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Author Topic:   135 Optimax to 115 EFI 4 stroker(answer to Chris)
Clark Roberts posted 05-03-2002 03:24 PM ET (US)   Profile for Clark Roberts   Send Email to Clark Roberts  
I replaced a 2000 Opti 135 with a 115EFI four stroker Merc on my 1979 Revenge 21. This I did, not because of a problem with the Opti (it ran flawlessly for over 250hrs) but because of the 5 yr warranty incentive on the 115. It was time to buy extended warranty on the 135 and it was same money to trade for the 115... hence a new motor with 5 yr factory warranyt vs a two yr. old motor with 3 yr extended warranty... a no brainer for me since speed limits are very restrictive here in NE Fla. and I could never use all the power of the Opti! That aside, Chris asked me what I gave up in the switch so here goes! Performance is less with the 115, naturally, top speed from 45mpg to 40 and fuel mileage dropped from 5.5mpg at optimum cruise (28mph Opti) to 5.0mpg at optimum cruise (25mph 4 stroker). The 4 stroker is working harder and the Opti just loafed at cruise.Both engines are rated 3 star for emissions (Yamaha's version of the 115EFI is rated at two stars... Merc's ECM must be the difference!?). The Opti was much quicker out of the hole due to its 153 cubic inches vs. the 4 strokers 106 cubic inches.... just what I expected. Mid range is also slower and flatter than the opti.. again to be expected. The 115 is much quieter at idle and slow speeds ... the Opti injectors made a click/clack at idle. However, at speed the 4 stroker is no quieter than the Opti.. This I find true with other 4 strokers like the Yamaha 50 (on a neighbors boat)... very quiet at idle but not so quiet at speed. The 115 is about 60 lbs lighter and has a 35 ampere alternator vs the 60ampere for the opti. The 115 is much less cluttered under the cowling and spark plugs are a breeze to replace and not $20 each like the Opti... wow...!!!! Like I said, I traded for $ reasons and am happy as a clam with the four stroker. I don't miss the explosive performance of the Opti. but if performance is the goal.. go for the 135 or 150hp Opti. I look forward to many (at least 5 heh, heh) years of good service from the 4 stroker and can highly recommend it! That's about it... hope that answers your question, Chris! Happy Whalin'... Clark... Spruce Creek Navy
InHerNet posted 05-03-2002 04:56 PM ET (US)     Profile for InHerNet  Send Email to InHerNet     
Clark - This is very informative since I have two 2000 135 opti's. I recall somewhere you or someone else was discussing the trade off difference between the warranty and ordering a new motor. I know that the 4 strokes are quiet in idle and thought that they would be as quiet at full till. I know that the $20.00 each price tag on the spark plugs about floored me when I saw the bill. Take that times 12 (ouch). I elected not to purchase the extended warranty only due to my background knowledge of the warranty industry as a whole. I would rather pay for the repair or replacement if needed. Speaking of replacement! Is the 135 for sale?
lhg posted 05-03-2002 09:44 PM ET (US)     Profile for lhg    
What I think is the most interesting of Clark's data is the fuel mileage. The much bigger block V-6 Optimax gets better mileage, at higher speed, with better performance, than the 4-stroke lower HP engine. By all measures, that should not be.

Maybe there's a great future for the DFI's afterall. I also know that this 135 Opti oputperforms the Honda 130 in all categories also.

I have also noticed that the 4-strokes are no more quiet at speed than the 2-strokes.

CHenry posted 05-03-2002 10:22 PM ET (US)     Profile for CHenry  Send Email to CHenry     
Wow...some very good & surprising info (fuel & noise). You've just made my decision that much harder...but thank you...this type of first hand info can't be found in a showroom...I appreciate you taking the time to post in detail.

I still don't know what I'm going to do but at least I have the info I need to make a more informed decision.


Clark Roberts posted 05-04-2002 12:28 AM ET (US)     Profile for Clark Roberts  Send Email to Clark Roberts     
My mileage figures are based on long steady cruises of a hundred miles or more and could be off by maybe 10 %. Therefore the engines get basically the same mileage.. as Larry said, the opti gets it at a faster cruise speed... 25mph seems to be ideal for the 115 but with a little less than 100 hrs on the clock, performance and mileage on the 115 may improve with some more running time and oil change! The strong point of the 115 is smooth, effortless running of the many miles of slow/idle speed zones with which we are plagued. It just plugs away like a Maine lobster boat and never misses a beat. The Opti, and most two strokers balk and stumble at times (some older two strokers foul plugs) and seem to complain about the prolonged idle speeds. I installed an oil press gauge on the 115 (just couldn't stand not knowing) and it runs 50 to 60 psi at idle and 85 to 95 at speed. I'm running a 15" pitch Stilletto prop an she will hit 5900 when trimmed out and jacked up 3 1/2 inches via Bob's Machine hyd jack plate. Water press holds at around 20 psi... no problems! Etc..etc.. blah,,, blah,,blah.. will stop for now! Happy Whalin'... Clark.. Spruce Creek Navy
tabasco posted 05-06-2002 08:56 AM ET (US)     Profile for tabasco  Send Email to tabasco     
Some where I missed what model boat you did your installation. Would appreciate knowing....thanks


tabasco posted 05-06-2002 08:58 AM ET (US)     Profile for tabasco  Send Email to tabasco     
OK I just had my coffee and see that it was a Revenge 21 ......thanks for the input
isotope posted 04-11-2003 02:09 AM ET (US)     Profile for isotope  Send Email to isotope     
another opinion on the opti vs 4
i dont own a whaler, but did just upgrade the 50hp 2 stroke on my 16' avenger sport.
originally i was planning on a 90 four stroke, which was the max hp/weight recomended. it is common knowledge that 2 strokes from a performance aspect generally outgun the four's. this could be due to the lighter weight and better power band for 2strokes. upon further research it does appear that the new direct injection 2 strokes (ficht & opti) do get better fuel milage. there is the noise issue, while comperable at high speed on the demo boats, the injectors were noticable at idle on the 2 stroke, while i had to check the 4 at idle to make sure it was running.
in the end i found the 115 opti weighed 11lbs less than the 90 4 stroke. from the merc. specs fuel consumption is comperable for the 2 engines, even with the larger displacement and hp on the opti.
so now my 16' aluminum fisher avenger has a sweet lil 115 opti on it... and man does it fly...but thats another story...
lhg posted 04-11-2003 02:16 PM ET (US)     Profile for lhg    
Is that the brand new 1.5 liter, 3 cylinder Optimax 115, or one of the V-6 115's?
BWdaunt18 posted 04-16-2003 05:11 PM ET (US)     Profile for BWdaunt18  Send Email to BWdaunt18     
I have a 2001 135 opti on a Dauntless 18. With two persons and full fuel, I get about 42 MPH at WOT. About 5300 RPM. Standard SS prop.

It seems like I should get a little more speed.


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