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Author Topic:   Montauk 170 - 4 stroke or Optimax -Help!
Captain13 posted 06-05-2004 10:01 AM ET (US)   Profile for Captain13   Send Email to Captain13  
Looking to purchase a new Montauk 170. Trying to decide between the 4 stroke or Optimax 90 which is now available. I plan to dive, fish and pull the kids on tube and skis. My dealer says get the 2 stroke because it will have much better hole shot for water sports and be as fuel efficient as the 4 strokeā€¦..

Can anyone comment on skiing with 4 stroke and thoughts on the Optimax 90 package?

Moe posted 06-05-2004 10:45 AM ET (US)     Profile for Moe  Send Email to Moe     
The 90HP Optimax is only recently available on the 170, so
there may not anyone here who has it.

This is one of those cases where the 2-stroke DFI (375 lbs)
weighs about as much as the four-stroke (386 lbs).

Using the performance data available on Whaler's website at :

With a total test weight of 2177 lbs, and a 13x19" Black Max
aluminum prop driven by 2.07:1 gearing, the 1526cc Optimax had

4.4 second time to plane and 8.6 second idle to 30 mph

With a total weight of 2207 lbs, and a 13-1/8x16" Vengeance
stainless prop driven by 2.33:1 gearing, the 1596cc 4-stroke had

4.5 second time to plane and 7.8 second idle to 30 mph

A cursory look shows the 4-stroke to be equal to or stronger than
the Optimax regarding acceleration, until you realize the 4-stroke
had the advantage of:

- 1. Lower gearing, 2.33:1 vs 2.07:1

- 2. A lower pitch prop (16") than it normally ships with (18"),
which let it overrev the 6,000 rpm limit by 200 rpm, with 2 aboard.

Had the 4-stroke had the 18" Vengeance prop it normally ships with,
its acceleration would've been slower, and it would've probably
maxxed out rpm at 5,800, 200 below its 6,000 rpm redline.

Had the Optimax had the 18" Vengeance prop the 4-stroke ships with,
its maximum rpms in this case may have been slightly above its
5750 rpm redline, and its acceleration would've been quicker.

Looking at these numbers, the Optimax "holeshot" would definitely
be better, as would its ability to pull up skiers, but I don't think
I'd say it would be "much" better. I also believe the mileage would
be about the same.

I'm a 4-stroke fan, but in this case, you can't get fuel-injection
on the 4-stroke, and I'm also a fuel-injection fan. There's a lot
to be said for the automobile-like no-choke starting, and smooth
idling of fuel-injection. There's no worry of fuel evaporating in
the system, leaving gum to clog jets.

For me, this would be a tough call. Hopefully, all the 4-stroke
owners here will weigh in with their skiing experiences.


Nushlie posted 06-05-2004 11:08 AM ET (US)     Profile for Nushlie  Send Email to Nushlie     
Captain 13:

The 2 stroke is probably a couple thousand dollars cheaper than the 4, has a little better get up and go for skiing, and I would think less routine maintenance.

The 4 stroke should be somewhat quieter, much cleaner, and may be a plus if and when you sell the boat down the road.

Either one would be fine.


Peter posted 06-05-2004 11:43 AM ET (US)     Profile for Peter  Send Email to Peter     
Unless you need a green motor, I'd go for the carbureted 2-stroke 90 instead of the Optimax or 4-stroke and save yourself quite a few bucks. It would take many years for you to recover the additional cost of either the 4-stroke or the Optimax through fuel savings.

Moe- The days of needing to use a choke to get a 2-stroke carbureted outboard started are long gone. For example, I have a carbureted Yamaha 70 2-stroke on my 15 Super Sport. To start it you simply turn the key and it starts -- first time, everytime. No throttle advance, no playing the choke switch (actually there isn't one). Idle is plenty smooth. I assume Merc must use the same technology on its conventional 2-strokes.

Maximus posted 06-05-2004 06:44 PM ET (US)     Profile for Maximus  Send Email to Maximus     
My '03 90HP 4stroke with carbs does not require a choke. Just turn the key.

Go for the 4stroke, you will love the difference: no smoke and no noise.

AQUANUT posted 06-05-2004 08:59 PM ET (US)     Profile for AQUANUT  Send Email to AQUANUT     
I have experience with both the 75/p0/115hp fourstroke and the 09/115hp optis. in running these motors I honestly see very little difference...weight is in favor of the lighter optis...but only approx 24 far as noise and smoke..they are just about the same.

75/90/115hp optis are way more quieter than the 135/150's

I am currently running a 115hp 4 stroke EFI on my 2004 montauk 170....I prefer electronic fuel injection

my second choice would be the optis DFI [dirrect fuel injection]

and last would be anything carbed [I am now on a low/no carb diet]

although the opti doesn't choke like the carbed models of the past...[its done automaticly] is usually, escpecially in cold weather conditions to use the warm up level and give the engine pleaty of time to warm up before leaving the dock!

mikeyairtime posted 06-05-2004 11:33 PM ET (US)     Profile for mikeyairtime    
Getting rid of my last 2 stroke was the best day of my life. No more buying $12 a gallon two stroke oil. Here in California two strokes kill a boats resale value, no one wants them because you can't use them on any alot of lakes. Those same rules will eventually be comming your way.
AQUANUT posted 06-06-2004 09:15 AM ET (US)     Profile for AQUANUT  Send Email to AQUANUT     
define alot of lakes...can you use 2 strokes on shasta....
clearlake.....or is it only no 2 strokes on tahoe?
Peter posted 06-06-2004 11:44 AM ET (US)     Profile for Peter  Send Email to Peter     
Interesting... if saving money on $12 oil is a motivating factor to buy a 4-stroke, then consider the following. The difference in price between the 4-stroke and the conventional 2-stroke will buy 150 gallons of $12 2-cycle oil. If oiling at a very rich 50 to 1 ratio all of the time, you would have to burn 7,500 gallons of gas to use that much oil. At a low estimate of 4 MPG in a Montauk, you would have to travel about 30,000 miles before the cost of the 2-stroke motor and oil would equal the initial cost of the 4-stroke motor. At an average of 30 MPH (a very high but mathematically simplified estimate) 30,000 miles is 1,000 hours of operation. With 50 hours being typical usage over a season, the break even point is 20 years in the future!

Look at it a different way. Assume gas is $2.50 per gallon. Assume that the 2-stroke oil adds $0.25 per gallon to make the fuel mixture consumed by the 2-stroke $2.75 and assume that you get 4-stroke oil and oil changes for free so that the cost of fuel consumed by the 4-stroke is $2.50 per gallon. Also assume that the 4-stroke gets 6 MPG on average while the 2-stroke only gets 4 MPG (real world difference is likely to be a lot less). To make up the difference in price between the two outboards, you would have to burn about 4,800 gallons of additional gas in the 2-stroke ($1,800/$0.25 = 7,200 gallons * 2/3 fuel efficient). If I have the math right, then at 4 MPG, this works out to about 19,000 miles or about 13 50 hour seasons before the initial cost is recovered.

Factor in the cost of 4-stroke oil changes, and the break even time is further in the future. If the price of gas goes down, the break even time grows longer. If the price of gas goes up, the break even time grows shorter. Of course, depreciation of the two outboards and investing the saved money wisely have not even been considered, and if they were, the break even time would grow longer and perhaps may never be reached.

If you want a 4-stroke or an Optimax, get it because you like the features as compared to a conventional 2-stroke (quiet and no smoke), but not because you think you will save money over the long run because the long run is truly very LONG.

prm1177 posted 06-06-2004 01:23 PM ET (US)     Profile for prm1177  Send Email to prm1177     
As an owner of an Outrage II 17 with an Opti 135, I have gazed longingly at the 4 stroke world. My major focus point is how amazingly quiet the new four strokes are. That said, the performance of my Opti is excellent. It sips fuel, doesn't smoke, is easy on oil consumption, and is CARB rated at 3 stars the same as most 4 strokes. As much as I would like a quieter motor, I'm keeping the Opti until it dies or until the 150 HP Verados appear. ;)
mikeyairtime posted 06-06-2004 09:10 PM ET (US)     Profile for mikeyairtime    
As for the argument about purchase price my neighbor told me the same thing when I paid the extra money for the Duramax diesel in my pickup. Now he wants one.
LHG posted 06-07-2004 01:20 PM ET (US)     Profile for LHG    
The reason the clean 90's, or any other HP range for that matter, run approximately the same (at least in the Mercury line) is that to meet the 3 star ratings, Mercury can no longer give away "free HP". Evidently, allowable emissions ratings are based on the HP output. The two stroke Merc 90 is more like 100HP. All this directly from a Mercury technical person. None of this means that it's not probable that the 2-stroke Opti's will accelerate faster, Verado's excepted.

Note that the Mercury 90 Opti and 4-stroke run approximately the same, as do the Mercury 115 Optimax and 115 4-stroke on the Nantucket. In both cases Mercury's conventional 2-strokes seem to deliver better performance

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