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Old 05 March 2014, 05:59   #21
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Maybe I should rephrase / calrify:

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Originally Posted by miles View Post
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.
Yeah, absuolutely, but my point was that at a high level, drag through water at the sort of speeds Ribs travel at is roughly proportional to the square of the speed & the cube of the frontal area of the object. - I.e Gearbox size is quite important!

My merc has a relatively slim gearbox (as I said, comparable to my old Suz 25Hp), but my old Yam (55Hp - so as close as in the HP dept) has a monster of a box that the production line shared with a 90Hp (so bigger to cope with the higher HP).


I'm just saying that to do a true scientific test there is a lot to take into account, and your test is the closest we've seen to date, for which .

(and realistically, what are the chances we (even as a collective) can get "smilar" engines/ hulls etc in the same place at the same time?)

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Originally Posted by miles View Post

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.

<snip>

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!!

I have an interesting parallel to that comparison. Forth cruise last year . Here's me with my 1980s vintage premix 2- stroke, one of the other boats, granted not the same hull, but the youthful helm had not got the concept of fine tuning the trim, and had parked the 1990s auto mixing 2- stroke on the bottom pin.

Both 5m ribs, both with oldschool carbed 2-stroke 60 Hp engines, so ballpark similar.

Their engine was hard down the whole trip and it looked like they were towing the Bellagio fountains behind them with the spray coming off the leg etc. I trimmed mine as high as it would go, as I usually do.

FF to halfway through the cruise. They had drained a 25L tank, I was only halfway through a 30L tank, and I had travelled Port Edgar - Granton to join the fleet before we started.


That trim angle is CRUCIAL to performance & economy - hence my asking.
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Old 05 March 2014, 08:31   #22
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Reasons a 4 stroke is better.

No oil to add
Much better on fuel
So much quieter
Happy to run at tick over all day with out fouling plug
Not witch kraft
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Old 05 March 2014, 10:38   #23
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Originally Posted by simsy View Post
Reasons a 4 stroke is better. No oil to add Much better on fuel So much quieter Happy to run at tick over all day with out fouling plug Not witch kraft
Heavier, poor punch of power/throttle response, not much better than modern 2strokes at idle, sound gay at speed , higher servicing costs.
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Old 05 March 2014, 13:01   #24
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Heavier, poor punch of power/throttle response, not much better than modern 2strokes at idle, sound gay at speed , higher servicing costs.
*apply ice to burnt area*
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Old 05 March 2014, 16:23   #25
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Fascinating read but I would like to see the test with a 40 Etec along side the 40 FS Honda.
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Old 06 March 2014, 04:42   #26
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Quote:
Originally Posted by simsy View Post
Reasons a 4 stroke is better.

No oil to add
Much better on fuel
So much quieter
Happy to run at tick over all day with out fouling plug
Not witch kraft
- nah, you just put it in a different place. (and if portable have to worry about where it goes when you take it off the boat!
- debatable at WOT / even at idle with modern DI....
- fair call, but the sound of a singing clamshell is good!
- Err auto mixers do that too!
- You need to join the magic circle!
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Old 10 March 2014, 07:12   #27
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Quote:
Originally Posted by bingbangbosh View Post
Is that not just a touch missleading

oil is used based on the fuel amount of petrol used and and in modern engine 2 strokes it burns more the higher the revs so oil must be continually added where as a 4 stroke it dose not.

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Hello & welcome!

Let's not get off on the wrong foot here. I guess at 2 posts you might not be fuilly aware of my slightly ironic side that pops up from time to time....

Stricly speaking you still need to add oil to a 4- stroke. Might only be annually, but you do need to add it...

...and the "lie it the right way up" comment is hard fact. But I guess you know that already


Quote:
Originally Posted by bingbangbosh View Post
fuel consumption: is it really debatable as I would like to see the test results that make you think so.
Indeed, which is why I am happy to see someone doijg something about it. There have been many many claims about how various engines "run on air". If you have a wee search through the forum you'll find a common theme: 1L/ mile - give or take a bit. Doesn't seem to matter if its a 25 Hp 2 stroke on the back of an SR4 or 300 Hp of 4 stroke on the back of a 7m. they all seem to drink at around the same ballpark numbers at "crusiing speed".


Quote:
Originally Posted by bingbangbosh View Post

Auto mixers also fail which is why many are turned off
Yes auto mixers fail. So do oil pumps & Engine management electrics...etc etc. Mine was probably sold with an auto mixing gizmo. I premix because I cruise and so the low RPM "leaning" of the oil would make sod all difference to my oil consumption for the amount of time I spend at idle. Premixing as you correctly say removes another possible failure. (or, if you want to be strictly accurate replaces a possible mechanical failure with human error)

Yeah, as I have said many times before If I spent all day pootling around at idle I'd not be running a premix 2- stroke. But I guess you haven't read those posts yet.

Difference is Up 'till very recently nobody had made a 4-stroke 60 that comes anywhere near 83Kg. Half the 4 strokes out there are overweight for my transom anyway.


Quote:
Originally Posted by bingbangbosh View Post
A singing clamshell! I think you need to get your ears tested. I could put up with it for a few minutes but all day! You must be joking
Nope. I like it. I bet at least some of the forum members also won't share your taste in music or cars or food or beer (whatever they may be).

Chaq'un a son gout, as our French cousins say.
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Old 10 March 2014, 09:34   #28
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No one mentioned comparing the new torqueedo Deep Blue 40hp/80hp in future test !!
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