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Post Options Post Options   Likes (0) Likes(0)   Quote clawman Quote  Post ReplyReply Direct Link To This Post Posted: 14 Jan 2019 at 5:53pm
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the prop i got was an alloy not stainless.
i find all the technical debate i have generated interesting but at the end of the day i just want the right prop.
so i had a 13.5 inch  x 15 which had too high revs- changed to a 16 inch prop as recommended which gives me a much reduced rpm at 40km per hour + sounds + feels a lot better.
will keep the technical experts posted on what i get at wot- hope its about right as i cant afford another prop.
cheers guys
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Post Options Post Options   Likes (0) Likes(0)   Quote Bounty Hunter Quote  Post ReplyReply Direct Link To This Post Posted: 14 Jan 2019 at 6:56pm
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yeah the benefits of steel over alloy in terms of flex and thinness of blades is more pronounced in larger propellers.

the additional weight of a steel prop in smaller applications often creates extra load on a small motor which isnt over come by the improved blade characteristics.

i quite like an alloy prop in smaller boats which are used for beach launching in shallow areas because any ground strike doesnt shock load the gearbox so much
 
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Post Options Post Options   Likes (0) Likes(0)   Quote clawman Quote  Post ReplyReply Direct Link To This Post Posted: 30 Jan 2019 at 8:36pm
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so got out last night to try the new prop at wot.
conditions were like a lake at makara + 2 adult free divers+ 1 child, fishing gear full tank of gas etc so a pretty normal load about average i would say for weight.
so at wot got 5400rpm + 54 kms on the gps, 57km on the speedo.
at 4200 rpm 41km on the gps + 44km on the speedo.
noticed that after doing 56km for the trip gas was half full so i reckon an improvement on fuel consumption as i would normally have maybe a third of a tank full 45 litre tank
certainly sounds + feels better from the previous prop i guess if i had a lighter load may get another 200rpm at wot.
prop is 13.5 inch x 16 previous one 13.5 inch  x 15
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Post Options Post Options   Likes (0) Likes(0)   Quote Steps Quote  Post ReplyReply Direct Link To This Post Posted: 31 Jan 2019 at 10:11am
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5400rpm + 54 kms (33mph)
4200 rpm 41km (26 mph)
13.5 inch x 16
yammy 100hp  4 stroke  2.31:1 gear ratio  Correct?
Max rpm range 5000 to 6000 rpms  Correct?
5.45m aqualine This is an open boat.. no cabin?

That brings the gross weight on the water around 1750kg
 Boat of that size design should be coming in around 1000/1150kg

 Strongly suspect the engine height incorrect.. too low 
 A boat of that weight would have a WoT around 42/42 mph

 WoT Rpms where should be for a general use boat.. mid way or marginally below midway..5400 very good

 WoT slip 6.8%  good
4200 cruise slip 5.6% wrong should be for that boat weight/size around 12% to 15%
 To have 6.8% @5400 WoT and a lower slip at cruise is impossible... cruise would be approx 23/24 mph (38/39km
 This is suspect data

Based on new data, and data of other boats similar weight. power size...
With 100/110 hp at the prop if engine right height, no permatrim, no cabin, gross weight on water around 1100kg
Should have A WoT @ approx 5% slip 5400 rpms 42/43 mph.(67/68km)
 A 4000 rpm cruise @approx 13% slip  28/29 mph (45/46km)
 Have  a 19" pitch prop and approx 13 3/4 to 14" 1/4 diameter.

noticed that after doing 56km for the trip gas was half full so i reckon an improvement on fuel consumption as i would normally have maybe a third of a tank full 45 litre tank

Assuming the tank is rectangular in shape, no sides/ ends tapered etc..and that the tank float position moves when the fuel is 1st started to be used.. moves off the F mark very soon..

 EDIT:
 If so then 56km on approx 22L....that pretty good.. thu you are cruising at 26 mph.. I would more expect, at least 1l per nautical mile.. thats near 1l per 2km

 Only way to check usage is fill up at THE pump, then fill up again at the THE pump facing the same way..most of courts have a slope.., most boats the fill is at the rear of the tank.. so idea direction is to have the boat facing down hill.. yep 1 or 2deg makes a lot difference to data with a long tank and air lock the front section.

 And at that speed should be a damn sight better... cruising faster at lower rpms with leaner mixture
 Check engine height is correct
 And get several lots of data
 From around 3500 thru to WoT .. IF a particular reading is incorrect it shows up as a an anomaly
 The cruise numbers are suspect..
 The WoT number if correct indicate low engine, extra drag.. in effect throwing extra weight into the boat..
 








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Post Options Post Options   Likes (0) Likes(0)   Quote clawman Quote  Post ReplyReply Direct Link To This Post Posted: 31 Jan 2019 at 5:49pm
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hi steps
the boat does have a bimini  top so i guess a bit extra drag.
motor is at the top notch so cant go any higher + the readings were corrrect.
next time i am out i will take some more details through out the rev range.
cant keep changing props so im feeling like the 13.5 inch x 16 is the best in practice- cant comment on the theoretical stuff
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Post Options Post Options   Likes (0) Likes(0)   Quote Steps Quote  Post ReplyReply Direct Link To This Post Posted: 31 Jan 2019 at 7:16pm
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Bimini wil not cause that sort of drag at cruise

 To have 6.8% @5400 WoT and a lower slip at cruise is impossible... cruise would be approx 23/24 mph (38/39km
 This is suspect data

Engine height.. wave a phone around the stern at cruise best rim get some pics of the cavitation plate...

cant keep changing props
 Just watch trademe.. even an alloy 14 " 19 pitch .. pick them up for $50..
Since it is a 'cruise' boat, mid range weight, the amount of flex between an alloy and SS will be so small would never notice the diff...the economy significant.
 Will drop the 5400 a little more.
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Post Options Post Options   Likes (0) Likes(0)   Quote clawman Quote  Post ReplyReply Direct Link To This Post Posted: 01 Feb 2019 at 7:55pm
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hi steps
dug out the owners manual + i have a f100 det + the gear ratio would seem to be 2.27(25/11)  not sure what all that means seems to be the same gear ratio for  75,80,90,+100hp motors
does this make any difference in your calcs?
also called in to another yamahs dealer here in wgton + ran through the differences with the 2 props.
his opinion was that the current prop  is all good + given that i had a reasonable load on board when i tried wot then 5400rpm for 54km per hour was spot on.
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Post Options Post Options   Likes (0) Likes(0)   Quote Steps Quote  Post ReplyReply Direct Link To This Post Posted: 02 Feb 2019 at 9:26am
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Data correction gives 
 8.5% slip @ 5400 33mph from 6.8%  indicates a a a slightly larger prop required for a little more grip

7.3% slip @ 4200 26 mph from 5.6%

Which is impossible to have the cruise.. boat lower in the water ,  far more  surface area, more friction, with less slip.

 Assuming the data error in at cruise  then slip would be around 18 to 20% which would give  a speed approx 22/23 mph  or if rpms wrong...4870 rpms.

If the cruise was right that would put WoT into the - numbers which means the boat is going faster than the prop is turning..
 Without good accurate data it is impossible to make good accurate assessments of the props...
 Be it off the cuff, hit in miss or crunching numbers.

 Hence why it is important to get readings by on flat water
 1/ set rpms around 3500 rpms.. then trim up to best trim..just before ventilation and/ or just as starts to propose
 Take the rpms (these will increase) and speed
 2/ repeat again at  approx 4000, 4500, 5000 thru to WoT

Any anomalies, bad data will then show up, and general there is 1 or 2 data readings that will be crook.

 How someone can assess 2 props without accurate slip data or knowing the slips is at best a wild guesstimate..
 Not my opinion , but substantiated by all major marine architects for the last 100 yrs or so.
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Post Options Post Options   Likes (0) Likes(0)   Quote davv Quote  Post ReplyReply Direct Link To This Post Posted: 27 Feb 2019 at 10:09am
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Has anyone out there got a yami 150 Vmax HPDI  05 ?    I've heard good things about them in regards to fuel economy and read articles that suggest fuel burn is very similar to the yami F150  @ 4-5000 rpm but not so good at the lower rpm   Tried looking for figures on old threads but no luck. Only asking as I'm looking at one on a 6m style pontoon hull but I do a lot of work at idle slowing the drift in deep water so just doing a little homework. Any experiences or advice would be appreciated .
Cheers
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Post Options Post Options   Likes (0) Likes(0)   Quote Steps Quote  Post ReplyReply Direct Link To This Post Posted: 27 Feb 2019 at 10:44am
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Fuel economy is dependant to
1/ powered for the end use/ weight of boat
1/ correct propping for the application.. all the following will have different props
ie trolling displacement hull.. here longer the hull the better
General use.
 Sking towing
racing.

 Difficulty comes in when lower in the required power for a end use and then also going to use for something else.
 eg a/ Getting to trolling grounds, the trolling all day
 b/ general use boat , then towing skiers.

A well powered boat within reason suits ac 'compromise ' prop...

Also well powered means leaner burn , less  power head loading, (throttle) and less rpms.

 If repowering , ideally need to take data off the old engine, gross boat weight..
 Identify the parameters.. speeds  etc wish to travel at... then make a choice of power option at the prop
 From their one then chooses make , model etc.

 At the end of the day thu.. if well set up the differences if any are very little in real life practical terms... WHEN the same (not identical) boat loaded the same way (same ppl same fel load etc) between 2 different engines.
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Post Options Post Options   Likes (0) Likes(0)   Quote davv Quote  Post ReplyReply Direct Link To This Post Posted: 27 Feb 2019 at 11:22am
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Thanks Steps -yep a very logical thought process that makes sense in the 2st vs 4st debates Having said that its always good to hear from people that have actually owned something your looking at and listen to their experiences. Ack that they are personal exprriences though and one size doesn't always fit all lol. Any owners ex owners out there anywhere?
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Post Options Post Options   Likes (0) Likes(0)   Quote Bounty Hunter Quote  Post ReplyReply Direct Link To This Post Posted: 27 Feb 2019 at 12:10pm
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had a 200hpdi - one of the later editions with the higher rail pressure and black graphics. 
150 and 200 were essentially the same motor.

i would consider it one of yamahas best ever engines. certainly very quiet - moreso than their 4strokes of same era.

stay away from the 250 and 300hpdi which were well known for blowing up.

fuel eco was excellent - but we had it on a smaller hull than yours - and were getting 1l/nm from 25-40mph

behaviour and fuel use at idle was excellent - remember that the injection 2strokes are inherently better on fuel at idle because theyre not having to run a valvetrain.
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Post Options Post Options   Likes (0) Likes(0)   Quote Tagit Quote  Post ReplyReply Direct Link To This Post Posted: 27 Feb 2019 at 1:17pm
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Had a 200HPDI which as above is the same engine at a higher tune. Good engines and one of the best ever 2 strokes. 
BH nailed it above I think other than saying that they are not normally as economical as the 4 strokes when trolling. If just idling around and cruising I don't think you would see much difference at the end of a day. What difference there would be would be more than compensated by the difference in purchase costs. Note that the latest gen 4 strokes with 'lean burn' etc are a bit more economical. Comments about being similar to the F150 etc are talking abut first gen 4 strokes not the latest stuff.
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Post Options Post Options   Likes (0) Likes(0)   Quote davv Quote  Post ReplyReply Direct Link To This Post Posted: 27 Feb 2019 at 2:46pm
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Thanks heaps for sharing everyone, I appreciate your time,experiences and thoughts particularly as I contemplate making the move from a bulletproof yammi F100 4 s after 10yrs to a 2s-something that I'd never really envisaged ever being likely

sounds like if I do make the move, I'm comforted by the fact they were one of the best for their relevant era
Cheers
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Post Options Post Options   Likes (0) Likes(0)   Quote Betty Boop Quote  Post ReplyReply Direct Link To This Post Posted: 27 Mar 2019 at 2:05pm
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I did a more precise evaluation yesturday in Betty Boop, 6x metre fi-Glass viscount, Bracketed '02 150hp carb'd 2stroke Johnson, with 300litres of fuel in her belly. Total of 14.9 miles travelled, at 3250rpm 27mph, with a 2minute squirt at 5150rpm, WOT, 42mph(GPS) returned a total fuel burn of 18xlitres....1.29litres per statute mile.Geek
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Post Options Post Options   Likes (1) Likes(1)   Quote Steps Quote  Post ReplyReply Direct Link To This Post Posted: 28 Mar 2019 at 2:03pm
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I recon that's about as good as it gets.. A boat that weight that hp and 2 mins most proberly 2x plus the consumption at cruise..
You have about a 1 7"pitch prop? Big diameter 14 3/4 plus diam?

The 5150 42mph WoT.. or close to it?
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Post Options Post Options   Likes (0) Likes(0)   Quote Polar_Kiwis Quote  Post ReplyReply Direct Link To This Post Posted: 28 Mar 2019 at 6:22pm
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I have an Atomix 500 rib and 2004 Merc 60hp efi four stroke.
Just hooked up simrad and mercury vessel link computer.

Getting about 1.8nm/litre.

Usually loaded up for day adventures softbaiting.
Here fishy, fishy fishy.... Nom, nom, nom
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Post Options Post Options   Likes (0) Likes(0)   Quote Bill fisher 5.5 Quote  Post ReplyReply Direct Link To This Post Posted: 07 Apr 2020 at 6:42pm
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Brand new to this site guys.
I have a Buccaneer Billfisher 5.5 with a 2014 Yamaha 115. I do all sorts of fishing on it. I feel like it’s a bit under powered and uses more fuel because it’s always working a bit harder.
ie trolling at 7 knots it’s using 10lph.
Hoping I can talk with other people with similar sized boats, what motor you have and how it goes or one of you experts can help me out on being more economical and talk about a better sized motor.
Cheers guys
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Post Options Post Options   Likes (0) Likes(0)   Quote Steps Quote  Post ReplyReply Direct Link To This Post Posted: 07 Apr 2020 at 8:04pm
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maybe min powered ???
 1st thing is the engine the corect height, then go from there.
Out boards do not have a gear box , therefore the props are selected for end use... unless in some cases when rather over powered.
Eg a boat used for sking will have maybe a slightly larger prop but lower pitch.. the same boat cruising will have more pitch.
A boat used for trolling will have a large  diameter and pitch to suit the rpms.
So ideally u have one pitch to get out and another to troll with.
 Now to throw something else in..
trolling is not planing , rather than weight the being what tp power to  at plane, You are displacement hull on the troll.. here length at the water line determines everything.
 IE a longer hull will be far more economic than a shorter hull.
 Hence why you will find bigger boats 6/ 6 /8m go out and can troll on a oily rag.
Before doing anything , even thinking under powered , the engine must be the correct height at cruise  with trim just before proposing  or cavatation.
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Post Options Post Options   Likes (0) Likes(0)   Quote Bounty Hunter Quote  Post ReplyReply Direct Link To This Post Posted: 07 Apr 2020 at 8:40pm
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Originally posted by Bill fisher 5.5 Bill fisher 5.5 wrote:

Brand new to this site guys.
I have a Buccaneer Billfisher 5.5 with a 2014 Yamaha 115. I do all sorts of fishing on it. I feel like it’s a bit under powered and uses more fuel because it’s always working a bit harder.
ie trolling at 7 knots it’s using 10lph.
Hoping I can talk with other people with similar sized boats, what motor you have and how it goes or one of you experts can help me out on being more economical and talk about a better sized motor.
Cheers guys

had the 565 with a 200hpdi - that was good - 1litre per NM up to almost 40kts

i think youre expecting too much for the hull length - 7kts is something like 1.8:1 speed:length ratio - anything over about 1.3-1.4:1 is real inefficient

have a think about the type of lures youre dragging - set a spread that works better at 6kts and enjoy the savings.


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