranty snagged me as I was due for extended warranty purchase on the Opti. In any case I like the 4 stroke and it has plenty of power for the way I use my 1979 Revenge 21... The Opti was great with fantastic mileage but couldn't use all the power. Here are the performance comparison figures rounded a little to get the decimals out. Gross weight of the rig with Opti is around 3100lbs and around 3000lbs for the 4 stroker..... 3500rpm> Opti=25mph/4stroker=20mph; 4000rpm> 30/25; 4500rpm> 35/30; 5000rpm> 40/35; 5500rpm> 45/38; 5900rpm for the 4stroker = 40mph. The lower unit ratio on the Opti is 2:1 and 2.06:1 for the 4 stroker... 19" pitch Quicksilver Vengence ss prop on Opti and 15" pitch Stilletto on the 4 stroker.. Opti had a manual T&H Jack plate up about 3" and the 4 stroker has a power jack plate by Bob's Machine and will run up 4" (watching water press meter... no loss, steady at 20psi at WOT... etc,,,etc,,,, etc,,,, will report fuel mileage comparison later... The Opti got overall 5mpg and 6.2mpg at 28mph steady cruise so the 4 stroker has to be really good to beat it... heck, I'll be happy is it just comes close 'cause with an 80 gal. fuel capacity (40 under the deck and 20 each for the saddle tanks) I can run hard for 2 days without needing to take on fuel... will be interesting! Sweet spot cruise was 30 for the Opti and seems like around 25mph for the 4 Stroker... just right for me! Don't mean to bore you with this stuff but it could be useful to some. Happy Whalin.. Clark... Trivia Div. of Spruce Creek Navy
captreils posted 02-06-2002 07:29 PM ET (US)     Profile for captreils  Send Email to captreils     
the 135 opti is the most fuel efficient optimax merc makes,but you should see better fuel economy with the 115.even if they are the same at least you don't have to buy two cycle oil any more. especially since now merc wants you to use their synthetic optimax oil,big bucks
wildeone posted 02-07-2002 09:40 AM ET (US)     Profile for wildeone  Send Email to wildeone     
Clark, What is the cost difference (list price if you don't want to tell) between the two. I am looking to repower a 18 Outrage, and your gross weight looks comparable to mine (with my 150). I don't think I would need another 150, and enjoy seeing your comparisons on the 115 v 135.
Clark Roberts posted 02-07-2002 11:52 AM ET (US)     Profile for Clark Roberts  Send Email to Clark Roberts     
Wildeone, I don't mind telling prices... the 115 cost me 7000 plus 6.5%sales tax for a total of $7,455 (from my local Merc dealer from whom I have bought many engines ... so he treats me right!). Already had the prop and I added a water press gauge for $62. Bought motor in the box and mounted it myself... I find that I take time and care and would rather do it myself... anyway, I can screw it up for free so why pay somebody to do it!? Opti is for sale for $5900 (good deal for buyer with factory warranty until late Aug) so difference approx $1500. Cost of 2 yr extended warranty from Merc is $1700 so for $200 I have a 2002 engine with 5 yr warranty instead of a 3 yr old motor with a 2 yr warranty.... one comparison is that the mid-range power on the 115 is pretty flat whereas the 135 mid-range is explosive! But then the 115 is a 106 cubic inch engine compared to the 153 cubic inch 135hp... really comparing apples and oranges here... but the 115 accelleration is quite good and speeds are better than I expected for an engine of this size.. and wow, is it quiet. I love it! ("never become emotionally attached to an inanimate object"- whoever made that quote/advice never owned a Whaler.. heh, heh..)Happy Whalin'.. Clark.. Product Testing Div. of Spruce Creek Navy
Clark Roberts posted 02-09-2002 04:51 PM ET (US)     Profile for Clark Roberts  Send Email to Clark Roberts     
Just did a fuel mileage test on the 115 four stoker... each was with a measured gallon of fuel and included several stops/plane outs etc... Air temp at 76 degrees and water temp at 70 degrees... 40 gals of fuel aboard..>> 4000rpm/25mpy got 5.3mpg : 4200rpm/27mph got 5.5mpg : 4500rpm/30mph got 5.0mpg.. not as good as the Optimax but maybe when I have some more hrs. it will improve... I'm happy with it as is , however! Later on I will check mileage on a cruise of several hundred miles... that overall average is what counts! Later... happy Whalin'... Clark... Spruce Creek Navy
PS>distance was logged via gps
lhg posted 02-11-2002 03:39 PM ET (US)     Profile for lhg    
Clark, another point of interest would be the mileage the Revenge got with the conventional Merc 90 2-stroke. You seem to be one of the few who can compare all three technologies on the same hull.
Whaletosh posted 02-11-2002 04:54 PM ET (US)     Profile for Whaletosh    

Welcome to the EFI 4 stoke world. I only have 2 hours on my 60 HP EFI Merc. Even with that little I can tell that I am going to love the motor. I top out at 35-36 MPH, cruise is at 25 MPH (just right for me also). Starts like a modern car, turn the key and it starts.

Clark Roberts posted 02-11-2002 06:02 PM ET (US)     Profile for Clark Roberts  Send Email to Clark Roberts     
Larry, as I recall (and I put hundreds and hundreds of miles on with the 84 cubic inch 90 Merc) the overall mileage would have been around 3mpg max... top speed was 35mph at 5500rpm... I never made any mileage tests when I had the 200 hp Merc (carb) but it most likey got 1.5 - 2 mpg (an EFI 200 merc like yours would most likely do lots better than that)
... it did however run in the high 50's for top speed and that's way to fast for this old shucker! I like to be able to cruise at 25mph and have the capability of 30mph cruise and the 115 fits the bill... the 135 opti was very , very fast and would cruise at 40 all day long... but then now I have a 5 yr warranty... I plan to put lots of miles and hours on this one! Happy Whalin'.. Clark.. Spruce Creek Navy
lhg posted 02-11-2002 06:30 PM ET (US)     Profile for lhg    
Thanks for the info, Clark. I actually would have thought the 90 would have done better.

Looks like the newer EFI/DFI technologies really do pay. The 135 Opti is still the most amazing, considering it's a V-6 vs the 4 cylinder 4-stroke. Maybe Merc's advertizing isn't all hot air afterall.

There's also starting to be some evidence that the DFI's are outperforming the new 225 4-strokes.

Clark Roberts posted 02-12-2002 07:31 AM ET (US)     Profile for Clark Roberts  Send Email to Clark Roberts     
Larry, yes, the 135 Opti is an amazing combo of performance and economy and were it not for the 5 yr. warranty deal I would not have traded! As to the 90hp mileage, I didn't make runs on measured gallons at fixed rpms but made one particularly hard/upstream run from Apalachicola to Chattahoochee on Fla's Apalachicola river of 105 miles and used 35 gals (full 40 gal tank at start/top off at finish) which is 3mpg. This was steady cruise at 4400rpm/25mph (if I recall correctly) and I was very aware of fuel useage as there were no fuel stops along the way and 40 gals is all I had aboard. My 6 gal reserve tank had ruptured and I was sweating out making it to Chattahoochee were I was to meet my wife, Sonia, with trailer. The direct reading gauge read dead empty for the last 20 miles and I had no way to manually check fuel level (other than to take tank sensor out and use a stick). So I just kept going and kept checking cell phone for coverage... none at all along the way... So here I had planned an easy trip but didn't figure on the current being so swift (very low water) and didn't know that my aux tank was empty (it has leaked out and out the rear drain hole at sometime... who knows?) .. Anyway, after I found that I had only 5 gals left (most likey 2-3 gals useable) I set out to put in some permanent saddle tanks and now have two 20 gal saddle tanks with guages on all 3 tanks and a transfer switch.. Overkill? Not for me! And fuel mileage does matter, especially when there are 150 miles between fuel stops... Long winded this morning... Happy Whalin' .. Clark .. Spruce Creek Navy
Bigshot posted 02-12-2002 09:18 AM ET (US)     Profile for Bigshot  Send Email to Bigshot     
You were running it hard Clark. You will be amazed at the MPG in the future. Maybe not much better than your 135 but the lack of noise is soooo coool.
Richard Quinlivan posted 02-13-2002 09:40 PM ET (US)     Profile for Richard Quinlivan  Send Email to Richard Quinlivan     

I wonder if you have any feel as to the relative power of the 115 HP 4 stroke and the Merc 125 HP 2 stroke?

Dick Quinlivan

Clark Roberts posted 02-14-2002 09:07 AM ET (US)     Profile for Clark Roberts  Send Email to Clark Roberts     
Dick, power is power no matter if produced by a steam engine or a hampster in a cage. The 125 is more powerful than the 115 but the main difference is the way these engines put out their power. The two stroke has a burst of power in the mid range (around 4500rpm) and the 4 stroker power comes on smooth and steady right up to the 6000rpm redline (the 125 is rated at 5250max rpm). The 2 stroker has twice as many power stokes per rev than the 4 stroker so they sound and feel different! Engines are similar in that each has four cyls, weigh approx the same, and are of approx same displacement (106 cubes for the 115 and 113 cubes for the 125, if I recall correctly) so comparisons of two vs 4 stroke can be made (It would be a better comparison to the 115hp version of the 100/115/125hp engines). Only a side by side performance comparison would tell for sure but I can make some guesses. The 2 stroker will out perform the 4 stroker in accelleration and maybe top speed due to additional 10hp and two stroke characterstics and the 4 stroke will bet far better mileage (maybe more than twice) and will be much quieter at idle and somewhat quieter at speed. Also the 4 stroker has many, many more moving parts... reliability???? Depends on care and feeding most likely!!! Oh yes, since the 125 idles on only 2 cyls the 4 stroker lacks that "punch in the rear" of the other two cyls kicking in at about 1800 rpm when the high speed jets take over! Additionally the 115 is direct port fuel injected and has "turn key starting/auto idle" features which is so nice! More than you asked for but then I never seem to know when to stop... others may have different opinions but that's my story and I'm sticking to it... happy Whalin'.. Clark.. Spruce Creek Navy
Richard Quinlivan posted 02-14-2002 11:13 AM ET (US)     Profile for Richard Quinlivan  Send Email to Richard Quinlivan     
I know that horsepower is horsepower but I considering the rating game the manufacturers play with their 10% slop I wondered if you had any feel as to what the real horsepower of each was.
Clark Roberts posted 02-14-2002 06:38 PM ET (US)     Profile for Clark Roberts  Send Email to Clark Roberts     
Richard, my experience with the 125 Merc (on my brother-in-law's ski boat) is that his seemed to put out more than I expected for a 125hp rated engine. It really lit up and was propped for the power side and would hit 5250rpm almost instantly. My 115 EFI 4 stroker seems to put out 115 honest hp. But then, all engines are not created equal and may vary (I've heard maybe 10% either way) in actual hp even if on the same assembly run! Don't know if this is actually true but it may be so go figure. Some engines need fine tweaking out of the box to assure actual full throttle (linkage adjustments) and the correct prop/set-up/mounting height/fuel delivery system etc.. are all necessary to take full advantage of the power. I'm a fiddler and tweaker and can never leave anything alone... guess I'll never change... it's too late anyway.. happy Whalin',,, Clark.. Spruce Creek Navy

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