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Old 26 February 2014, 16:24   #11
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Quote:
Good post but a 1995 2s vs 2011 4s isn't a fair test.
I concur completely with this statement. However, this is the real world and that's the engines i had purchased. In a perfect world, it would have been awesome to test brand new engines against each other............

If this had been a test between the older 40hp carb model honda, from the same era, i have no doubt that the results would have been COMPLETELY different!! (i actually have 2x50hp carb model Honda's on my 18' cat and they are a bit sluggish out of the hole, even with low pitched semi-cleaver props on)

Quote:
2s tech has come on leaps and bounds too!!
Yes and No on this point. In South Africa, Yamaha has decided to drop the 3 cylinder 40hp 2 stroke yamaha from it's range and now only offer a 2 cylinder single carb 40hp 2 stroke. Bulletproof engines, made for hardcore, middle of nowhere use. Heavy on fuel, but VERY reliable. The technology on the yamaha smaller class 2 strokes, ie. sub 100hp is pretty much the same as it was 15 years ago. Why mess with a winning recipe? hahahaha

Other manufacturers like Evinrude ETEC do offer direct injection on their smaller motors. Unfortunately, these motors are not popular here and i actually don't know of a single one of my friends who have them on their boats.

We unfortunately only get a few models of Tohatsu 2 stroke, carb models, so there isn't much new 2 stroke technology in our country to compare the 4 stroke to.

Quote:
As I've said before, I love my Honda 50. I was aware of the BLAST technology, though was a little sceptical as to how well it would work, but must admit that it seems to jump onto the plane when you whack the throttle open, and the fuel economy is exceptional.
I also read about BLAST and LEAN BURN. All the modern manufacturers have some sort of new name, which the advertsing guys push hard. It usually take it with a pinch of salt and dont believe everything i'm told. In this case, the BLAST certainly does work!! It would be very interesting to test a 4 stroke, like say a 40hp Suzuki or Yamaha which does not have blast, just to see what the difference really is......

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PS. When you do the re-test, will you leave sleepy-head ashore so the only weight difference is the engine/battery?
I will do even better!! I will get my buddy who did the first test with me to tag along. Unfortunately, he was spearfishing up the coast off his rib, so he wasn't available.

In theory, since the motor uses almost 50% less fuel, it means that theoretically i can carry 50% less fuel. Not a major saving in weight, but it will be close enough to offset the weight of the battery. Then the only difference is the physical weight between the two engines, which is 22kg's..........

Just for interest sake, sleepy head was 5 months old when she went 30nm offshore with me on my big boat.......... Besides, all the boats i own ACTUALLY belongs to HER!!











Quote:
Brilliant test but agree with HP .. It s not a fair test.. I dont mean that in a bad way so appologies i it came over like that.. Fantastic detail and effort!
I would like to see a test on a like for like set up.. A big well done for doing it!!
As mentioned above, i COMPLETELY agree, but it's what i had at my disposal. I've been thinking about this type of test for a while and there are just soooooo many variables that i didn't take into account:
- the yamaha has a 12p prop, the honda a 13p. BUT, the Honda comes standard with a semi-cleaver prop, the yamaha not.
- even if both motors have the same size props on, the gearbox ratios are different, which would skew the results.

There is a few GENERALLY accepted facts that i've come to find to be completely inaccurate. Take my old 6.5m Hysucat for example. It was powered by 2x50hp Yamaha carb model 4 strokes. Boat was 2 years old when i bought her. Did 33knots top speed, whether boat was empty or had 600kg+ of fish and 4 crew onboard. My buddy had a 6.5m Mako rib, which was actually a copy of the PHANTOM hull from your side of the world. He also had 2x50hp 4 stroke carb model Yamaha's, but his motors had probably 2000hours+ on them. We would run out to our tuna grounds together and fish/spearfish together, so our trips were almost identical. Usual cruising speed was 18-20knots. According to the Hysucat marketing guys, it's a cat AND has foils, so it would be X% lighter on fuel than a comparable monohull rib of similar size. In reality, i was 30% HEAVIER on fuel than my buddy on his monohull!! Finally figured out that my motors had to work too hard to keep the boat on the foils, which meant i was running at higher rpm's than my buddy, hence the heavier fuel bill............

Anycase, i digress too much!!

6.5m Hysucat and Mako(Phantom):








ps. My next step is that i want to test various props on my rig, and see what the real world differences is. ie. 3 blade vs 4 blade. Standard vs semi-cleaver vs cleaver. Allum. vs Stainless. Trying to keep in mind what your AVERAGE boater is looking for, ie. not just top end speed, but rather comfortable cruising speed and economy. (this idea was bred by my local Yamaha dealer)
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Old 26 February 2014, 18:06   #12
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interesting results but surely this just proves what we all realy know that two strokes & four strokes deliver their power in different ways & at different rates

they are both 40 hp & at some point they will both produce that 40hp,they are nothing like comparing motorbikes which are rated as displacement not hp so a 125 cc 2 stroke is almost identical in hp to a 250 4 stroke although they are both totally different machines to ride

the two stroke/four stroke debate is more down to personal preference & type of use & my own opinion of what id use personally changes with the type of boat id strap the engine too

for a rib personally up to about 40/50hp id chose two stroke as smaller boats struggle more with the inevitable weight disadvantage of a 4 stroke but over that size id probably go for a 4 stroke as it would probably be on a larger boat which would carry the weight better & you would probably want to go further afield & the range becomes more of an issue

I think the 4 stroke/ 2 stroke debate will continue for some time to come as I don't think there is a definitive answer as its all about personal preferance
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Old 26 February 2014, 18:11   #13
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Cracking pic s miles and thats an "Awesome" Tuna
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Old 27 February 2014, 14:48   #14
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Great thread Miles. You might not post much but when you do, its a worthwhile read.
Treat yourself to a nice mid-00's 2-stroke and post more of the same please!!
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Old 28 February 2014, 05:35   #15
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If you are planning a re-test - other things to add to the mix:

- Diameter of gearbox / width of leg "in the water". E.g my Merc has a gearbox on a par size wise with my old Suz 25. My old Yam 55 had a gearbox I swapped with one off a 90! - the drag through the water is significant.
- Do some fiddling to get the two identically below the transom (prop shaft centrelines at same depth)

Hows about a long distance fuel consumption e.g. (assuming you have the tank capacity) an hour or known distance each way at WOT / 4500rpm / etc. I realise this will be a longer time to get meaningful results as you will need to get the tide & weather to be similar....

Also If the 2- stroke is pull start I guess it's not power trim? if so & the 4-st is getting that angle similar would also make the comparison more meaningful.

And to make a totally fair comparison can compare the purchase cost of the two - I guess you can still buy "oldschool" 2- strokes new in SA? Also then check do I need to replace the boat as well due to the extra weight of the 4 - streoke eclipsing the transom's max capacity! (not that I speak from experience or anything My transom is 110Kg max, but I have a 5m boat that clocks in at 420Kg fully fuelled....I'd love to try a back to back alongside an O-Pro with a 4- stroke 60.) But I digress.


Initial testing is fantastic and I totally for your efforts.



I did get a comparison (same hull, 2 engines) between a 1970 Yam 2 cyl and my "new" clamshell. The Yam was a long throw crank & had shedloads of Torrque. It was also manual trim. The Clamshell (arguably a similar vintage of base design) is 20 odd Kg lighter, less grunty at the low end but was (is still) a good 0.35L/NM less consumption than the Yam. (Largs in the Yam I could just make Greenock Princes Pier before it ran dry. I can now get to Helensburgh & almost back to Kip.....)
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Old 28 February 2014, 11:32   #16
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A great Post. I think very well put together for the real world boater. Very useful for someone considering changing an engine. I would not get bogged down in gear box pitch etc not prop pitch. Run the correct prop for the engine and boat combo not the same pitch on each engine.

TSM
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Old 28 February 2014, 15:48   #17
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Great post & test . and pics (I've family in Fish hoek )

I think its a very real test as the older ( much older) 2 strokes start to fail for one reason or another and are replaced by more modern 4 strokes.

I think things like eclectic start/ PTT/ noise and smooth running all play a part in decision making when weighing up a change.

The modern 2 stokes just don't seem popular in the UK ( and that from a big optimax fan) . I think the latest range of 4 stroke have overcome the weight issues of early ones ( just comparing my 2006 50 yam to a 2014 50 Honda is interesting) .
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Old 03 March 2014, 15:51   #18
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Hi

Thanx for the kind words!!

Sorry for taking so long to respond........was out fishin' with the family! (no internet!!)








Here in South Africa, we have a very different set of requirements that we would look at when choosing our outboards. On our East coast, most of the launching is done through the surf zone, which can be dead flat or on the other extreme, MONSTROUS. In these type of conditions, your hole-shot performance is what is critical.






The East coast boaters have for years complained about the 4 strokes being too sluggish and MANY boaters will buy new motors based on this premise. With the simple testing that i've done, it clearly shows that in this particular case, the 4 stroke actually has better low down performance, which is contrary to what most boaters here in SA believe (myself included!!)


Quote:
- Diameter of gearbox / width of leg "in the water". E.g my Merc has a gearbox on a par size wise with my old Suz 25. My old Yam 55 had a gearbox I swapped with one off a 90! - the drag through the water is significant.
- Do some fiddling to get the two identically below the transom (prop shaft centrelines at same depth)
9D280, both gearbox's were standard gearbox's. The bigger BIGFOOT gearbox's would make for even more interesting testing, as it swings a MUCH bigger prop, which should give better low down power. Both gearboxes looks the same to the naked eye.

Unfortunately, most boating shops fit the engines and its not always fine tuned for its application. I like my cavitation plates to be a bit higher than the bottom of my keel. This allows me to get better fuel economy, as there is less drag, as less of the motor is in the water. Both motors were mounted at the same height, as my transom is a fraction too high. This meant that they both were fitted as low down as possible, with the brackets of the motor hanging onto the transom.

Quote:
Also If the 2- stroke is pull start I guess it's not power trim? if so & the 4-st is getting that angle similar would also make the comparison more meaningful.
Both motors are non-trim and tilt. Both were set to the lowest pin. However the honda's lowest pin is a tad bit higher up than the yamaha's lowest pin, but very, very close!!

Quote:
And to make a totally fair comparison can compare the purchase cost of the two - I guess you can still buy "oldschool" 2- strokes new in SA?
I purposefully did not mention the pricing factor, as my testing was done to determine the PERFORMANCE difference between the 2 and 4 stroke motors. However, i did eventually go into the cost side of things, and even though the 4 stroke is more expensive to acquire, the 2 stroke was actually more expensive to service!! Remember, 4 strokes service intervals is 100hours, where-as 2 stroke's service interval is every 50 hours. Looking at a avid fishermans fuel savings, two stroke oil savings and service costs, it would take this boater almost 2 years to break even. Needless to say, this was based on our pricing and servicing costs. (prices i used was general list price on motors, so as to keep it fair) I then went one step further and looked at servicing the motors yourself, when your warranty runs out and the 4 stroke servicing costs for the year STILL worked out cheaper than the servicing costs of a 2 stroke for a year.


Quote:
for a rib personally up to about 40/50hp id chose two stroke as smaller boats struggle more with the inevitable weight disadvantage of a 4 stroke but over that size id probably go for a 4 stroke as it would probably be on a larger boat which would carry the weight better & you would probably want to go further afield & the range becomes more of an issue
beamishken, that was my view point too!! However, when one considers how close the difference is weight really is, the difference is maginal. In this case, the motor weighs 22kg's more than it's 2 stroke counterpart. However, you'll be using less fuel, so instead of carry 30ltrs of fuel, you can now carry 15 litres of fuel, for a trip. The fuel saving alone almost cancels out the difference in weight bewteen the two. If one was really into saving as much weight as possible, you can also start and run the 4 stroke on a motorcycle battery, which is VERY light in weight.....
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Old 03 March 2014, 20:27   #19
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Were both engines sitting at opt transom heights and running top rpm factory stated for each brand engine at wot ? Max HP is achieved near it's max rpm for a given engine to compare 40 HP to 40 HP in equal conditions as if you vere racing against each other.

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Old 04 March 2014, 10:17   #20
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Quote:
Originally Posted by Locozodiac View Post
Were both engines sitting at opt transom heights and running top rpm factory stated for each brand engine at wot ? Max HP is achieved near it's max rpm for a given engine to compare 40 HP to 40 HP in equal conditions as if you vere racing against each other.

Happy Boating
For a perfect test will need same 2 light boats, with both drivers weighting same with same amount of fuel for each one, just with a different 40 HP engine brand, both engines must be well height seated and trimmed to have boat riding paralell to water surface at wot. Doesn't matter if each one has a different prop diam or pitch or gear ratio as long both delivers full wot rpm factory stated for each model to achieve full 40 HP. Add flat calm no wind water conditions and you'll be racing equally to compare 40 HP to 40HP.

Happy Boating
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