how does this sound

[ewenm]

hi guys, i have a 17 foot glastron sx175 (2005) with 3.0l VP and sx drive

i have a 14.25 dia x 19 inch pitch 4 blade ss solas prop and my wot is 4200 with two slim adults and full fuel tank,

otherwise no weight on board, at my wot im doing 64 kmph confirmed by gps

thats about 40 mph,(39.76776 so fairly close) i cruise at 30 mph and 3500 rpm,

the specs say i should have a wot range of 4200-4400

so what do you think?? im at the lower end of acceptable, leave well enough alone or should i get the prop tweaked to reduce the pitch a little, the prop as a very slight ding in one blade, and i could get it balance and trued (prop scan)

or i could just sit back and enjoy

any thoughts or comments appreciated

EM

 

[steelespike]

Re: how does this sound

I'm not well acquainted with the VP setup but a 17 -18 ft glass boat with a 3.0 would run about 40 with a 19" - 21 inch prop.
The 19 probably would deliver a little better overall performance.
I've seen speeds claimed as much as 43 though I doubt it would do well with water sports or crowds.

 

[ewenm]

Re: how does this sound

we down graded to this boat from a 32 foot moored boat, and its purely for cruising around, no water sports, and only ever 4 adults, mostly my wife and i.

i find it fairly close to perfect, however i do take on board peoples comments of the 4 banger being noisy, and i can see that the little motor gets me to a point where i know the hull could handle more, and the efi v6 would be awesome , however for us the 4 is fine.

im just wondering if i shoud send the money to have the prop tweaked or leave well enough alone.

 

[steelespike]

Re: how does this sound

Prop pics would help.
I doubt that you could tell the difference with your prop tweaked.
It might be smoother. You might consider a new prop especially if your prop is showing its age.

 

[QC]

Re: how does this sound

What I always suggest in this situation is to buy another prop. Get the 19 as it does appear it would be more flexible for you, and then you will have the 21 as a spare. You should really carry a spare for safety anyway, so you can confirm which one is better and you have the other as a back-up. I have read, and been told by a prop manufacturer, that taking any pitch out is really not effective. Yes you will bring up the RPM, but the design will suffer. These are not words of experience though, only what others have said. The suggestion of a spare absolutely comes from experience. Many experiences :facepalm:

 

[ewenm]

Re: how does this sound

i guess what im really asking is if the fact that i can only get a wot of 4200 - 4300 is ok

everything else is fine, boat jumps out of the water, has a good top speed for what it is, and can cruise around

30mph at 3500 rpm with out sounding strained, so all considered its all good

im just asking for advice / opinions on the wot

 

[steelespike]

Re: how does this sound

4200 to 4400 seems like a narrow range. while 4200 is at the bottom of the range its not like if it was rated for 4800 max rpm.
I would assume one person with an empty tank would pop up to 4300 or so.

 

[steelespike]

Re: how does this sound

4200 to 4400 seems like a narrow range. while 4200 is at the bottom of the range its not like if it was rated for 4800 max rpm.
I would assume one person with an empty tank would pop up to 4300 or so.
I do wonder a little about the Tach assuming a 1.97 gear ratio and 10% slip 39.7 mph produces about 4800 rpm.My info indicates rpm rating is 4600.

 

[ewenm]

Re: how does this sound

after looking around I'm fairly sure I have the bull by the foot.

i will have to check, but now im thinking i have a 21 inch pitch and looking at the VP

owners manual it seems i should have a 4200 - 4600 WOT range, so if all that is true

im fairly well at the lower range, i guess i could try another prop, but as the one i have is in perfect condition and a 4 blade, a replacement one here in Australia is VERY expensive, and yes there are places that can lend out props for testing, but is it worth it for me to muck about with a set up that seems to work??

 

[QC]

Re: how does this sound

I'm getting 6% slip now, and that's too low to believe. Before you do anything else I would:

1) Verify existing pitch
2) Verify ratio (I used 1.97 as did steelespike)
3) Verify tach

No order of importance, you need to do all three Good luck mate!

P.S. Where in Australia are you? I spend quite a bit of time there and I am always interested in the boating.

 

[ewenm]

Re: how does this sound

thanks for the help , im in the only place in australia The Gold Coast

but then i,m biased

 

[ewenm]

Re: how does this sound

ok ive checked and i defiantly have a 19 inch pitch prop, so using the prop calculator and a 10% slip it would appear my tacho is wrong

running the numbers at 3500 rpm i get around 30 mph and that is what i am actually getting, however when i am doing 39 mph (GPS) the tacho is showing 4200, whereas it should be showing around 4800, as someone earlier suggested.

so looks like thats where my problem is, on the week end ill have a look and see, maybe the tach is set to 6 cyl instead of 4

ive had that happen once before, next step will be a shop tach, but at least i now have somewhere to start

thanks for the suggestions

 

[QC]

Re: how does this sound

I was at Surfer's Paradise last week of November

 

[ewenm]

Re: how does this sound

yep not a bad part of the world

 

[QC]

Re: how does this sound

Nope, agree. And I live in Southern California, another not bad part of the world

 

[ewenm]

Re: how does this sound

yep fairly similar weather i would imagine, i bet you feel it though when you come to Aus, the exchange rate is not real good, and do you find it expensive here??

 

[Scott Danforth]

Re: how does this sound

I doubt if your tach is set on 6 cylinders vs 4. my guess is the calibration is off slightly. the factory tach for all intensive purposes is just an approximation of engine RPM. get a good service tach, figure out your actual engine RPM.

 

[ewenm]

Re: how does this sound

i had a look last night and the tach is set to 4 cyl , i took a flat blade driver and cycled it a few times through all the cyl. settings.

thinking maybe there is some corrosion on the terminals??

is is possible for me to calibrate it myself?? or is that something i need to get done. is it simpler to get a new tacho, its a Fariah so fairly easy to source.

 

[Scott Danforth]

Re: how does this sound

there should be a trim pot for offset, may be under the back can.

however before you adjust anything. get your hands on a good service tach.