What speed should I be getting??

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's picture

Posts: 2029

Date Joined: 07/06/08

Boat speed

Mon, 2011-12-19 07:37

Depends on a number of factors:

  • Conditions of the ocean/weather/tides etc;
  • Weight distribution of gear in the boat;
  • Prop size; and
  • Trim which is the most important.

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's picture

Posts: 1575

Date Joined: 08/07/10

speed

Mon, 2011-12-19 07:52

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

Posts: 877

Date Joined: 03/05/11

good tips thereI thought the

Mon, 2011-12-19 07:54

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's picture

Posts: 434

Date Joined: 01/12/10

thats impressive

Mon, 2011-12-19 09:19

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!

Posts: 877

Date Joined: 03/05/11

yeh smash i was pretty

Mon, 2011-12-19 09:25

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's picture

Posts: 434

Date Joined: 01/12/10

that would be near on

Mon, 2011-12-19 09:51

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.

Posts: 877

Date Joined: 03/05/11

yes probably 45 knots. I

Mon, 2011-12-19 09:56

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

Posts: 9358

Date Joined: 21/02/08

The fact that its the

Mon, 2011-12-19 10:10

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's picture

Posts: 434

Date Joined: 01/12/10

tills right

Mon, 2011-12-19 10:23

fact is though that those figures are "astonishing" for me, for want of a better description.

Amazing performance without a doubt.

Posts: 169

Date Joined: 11/03/11

45knots with a 150 merc on a

Mon, 2011-12-19 11:32

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....

Posts: 877

Date Joined: 03/05/11

allright buddy ill take a

Mon, 2011-12-19 11:35

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

 

Posts: 210

Date Joined: 29/08/11

id agree

Mon, 2011-12-19 19:31

 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

Posts: 877

Date Joined: 03/05/11

my motor is tank

Mon, 2011-12-19 20:16

my motor is tank

Posts: 877

Date Joined: 03/05/11

the seller didn't 'tell me a

Mon, 2011-12-19 11:28

the seller didn't 'tell me a bunch of prokies' mate

Posts: 4578

Date Joined: 01/02/10

I can barely get 48 knots out

Mon, 2011-12-19 11:53

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?

Posts: 877

Date Joined: 03/05/11

35 knots= 65km/hnext time we

Mon, 2011-12-19 11:55

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?

Posts: 4578

Date Joined: 01/02/10

Make sure it's gps measured.

Mon, 2011-12-19 12:06

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?

Posts: 877

Date Joined: 03/05/11

i measure it from the

Mon, 2011-12-19 12:14

i measure it from the lowrance sounder/GPS

Grooveepants's picture

Posts: 194

Date Joined: 06/03/10

What is WOT?

Mon, 2011-12-19 20:35

?

Posts: 877

Date Joined: 03/05/11

Wide Open Throttle so as fast

Mon, 2011-12-19 20:46

Wide Open Throttle so as fast as the boat can go/ max RPM

Posts: 9358

Date Joined: 21/02/08

Wide Open Throttle.

Mon, 2011-12-19 20:54

Wide Open Throttle.

____________________________________________________________________________

CBKINETIC's picture

Posts: 62

Date Joined: 14/11/11

sounds a bit off, got a 150

Mon, 2011-12-19 12:00

sounds a bit off, got a 150 suzi on a whitley walkaround 2100 and getn about 40 knots.

 

Posts: 877

Date Joined: 03/05/11

40knots at WOT Kinetic?

Mon, 2011-12-19 12:15

40knots at WOT Kinetic?

CBKINETIC's picture

Posts: 62

Date Joined: 14/11/11

Yeah mate thats with 200 L

Mon, 2011-12-19 12:17

Yeah mate thats with 200 L fuel 3 adults and fishin gear ect.

 

Posts: 877

Date Joined: 03/05/11

ahhhhh k thanks

Mon, 2011-12-19 12:28

ahhhhh k thanks

davidbland50's picture

Posts: 392

Date Joined: 24/07/11

Not surprising

Mon, 2011-12-19 21:10

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

Posts: 877

Date Joined: 03/05/11

Yes it can be done

Mon, 2011-12-19 21:35

Yes it can be done

smash's picture

Posts: 434

Date Joined: 01/12/10

?

Tue, 2011-12-20 00:45

its only 19 foot isnt it? compared to 23 foot.

Posts: 877

Date Joined: 03/05/11

21.5 foot

Tue, 2011-12-20 07:56

21.5 foot

Bodie's picture

Posts: 3758

Date Joined: 05/11/07

gotta question that 45knot

Tue, 2011-12-20 14:52

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)

Posts: 877

Date Joined: 03/05/11

why do i have to prove

Tue, 2011-12-20 15:08

why do i have to prove myself- you either believe me or you dont?

lets get back on topic- its not even my thread....

Posts: 877

Date Joined: 03/05/11

why do i have to prove

Tue, 2011-12-20 15:08

why do i have to prove myself- you either believe me or you dont?

lets get back on topic- its not even my thread....

Posts: 877

Date Joined: 03/05/11

thats also 6.5 foot more than

Tue, 2011-12-20 15:09

thats also 6.5 foot more than mine, and weighs 600kg more?

Posts: 4578

Date Joined: 01/02/10

You forgot the double the

Tue, 2011-12-20 16:01

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's picture

Posts: 1449

Date Joined: 27/03/09

Mabye he uses BP's 98% octane

Tue, 2011-12-20 16:16

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.

Posts: 341

Date Joined: 10/08/09

motor height

Tue, 2011-12-20 16:31

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's picture

Posts: 2611

Date Joined: 03/03/09

Over 45 knots in a 6.8 Seaquest

Tue, 2011-12-20 18:47

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's picture

Posts: 2837

Date Joined: 07/07/10

my 540 traily with 90 hp gets

Tue, 2011-12-20 19:53

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's picture

Posts: 753

Date Joined: 21/02/11

It's pretty simple to tell if

Tue, 2011-12-20 20:44

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's picture

Posts: 328

Date Joined: 15/09/09

Fast Boat

Tue, 2011-12-20 20:36

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's picture

Posts: 328

Date Joined: 15/09/09

Fast Boat

Tue, 2011-12-20 20:36

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's picture

Posts: 753

Date Joined: 21/02/11

What prop are you running ?

Tue, 2011-12-20 20:41

What prop are you running ?

Posts: 4578

Date Joined: 01/02/10

And a 21in prop on a 150 on

Tue, 2011-12-20 20:36

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?

Posts: 877

Date Joined: 03/05/11

trim tabs

Wed, 2011-12-21 08:48

trim tabs

Posts: 4578

Date Joined: 01/02/10

Trim tabs don't add power.

Wed, 2011-12-21 09:11

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?

Posts: 877

Date Joined: 03/05/11

they provide elevation Also, i

Wed, 2011-12-21 09:20

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's picture

Posts: 753

Date Joined: 21/02/11

He's probably referring to my

Wed, 2011-12-21 10:19

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.

 

Posts: 877

Date Joined: 03/05/11

looking now

Wed, 2011-12-21 10:21

looking now

damo6230's picture

Posts: 2029

Date Joined: 07/06/08

Ummm that is trim

Wed, 2011-12-21 13:27

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

Posts: 877

Date Joined: 03/05/11

( I was being sarcastic)

Wed, 2011-12-21 13:31

( I was being sarcastic)

Dizzy's picture

Posts: 753

Date Joined: 21/02/11

No, but trim tabs lift a

Wed, 2011-12-21 10:14

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.

Posts: 877

Date Joined: 03/05/11

so i wouldn't really know if

Wed, 2011-12-21 10:17

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's picture

Posts: 753

Date Joined: 21/02/11

No, you tell if you're over

Wed, 2011-12-21 10:27

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.

 

 

Posts: 877

Date Joined: 03/05/11

we've reached 5500 RPM but we

Wed, 2011-12-21 10:29

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's picture

Posts: 753

Date Joined: 21/02/11

Ahh, the specs might only

Wed, 2011-12-21 10:47

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.

Posts: 877

Date Joined: 03/05/11

ha ha...we haven't changed

Wed, 2011-12-21 10:56

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's picture

Posts: 753

Date Joined: 21/02/11

Ha, no worries

Wed, 2011-12-21 10:58

Ha, no worries

Posts: 93

Date Joined: 07/10/10

To the thread starter, Would

Wed, 2011-12-21 18:16

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.