What speed should I be getting??
Submitted by Grooveepants on Mon, 2011-12-19 06:00
I have a 5.6 quinnie classic runabout with a 90hp honda on the back and was wondering what speed I should be getting from it?
I just saw this thread http://fishwrecked.com/forum/trailcraft-540-profish-sale and he's getting 30-35knts from his 90hp at 5000rpm but I'm sure I don't come close to this.
Is there something you can do to get more speed?
Also how many rpms should you run your motor at to use less fuel and give the motor more life?
damo6230
Posts: 2029
Date Joined: 07/06/08
Boat speed
Depends on a number of factors:
All these factors take time to learn but once you find your boats sweet spot its easy cruising.
Trim to me is the most important factor and you should always have your finger on the trim button. Your boat will have all the weight up at the stern whereas the profish at the transom so there is a big different in weight distribution and thus ride. Experiment with your load and find your sweet spot.
Presently I'm running a standrard prop which gives me top end speed but if I want to do long distance cruising then I should swap to a bigger one (at the loss of speed but better cruising / fuel efficency under load).
I would think you could get similar speed out of your engine given your hull.
Most motors run the best / most economical at 4200-4800rpm. These days one can expect 4000-5000 hours out of a motor
Dont forget that a knot is 1.85km. I get the same speed as above (and if we use the spring tides I can easily add another 15km/hr to my speed for the same rpm) and dont forget that the above speed is probably in calm water.
Ryan C
Posts: 1575
Date Joined: 08/07/10
speed
hi mate i used to have a 560 quinnie spirit(half cab) with a 90 honda and i used to get 33 knots top end on flat water. cheers
Swan River Fisher
Posts: 877
Date Joined: 03/05/11
good tips thereI thought the
good tips there
I thought the motors optimum range was 3000-3500 RPM?
I have a 6.7m trophy with a 150 merc which still goes 35km at 3500 RPM in moderate conditions and 72km at 5000 RPM calm conditions
Your honda should last for a few thousand hours as Damo said
With a 90 on the back i would guess you'd reach probably 30 knots with 2 people and fishing gear.
Do you fish or dive? Diving gear adds a lot of weight to your vessel.
A mate had to upgrade motors on his 5.6m from 115 to 150 due to the weight.
smash
Posts: 434
Date Joined: 01/12/10
thats impressive
72kmh from a 150 merc on a 6.7 deepV glass boat that Im guessing weighs over 2 tonnes? and at 5000 RPM? What does it do at WOT? cos it may even be overpropped if thats full bore, depending on the engine and still getting just about 40 knots!
Swan River Fisher
Posts: 877
Date Joined: 03/05/11
yeh smash i was pretty
yeh smash i was pretty surprised because i thought a 150 was too light on. Yep about 2.1 tonnes with 225L petrol and fishing gear. Yes at 5000RPM.
Never tested it at WOT because the times we have been out have been a bit crap. I dont think 5000 RPM is max i think somewhere around 5750 RPM. But we don't often travel at WOT because over time its not too good for the motor.
Probably going to upgrade it in a few years to a 200 Yammy 4 stroke- then we can see how fast it goes haha
ill check the prop and see what size it is.
smash
Posts: 434
Date Joined: 01/12/10
that would be near on
that would be near on 45-50knots at 5750?
And your right, its not good to run it at the speeds regularly-BUT its even worse to be OVERPROPPED, much worse in fact even if not running it at WOT.
Much like driving your car at 40kmh in overdrive towing and flat to the floor.
Swan River Fisher
Posts: 877
Date Joined: 03/05/11
yes probably 45 knots. I
yes probably 45 knots. I don't think its overpropped because its the original prop that came with the new boat in 2001
Where does it say the size? i had a check but couldn't see
till
Posts: 9358
Date Joined: 21/02/08
The fact that its the
The fact that its the original prop means nothing. The mnanufactuer had no idea where you were going to use, how you were going to use, if you were going to use it loaded etc etc.
Besides, you have no idea if it was really the original prop as you didn't get it new, and lets face it, the seller told you guys a bunch of porkies.
The prop has a serial number on it, and that should give you the size and pitch. Failing that you can get out a tape.
smash
Posts: 434
Date Joined: 01/12/10
tills right
fact is though that those figures are "astonishing" for me, for want of a better description.
Amazing performance without a doubt.
FISHNTIME
Posts: 169
Date Joined: 11/03/11
45knots with a 150 merc on a
45knots with a 150 merc on a trophy lol i really doubt it. I had a suzuki 300hp on a 23ft fraser and would only get 43knots at WOT
But with the 90hp on that set up i would say 25/30knots depending on weight....
Swan River Fisher
Posts: 877
Date Joined: 03/05/11
allright buddy ill take a
allright buddy ill take a picture next time were out
And i have only been 72km/h at 5000RPM 45 knots was just an estimate
greatrex
Posts: 210
Date Joined: 29/08/11
id agree
the missus old man just bought a 21ft trophy centre console with a 150hp verado and it doesnt get anywhere near that maxs out about 32knots full throttle...that would be alot lighter then his
Swan River Fisher
Posts: 877
Date Joined: 03/05/11
my motor is tank
my motor is tank
Swan River Fisher
Posts: 877
Date Joined: 03/05/11
the seller didn't 'tell me a
the seller didn't 'tell me a bunch of prokies' mate
dodgy
Posts: 4578
Date Joined: 01/02/10
I can barely get 48 knots out
I can barely get 48 knots out of my 17r Haines with the 150. Much lighter than a trophy. Be suprised if you measured more than 35 knots wot.
Does anyone know where the love of god goes, when the waves turn the minutes to hours?
Swan River Fisher
Posts: 877
Date Joined: 03/05/11
35 knots= 65km/hnext time we
35 knots= 65km/h
next time we go ill make sure i get a picture of it.
Groovey what speed do you currently get at WOT?
dodgy
Posts: 4578
Date Joined: 01/02/10
Make sure it's gps measured.
Make sure it's gps measured. Much more accurate than a pitot tube style speedo.
Does anyone know where the love of god goes, when the waves turn the minutes to hours?
Swan River Fisher
Posts: 877
Date Joined: 03/05/11
i measure it from the
i measure it from the lowrance sounder/GPS
Grooveepants
Posts: 194
Date Joined: 06/03/10
What is WOT?
?
Swan River Fisher
Posts: 877
Date Joined: 03/05/11
Wide Open Throttle so as fast
Wide Open Throttle so as fast as the boat can go/ max RPM
till
Posts: 9358
Date Joined: 21/02/08
Wide Open Throttle.
Wide Open Throttle.
CBKINETIC
Posts: 62
Date Joined: 14/11/11
sounds a bit off, got a 150
sounds a bit off, got a 150 suzi on a whitley walkaround 2100 and getn about 40 knots.
Swan River Fisher
Posts: 877
Date Joined: 03/05/11
40knots at WOT Kinetic?
40knots at WOT Kinetic?
CBKINETIC
Posts: 62
Date Joined: 14/11/11
Yeah mate thats with 200 L
Yeah mate thats with 200 L fuel 3 adults and fishin gear ect.
Swan River Fisher
Posts: 877
Date Joined: 03/05/11
ahhhhh k thanks
ahhhhh k thanks
davidbland50
Posts: 392
Date Joined: 24/07/11
Not surprising
My new Douglass Craft has a 93 Johnson running a 17 prop and we have had it doing 42knots at WOT. So really, it can be done.
Wherever you go, there you are
Swan River Fisher
Posts: 877
Date Joined: 03/05/11
Yes it can be done
Yes it can be done
smash
Posts: 434
Date Joined: 01/12/10
?
its only 19 foot isnt it? compared to 23 foot.
Swan River Fisher
Posts: 877
Date Joined: 03/05/11
21.5 foot
21.5 foot
Bodie
Posts: 3758
Date Joined: 05/11/07
gotta question that 45knot
gotta question that 45knot guess too swan river.
Mines got twin 140's and weigh's about 2.5 tonne, i can only get 40 knots on the river. Ocean wise usually 37ish.
I know the the last 28 Fury build had twin 225 Yammy's, it did 47 knots. Weight is about 2.7ish T
Thats 450hp, 3 times what your running (albiet a different hull and weight)
Swan River Fisher
Posts: 877
Date Joined: 03/05/11
why do i have to prove
why do i have to prove myself- you either believe me or you dont?
lets get back on topic- its not even my thread....
Swan River Fisher
Posts: 877
Date Joined: 03/05/11
why do i have to prove
why do i have to prove myself- you either believe me or you dont?
lets get back on topic- its not even my thread....
Swan River Fisher
Posts: 877
Date Joined: 03/05/11
thats also 6.5 foot more than
thats also 6.5 foot more than mine, and weighs 600kg more?
dodgy
Posts: 4578
Date Joined: 01/02/10
You forgot the double the
You forgot the double the power bit....
Does anyone know where the love of god goes, when the waves turn the minutes to hours?
Paul_86
Posts: 1449
Date Joined: 27/03/09
Mabye he uses BP's 98% octane
Mabye he uses BP's 98% octane fuel, used to work with a guy who reakons his commodore got an extra 50 rwhp from using it ;) lol.
stilly
Posts: 341
Date Joined: 10/08/09
motor height
is the motor set up correctly on transom? props will get you different hole-shot and on the plane speeds and will also alter topend considerably, but you lose one to gain the other generally, at a guess i would be happy with "near perfect" weather to get 27-32kn flat strap with your set-up, as for rpm range vary it and you cant go wrong, but i will say keep that disprin.....i mean honda moving or you may just lose that gearbox !
sunshine
Posts: 2611
Date Joined: 03/03/09
Over 45 knots in a 6.8 Seaquest
200 Jonno At WOT ...............sat on 36 knots on Saturday all the way across the Sound early whilst it was really flat, only slowed due to swell effects as we enterred the channel between GI and Carnac where it really shallows off.
Only ever ran it flat out out at the Northern Group on an utterly flat glass off day with no swell - really frightening at that speed as the steering was featherlight. Stupid really and would never try it again
We run a 4 blade stainless
JohnF
Posts: 2837
Date Joined: 07/07/10
my 540 traily with 90 hp gets
my 540 traily with 90 hp gets 29 knots flat knacker on a good day, 28 normally.
I raised the prop one notch and got 30 flat tack, but it cavitated on turns and breeched easily, so dropped it and all good now, but 28 is it.
Make sure it is GPS, the normal speedos are a load of rubbish.
In an ali hull, hardly ever need over 30 knots anyhow.....unless you want to get a few inches shorter.
Boston Whaler 235 Conquest......getting the flogging it was built for.
Dizzy
Posts: 753
Date Joined: 21/02/11
It's pretty simple to tell if
It's pretty simple to tell if someone's bullshitting about boat speed.
You take the Engine Revs, Gearbox ratio and prop pitch and you work out the absolute maximum that combo can achieve.
I've met wankers that claim 50knots @ 5500rpm with a 200hp Optimax on a big pacemaker I was looking at.
Then I walked around and saw they only had a 19" prop - so I told them either their GPS was stuffed, or they were FOS.
It just ain't mathematically possible.
I'd been looking at a boat with an optimax, so knew the 200hp had a 1.75:1 gear ratio, and had already been doing prop calcs for the boat I was looking at.
To do it long-hand (for those who are interested) :
For their rig that meant @ 5500rpm through a 1.75 ratio gearbox, the prop was spinning 3142.8 times every minute
3142.8 x 19" = 59713.2 inches / minute
59713.2 inches/min = 1516.715 metres/min
1516.715 metres/min = 91km/h
91km/h = 49.1 knots
So 49.1knots was the absolute maximum speed that boat could travel - and that's with zero prop slip due to drag / friction / shit prop.
Take off another 10-15%+ for prop slip, and a more realistic figure was 42'ish knots - which is still impressive - but didn't make them any less FOS.
Based on those figures, and Swannie's 1.87 ratio in his 150hp Saltwater you'd have to have a 21" pitch prop on it and getting around 15% slip to get 72kmh @5000rpm
(Either that, or you're running a 19" and getting 7% slip, which ain't going to happen)
With a boat that size I reckon you'll battle to squeeze another 500rpm out of the 150 - so you may be overpropped.
Even if you do (and your figures are right), another 500rpm will take you to around 79km/h (42.6 knots)
Other than that, you've got a 19" prop and are FOS too !
Fuck, how'd I manage to dribble that much shit in so little time ??
Kingfisher549
Posts: 328
Date Joined: 15/09/09
Fast Boat
I have a Baron Sportsman 5.85mtre with a 225hp merc, had to 54knots, scary sh..t, still had more throttle to go. the only thing im interested in is motor not working hard and fuel economy, my motor gives me both. Oh and when its flat scare the crap out of jetskiers.
Baron Sportsman Custom
Kingfisher549
Posts: 328
Date Joined: 15/09/09
Fast Boat
I have a Baron Sportsman 5.85mtre with a 225hp merc, had to 54knots, scary sh..t, still had more throttle to go. the only thing im interested in is motor not working hard and fuel economy, my motor gives me both. Oh and when its flat scare the crap out of jetskiers.
Baron Sportsman Custom
Dizzy
Posts: 753
Date Joined: 21/02/11
What prop are you running ?
What prop are you running ?
dodgy
Posts: 4578
Date Joined: 01/02/10
And a 21in prop on a 150 on
And a 21in prop on a 150 on that boat is going to take 10 mins to get onto the plane....
Does anyone know where the love of god goes, when the waves turn the minutes to hours?
Swan River Fisher
Posts: 877
Date Joined: 03/05/11
trim tabs
trim tabs
dodgy
Posts: 4578
Date Joined: 01/02/10
Trim tabs don't add power.
Trim tabs don't add power. Running a 21 in prop without the power to spin it to wot is the same as trying to take off fro
the traffic lights in 4th....
Never argue with an idiot. They just drag you down to their level and beat you with experience...
Does anyone know where the love of god goes, when the waves turn the minutes to hours?
Swan River Fisher
Posts: 877
Date Joined: 03/05/11
they provide elevation Also, i
they provide elevation
Also, i dont know about you guys but i can change the angle of the motor to help get the bow up?
And who said i had a 21 inch prop on it?
Dizzy
Posts: 753
Date Joined: 21/02/11
He's probably referring to my
He's probably referring to my long-winded post on props Ben - where I made a calc from your revs / speed to take a guess at your prop pitch.
Go and have a look when you get the chance - should be in the casting somewhere - look for something that says 3x15x19 or something like that.
BxDxP
B = number of blades
D = Prop Diameter
P = Prop Pitch.
Swan River Fisher
Posts: 877
Date Joined: 03/05/11
looking now
looking now
damo6230
Posts: 2029
Date Joined: 07/06/08
Ummm that is trim
kind of said it's pretty important straight up above.
pretty much any motor can be trimmed up or down but like any technology it's only as good as the monkey controlling it
Swan River Fisher
Posts: 877
Date Joined: 03/05/11
( I was being sarcastic)
( I was being sarcastic)
Dizzy
Posts: 753
Date Joined: 21/02/11
No, but trim tabs lift a
No, but trim tabs lift a heavy ass out of the water and get it onto the plane much quicker, which is what SRF was inferring.
Swan River Fisher
Posts: 877
Date Joined: 03/05/11
so i wouldn't really know if
so i wouldn't really know if it was overpropped because we cant tell how long it takes to get on the plane due to the effect of the trim tabs.
Dizzy
Posts: 753
Date Joined: 21/02/11
No, you tell if you're over
No, you tell if you're over propped if you can't reach the maximum recommended revs for your engine.
If she gets up and planes easy with the trim tabs, it's all good, but you can't gauge your suitable prop from that.
You've mentioned you've hit 5000, which is right on the lower limit of the 5000-5600 recommended range.
You need to open her up, trim it well and see what she hits WOT - with your usual expected load, so you're propping it for the kind of conditions you're intending to use it in.
Swan River Fisher
Posts: 877
Date Joined: 03/05/11
we've reached 5500 RPM but we
we've reached 5500 RPM but we had alot of people on so it was no where near as quick as when we measured it at 5000 RPM
Also, im no retard, but the prop blades and inside it near the impellor and all around it is blank- no writing what so ever
Dizzy
Posts: 753
Date Joined: 21/02/11
Ahh, the specs might only
Ahh, the specs might only visible with the prop off.
Well that just confuses things - because if you hit 5500 with a full load then that's a good prop match for the boat. (unless it's a ridiculously small diameter and your getting major slip).
But it also means that you surely must be running a smaller pitch prop for a 150hp to be spinning 5500 on that heavy boat with a full load.
And if that's the case, the 72kmh speed @ 5000 doesn't quite calc. (unless you had a major tailwind or something)
Doesn't matter what speed you're getting - if you're getting 5500rpm it's all good, just go and check the speed again - maybe the GPS was giving a few dodgy readings hehe.
Swan River Fisher
Posts: 877
Date Joined: 03/05/11
ha ha...we haven't changed
ha ha...
we haven't changed the prop on the trophy
ill check the readings again but i am 110% sure we got 72km at 5000 RPM
ill take a picture for you
Dizzy
Posts: 753
Date Joined: 21/02/11
Ha, no worries
Ha, no worries
hamo
Posts: 93
Date Joined: 07/10/10
To the thread starter, Would
To the thread starter, Would expect around 28-30 knts with a couple of blokes on board.
I've got no less than 4 props for the 175 Merc on my Trophy. 3 and 4 blade, 14-19 inch . No way known I can get any better than 31-32 knots out of it flat strap on a day as flat as a tack. 1/2 a tank of juice and no real gear to speak of. With the 4 bladed 17x14 1/4 it'll do 30 knots but it's so over propped it'll only turn to 4600-4700 RPM.
If i remember rightly the stock prop off my 175 is a 17x19 alloy thing, size and pitch are embossed on the insidide exhaust vent area and may be covered by the retaining nut and washer.