Need advice - 2 Stoke Optimax option

dmanmtl

Seaman
Joined
Apr 14, 2013
Messages
63
I'm looking for some opinions from the knowledgeable community on this board. I am planning to switch from my current sport boat (Bayliner 175) to something more suited to fishing which is what i do most of the time.

I have the option to buy a 2005 Legend 16.9 foot fishing boat with a 115 Mercury Optimax motor on the back. I am aware that the Optimax is a two stroke, and I know the trend recently has been towards 4-storkes for various reasons. I have researched this a lot, have a buddy with a 2 stroke Evinrude which runs great, and I can see how a 2 stroke is still a viable engine, less complicated, lighter, more torque. But I am still a little concerned about not buying a 4 stroke - not sure why.

Does anyone have any experience with the 2004 Optimax to share? Is this a reliable engine? What should I check for? any other advice?

Thanks in advance.

D
 

Chris1956

Supreme Mariner
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Mar 25, 2004
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27,036
The Optimax motor does not share a lot of technology with a carb'd 2 cycle outboard. Sure they both operate on the two-cycle power principle, but that is about it. Optimax uses compressed air to force gasoline into the combustion chamber, after the transfer and exhaust ports are closed. Oil lubricates the bearings and rings. The result is a very clean running motor, that uses very little oil, in comparison to a conventional 50::1 fuel mix as in your friend's Evinrude.

I do not think you will find much difference between Optimax and a modern 4 cycle OB motor, in terms of fuel economy, weight, complexity or power.

IMO, Optimax is just as complex as a modern 4 cycle fuel injected outboard.
 

dmanmtl

Seaman
Joined
Apr 14, 2013
Messages
63
Chris - thanks for your reply. Do you have any insights on the reliability of these motors? The one I am looking at is 12 years old, but apparently low hours (to be confirmed)

Also, I am familiar with how a conventional 2 stroke works, whereby the gas/oil mixture lubricates the bearings etc, but in the case of these (would you call them direct injection?) engines how does oil get to the vital parts like the crankshaft if the mixture is injected into the cylinder?

Thanks again for sharing your knowledge
D
 

Chris1956

Supreme Mariner
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Mar 25, 2004
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27,036
I cannot comment on the reliability of the Optimax versus a 4 cycle motor. I would expect them to be roughly the same. I do expect the Optimax (and E-Tec) motors to be phased out in the future (my opinion only), because in my opinion, they have no real advantage over a 4 cycle motor, and 4 cycle motors can adapt technology from the automotive world, which Optimax cannot.

On the Optimax, only gasoline is injected into the combustion chamber. The V6 Optimax has a 7 port oil pump that pumps oil into each cylinder, plus the compressor.
 

Faztbullet

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Mar 2, 2008
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15,589
Di engines are here to stay as (1)they are lighter, (2)less moving parts to maintain,and able to use heavy fuel as jet fuel (Jet A, JP5, JP8).Carb and EFI cannot. This is why military has went to these engine as no need to carry gasoline. For everyday use a 4 stroke is ok but find a 08 or newer if you go DI
 

Chris1956

Supreme Mariner
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Mar 25, 2004
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27,036
Fazt, Are those heavy fuel Optimax OBs available to the commercial public, or are they military-only? Are they truly multi-fuel, or are the heavy fuel Optimax's only capable of running Kerosene and Diesel?
 

ajgraz

Lieutenant Commander
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Mar 1, 2010
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1,858
A buddy at work tells me that DFI 2-stroke is all the rage in dirt bikes these days, too. I think it'll be around awhile. And I fall into the camp that says yes, Optimax is more complex than old 2-stroke, but still WAY less complex/intricate than any 4-stroke OB.

Here's what I can tell you about the 2012 Optimax 125 on my 17' CC vs the late-70's 3-cyl 70hp (probably 50hp by today's standards) Merc on my old 15' trihull:
The Opti pushes 50% more weight 60% faster using 40% less fuel, uses a heckuva lot less 2-stroke oil, and is many orders of magnitude less polluting. And quieter!

EDIT: also it is my understanding, though I cannot point you to a DEFINITE source on this other than a lot of forum hearsay, that the Optimax high-pressure air pump technology was kinda "iffy" up until 2004, but became much better 2005 and after.
 
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