Geez the bickering 'round here between a certain 2 is ummmmmmmmmmmm

















BLOODY GREAT i love it!!!!


BTW thanx for BOTH answers

SMELLY

'there's always 3 sides to a story.My side,your side and the TRUTH '

Just been wondring, do you think if there was humidity or was raining that the prop would spin faster? would it have more power or would it cause water to get in the fuel tank? Mayb the power came from th fuel station?

Changing props is usually to get a differant pitch or prop style, and they are generally stainless cause its what sells and what people want when paying big dollars for a prop, especially with racing/skiing boats and they want it to last longer.

You want a race prop you want the shiny one, I like shiny things, like spoons!

Also agree that correct trim of the motor and correct HP will give the correct ride without need for any additions.

Fed what makes you think the composition of metals in props has changed in the past 30 years ???

Here's a good example aeroplanes used to use wooden props back in the old days & still used to fly didn't they ??

Material composition of props has no bearing on it's performance what governs that is the way it's cupped or the pitch

Rum you ninkompoopy red paint is no good all that will do is attract BULL sh*t you need to paint GT stripes to go faster

Everyone (except Jumpy) should visit the Mercury Propeller site there's some very good info available there.
http://sites.mercurymarine.com/portal/page...;_schema=PORTAL


But they fly better now because newer materials allow them to use more efficient designs.


Nowdays there's not a great deal of difference between SS & Alloy as the alloy materials they are using are getting better all the time.
Interestingly Mercury are claiming that X7 alloy is even better than SS so any differences would have to be considered marginal at best.

I think for a normal fishing boat it now makes very little difference and for any ventilation problems other solutions like lowering the motor would achieve a better result.

bugger this i am buying the 4stroke i will polish the prop till it shines like silver then paint it red and see how it go's that way i should be able to raise the motor two holes
now that i have had some fun, it is the quietness of the 4stroke that appeals to me + the fact that i intend to do a lot of trolling over the summer months.
Yamaha 2 strokes run at 50 to one oil injection which will oil up the plugs at low revs, that is not acceptable to me, so that is the main reason for the 4 stroke second to that is the resale will be enhanced believe it or not.
a Jarvis water snake will be fitted at some point when i start the build i shall post pitchers of just how ease it is to work on a poly.

Fed in your last remark you've come right around back to what I initially pointed out.

No good even bothering to visit links like the one you posted simply because they would be refering to performance race motors irrellevant to how a fisherman would drive his boat.

Those guys are full on & may carry up to 1/2 doz different props & not choose one till just b4 the run

Do you have a GPS Poly, any chance of getting some speed readings before you change the motor to compare against the new one?

RDnR, you may want to reconsider your ideas on power & torque, here's a handy little program for you to play with.
http://www.comcen.com.au/~fed/convert.zip
I keep it in my quicklaunch bar right beside my spellchecker.

no GPS Fed i think it dose about 28 or 30 k's maybe

Fed they are not My Ideas, they are facts on how horsepower and tourqe are related.

Even in your nice little program you cannot compare torque to horsepower.....

Boy poly you have alot of Katsika's in your goat

How many Billy's chase them ??

??????????????????????????????????????????????

This is the part that's got me scratching my head RDnR.

That is Exactly how horsepower is figured out...

Horsepower = The engine torque x RPM , Divided by 5252

i forget the tecnical name for the it but at 5252hp torque and horsepower are always equel
as the HP and the Tourqe rise they meet at this point.

On the engine the horsepower is always going to be stated as a MAX Hp.

My argument is that 2 stroke engines hold there MAX or close to there Max HP for a much longer time through the Rev Range. Due to the Cycles of the engine. The 2 stroke engine delivers power more often that the 4 stroke engine, thus giving it greater torque, and there fore a better range through the power curve.

Katsika's are Nanny goats poly

We were sitting hear trying to figure out what the k's in



Stood for & assumed they were Katsika's

I would think she would go faster than that poly.

Our boat with 30hp on it does 40kmph. 30km's is only around 20 knots.

You must be right RDnR, I read it on the internet.
http://www.v8914.com/Horsepower-v-torque.htm
I can't believe I got this old without knowing that stuff.
I think I'll have to read it a few more times to get my head around it.

Yea thats a good article! Ive only skimmed through it though...

you are most likely to be right chad how much dose your boat weigh, the poly is 264kg's +my 73kg's +possum and no i will not reveal her weight + about 25kg's of gear not to mention fuel 50lts 10lts of water, one of these days i will get around to weighting her, i think i need a bigger motor

I am giving an update on the new motor for any one how has not been following this thread i replaced the 30hp 2stroke on my poly with a 40hp 4stroke and the diferance is amazing.
there were two main reasons for the change (1) hole shot as the 30 was struggling to get her up (2) noise was excessive being a tiller steer it made it impossible to hear people talking to me, top end speed was not a real factor in my thinking as i am one of those people how like to sit back and enjoy the ride.
the motor now has 8hrs on it so i gave it a run from stop to full noise hole shot was excellent the boat lifted quickly and easily to the plain and accelerated to about 50 or 55kmh, which i feel is a bit to quick for the hull.
noise was my other main reason for the change the Yamahar is very very quite.
am i happy with the motor, u bet i am now only time can tell just how good the motor is

After all our discussion im glad that its worked out poly, how did you go without the other thing you were talking about adding? Im assuming the boat sat nicley in the water?

Good Stuff

Doubt very muck you've goten any more speed poly & yes the 4 banger wull get you up quicker you'll find the smoothness of the 4 stroke gives the illusion that you are going quicker thats all.

And since you can only gauge speed by feel you'll never know what the speed difference is you really needed a gps