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4 stroke Yami takes on an Optimax

G

galamb

Silver Medal Contributor
"Performance comparisons betwe

"Performance comparisons between a direct injected 200 horse 2 stroke and a 4 stroke.

I just picked up some recently published tests. They compared a 200 horse 4 stroke Yami and 200 horse DFI 2 stroke Optimax.

The motors were mounted on new Wellcraft 21 footers of similar dry weight/rigging. The one noticable difference was the amount of fuel on board. The Yami kitted boat had 25 gallons in the tank, the Merc about 70 (or approx 300 pounds more weight).

So not a perfectly scientific comparison, but some "real life" tests.

The conclusions - the Opti's top speed (even with 300 extra pounds on board) is a little faster than the Yami (about 2 mph) but it burns 3 more gph at top end.

However, when you compare apples to apples, at 42.4/43.9 mph they burn 17.4/17.0 gph each (the Opti is a touch slower, but put 2 more adults on the Yami (or 300 pounds of fuel) and see what happens.

Best cruise speed/gph/mpg

Yami - 26.2 mph @ 4000 rpms burning 8.1 gph (3.23 mpg)

Opti - 32.2 mph @ 4000 rpms burning 10.8 gph (2.99 mpg)

The Yami would have to run at little above 4500 rpms to keep up with the Merc, and guess what, would burn a little over 10 gph - or alternately, the Opti could slow down to the Yami's cruise speed, but would still burn 9.4 gph (or about 16% more fuel).

What did surprise me a little was the hole shot - the Yami got the boat on plane .1 sec quicker than the Merc (again though, the extra weight probably played in a bit) - but what surprised me even more was the fact that the Yami took 2 extra seconds (9 vs 7) to get to 30 mph - that's close to 25% slower even though it planed out at about the same time (strange), would have expected the "band" to be quite similar once both motors were up and going...

Anyhow, here's the actual results - first the Yami...

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I'm not surprised about th

I'm not surprised about the hole shot. Most of the guys around here say that the 4's do get up on plane quicker than the 2's...the 2's develop their hp further up in the rev's. I do think the fuel consumption rates with the bigger engines is close between the 2's and 4's. But Graham even thou I still run a carbed 2 stroke and like it...common sense tells me that the 4 stroke oilpan helps protect from what has happened to every 2 stroke I've owned. A dry cylinder or water penatration (for various reasons)leading to a major failure. In the past 6 or 7 years I'm seeing for the first time guides trading in their used (running) 4's for new 4's. In the past they (and me) bought new 2's because our old 2's blew up...forcing us into new purchases. I've gotten a consistent 5 seasons out of the last 3 powerheads (2 stroke) with about 900 total hrs on each. I unlike most I maintain my engines properly too and don't run it hard...4200 rpm's is my prefered cruise.
 
"I wonder how long the bearing

"I wonder how long the bearings in those 4 strokes will last after running at 4,000 rpms for extended periods? No problem for the 2 strokes, however. Also, let us not forget, most 4 stroke outboards have a longer stroke, narrower bore, which only accentuates their already high piston speeds.

Jeff"
 
"And to be fair here too, this

"And to be fair here too, this Opti was put up against a Yamaha. Yami's fuel economy and performance is right at the top of the scale.

It would be nice to see the same comparison done between different 4 stroke mfgs.

Just from other tests I have seen I do not believe that Honda or Suzuki (or even Mercs 4 stroke line) would fair as well (although personally still think Honda is the best built 4 stroke on the market from a mechanical point of view and would buy a Honda over all others).

Yes, I'm a 2 stroke supporter, but what I do like about these tests is that they disprove alot of the "myth and hype".

One example is "how quiet" the motor is. Check out the last column in the charts - that's DB readings in the cockpit. Ok, yes, at 500 rpms the Yami is nice and quiet, but compare them line by line after that. The "NON-4STROKE" model is not exactly an "ear bleeder"..."
 
"Thanks for the test results .

"Thanks for the test results .
I was talking to some ski race guys who have gone to a Suzuki DF250ss from a Merc 250 xs and say the Suzuki is only 4 mph slower ,plus they say suzuki have a 400hp 4 Stroke in the wings ??.
Given their understressed design i dont see a probelm with 4000 rpm .Last year I saw a commercial DF 250 with 5000 hours on it .Happy Days !!!"
 
"Ya, we really need a 400 hors

"Ya, we really need a 400 horse outboard


Have seen Yami's 350 horse, 5.7 litre V8 up close.

And yes, if you can hang 850 pounds (without the oil or prop) of motor off the back of your rig and lighten your wallet by the 35K (MSRP) you too can have bookends - with your outboard and the motor in your tow vehicle being "matched"


But why stop at a single - go for twins - can't remember what they were hangin' on (maybe a 35' Grady) but here's the numbers.

And really, if you can spring nearly 70K for a pair of motors, what's the big deal if they burn about 68 gph....

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"Of course we need 400hp 4 str

"Of course we need 400hp 4 strokes
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Based on the DF 300 ,604lbs it will be a lightweight .

It doesnt stop at twins there is a you tube Rib somewhere my kids showed me with 4 DF 300s ,going to be used as a dive boat somewhere, 45ft ,48knts as i said Happy days
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"I saw a boat with THREE Yamah

"I saw a boat with THREE Yamaha 350 hp motors on it--and it wasn't a drug smuggler's rig, either. Somebody's got the juice!

Jeff"
 
"It doesnt stop there , Miami

"It doesnt stop there , Miami Boat show 5 ,350 Verados on a Centre console ,they were 350 stickers ??.Pictures are on Freeze Frame .

Money is a tomporary inconvience"
 
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