Prop problem !!!!!

[tigerhack]

i have a 15 x 17 aluminum prop whitch is damage i now have a stainless steel 14 1/2 x 19 that i wish to install, the question is will i get a better performance, i am looking for a quicker plain off ,and of course faster speed, better fuel economy (is the prop iam getting better ?) alpha 1 gen2 5.7 litre mercrusier 350. engine.

 

[TilliamWe]

Re: Prop problem !!!!!

Dream a little dream there tiger. Not only won't one prop do everything you are wishing for, it's hard for use to know how that 19 will do, cause we don't know how the 17 performs.
In basic terms, if your 17 was turning at the very top end of the WOT RPM range, that 19 will turn in the very bottom of the WOT RPM range. It will also be slower out of the hole, with a slower time to plane. It may provide a faster top end. I doubt economy will change much at all.
If your 17 was turning at the low end of the WOT RPM range, the 19 will not be a good prop at all. It will be a dog out of the hole, really slow to plane, and it will lug your rngine and not turn a high enough WOT RPM, which can damage you engine.
Good luck.

 

[Don S]

Re: Prop problem !!!!!

Moving to Prop Fourm

 

[tigerhack]

Re: Prop problem !!!!!

Dream a little dream there tiger. Not only won't one prop do everything you are wishing for, it's hard for use to know how that 19 will do, cause we don't know how the 17 performs.
In basic terms, if your 17 was turning at the very top end of the WOT RPM range, that 19 will turn in the very bottom of the WOT RPM range. It will also be slower out of the hole, with a slower time to plane. It may provide a faster top end. I doubt economy will change much at all.
If your 17 was turning at the low end of the WOT RPM range, the 19 will not be a good prop at all. It will be a dog out of the hole, really slow to plane, and it will lug your rngine and not turn a high enough WOT RPM, which can damage you engine.
Good luck.

with my now damage 15 x 17 prop i have to go full throttle before i could plane off full blast the nose of the boat always in the air, i want to aviod that i want to at least get out of the hole fast , one of my friends say to send my friends to the front it will plane faster ,well we are dealing with a 25 foot monster here with a lot of load .. the thing is i only have this stainless 14 1/2 x 19 handy if not i will just wait and buy a good one,i still need to know if it will do me good.

 

[Silvertip]

Re: Prop problem !!!!!

Until you provide the answers to the performance question with the existing prop we can't tell you how the 19 will perform.

Tell us what the wide open throttle rpm and speed you observed with the current prop (preferably before it was damaged).

If you can't tell us that, we can't help you.

Going up in pitch might increase speed but will hurt hole shot.
Going down in pitch increases hole shot but will hurt top speed.
Neither will change fuel economy any significant amount.

 

[walleyehed]

Re: Prop problem !!!!!

The 19 is not gong to be a good option on that size of rig....I would be more inclined to look for a 16P 4-bld ss for the stern-lift with no loss of hole-shot

 

[Bondo]

Re: Prop problem !!!!!

with my now damage 15 x 17 prop i have to go full throttle before i could plane off full blast the nose of the boat always in the air, i want to aviod that i want to at least get out of the hole fast , one of my friends say to send my friends to the front it will plane faster ,well we are dealing with a 25 foot monster here with a lot of load ..

Ayuh,.........

A set of Trim Tabs might Help,.....
Going to a Larger Prop Definitely Won't........

 

[Don S]

Re: Prop problem !!!!!

You are trimming the drive all the way down when taking off aren't you? That will help bring the nose down. Then after the nose comes down and the speed goes up, start trimming up till you get to the best speed an rpm.

 

[tigerhack]

Re: Prop problem !!!!!

You are trimming the drive all the way down when taking off aren't you? That will help bring the nose down. Then after the nose comes down and the speed goes up, start trimming up till you get to the best speed an rpm.

Drive is always trim down.

 

[tigerhack]

Re: Prop problem !!!!!

Until you provide the answers to the performance question with the existing prop we can't tell you how the 19 will perform.

Tell us what the wide open throttle rpm and speed you observed with the current prop (preferably before it was damaged).

If you can't tell us that, we can't help you.

Going up in pitch might increase speed but will hurt hole shot.
Going down in pitch increases hole shot but will hurt top speed.
Neither will change fuel economy any significant amount.

my tach dont work , my speedo meter dont work so i cant tell .

 

[Don S]

Re: Prop problem !!!!!

If you don't have a tach, and you don't use trim, then you nor anyone else can even guess what you'll need.
WOT rpm is the main ingrediant in determining prop size (dia and/or pitch).
Your best bet now is to get the same size prop or get yours fixed. Get the tach fixed, learn how to use the trim and see what your WOT rpm is. Then come back with the results.

 

[tigerhack]

Re: Prop problem !!!!!

If you don't have a tach, and you don't use trim, then you nor anyone else can even guess what you'll need.
WOT rpm is the main ingrediant in determining prop size (dia and/or pitch).
Your best bet now is to get the same size prop or get yours fixed. Get the tach fixed, learn how to use the trim and see what your WOT rpm is. Then come back with the results.

i was just asking will i do any damage , and what are the advantages , is it worth trying , 1/2 inch down grade with diameter , and 2 inch upgrade with pitch , isnt there some kind of equivalent in this ?

 

[TilliamWe]

Re: Prop problem !!!!!

With the way you describe the 17 prior to it being damaged, that 19 will be worse in all catagories. If it's just a little time, sure, try it. But it won't be better.
You have so many other things to do before you can fine tune your prop. Good luck fixing all the things that need fixing.

 

[oops!]

Re: Prop problem !!!!!

hey tiger.

your question has been asked before. hit search.

however.

unless you have a tach and reliable mph readings (gps), anything you do is just a guess. how are u gonna know if one prop gives gives you .5 mph difference.
(thats a lot).

you need some prop understanding basics.

look under a post called 5 blade prop.
it will give you a very basic understanding of what to look for in a prop speed.

very basic.... mabe the guys here can suggest another more in depth post about prop vs rpm vs speed, then go to it.

read... learn....add the nessary instruments to measure.... then add trim
then....we can got you outta the hole, on plane..and ripping thru the water...with the best of all three worlds possible

just a note....you can only acheive a balance of all three....you must give up somthing to get more of one than the other.

let us know how its going!!!!
everyone here is eager to help you.

cheers
oops

 

[tigerhack]

Re: Prop problem !!!!!

hey tiger.

your question has been asked before. hit search.

however.

unless you have a tach and reliable mph readings (gps), anything you do is just a guess. how are u gonna know if one prop gives gives you .5 mph difference.
(thats a lot).

you need some prop understanding basics.

look under a post called 5 blade prop.
it will give you a very basic understanding of what to look for in a prop speed.

very basic.... mabe the guys here can suggest another more in depth post about prop vs rpm vs speed, then go to it.

read... learn....add the nessary instruments to measure.... then add trim
then....we can got you outta the hole, on plane..and ripping thru the water...with the best of all three worlds possible

just a note....you can only acheive a balance of all three....you must give up somthing to get more of one than the other.

let us know how its going!!!!
everyone here is eager to help you.

cheers
oops

thanks i understand that , but i love to test things out, what i have heard from the guys here on the island is the wider prop take you out of the hole faster, and more pitch give you more speed after plane off . is it true ?

 

[oops!]

Re: Prop problem !!!!!

to my VERY limited knowelage.
wider prop....more bite....more hole

steeper pitch....more go...less revs

cupping gives a better bite too

 

[tigerhack]

Re: Prop problem !!!!!

Dont know if this is forbidden here but here is a link that i found that interst me a lot . Doh no link ,no Problem Mon. sorry .

 

[oops!]

Re: Prop problem !!!!!

but u still GOTTA have a tach..
was just reading up a few.. u asked don if you can do damage.

you can kill it.

keep in mind, you almost gotta be a idiot to do it, you can hear when your over revving.

but you gotta have the instruments to know the truth...any thing else is just a guess.

oops

 

[tigerhack]

Re: Prop problem !!!!!

to my VERY limited knowelage.
wider prop....more bite....more hole

steeper pitch....more go...less revs

cupping gives a better bite too[/QUOTE

good to know, by the way i try to fit the new prop on and it start to bind , like i am missing a spacer or something , do these props normally comes with there own fittings ?

 

[oops!]

Re: Prop problem !!!!!

i think if you try to go to different styles/manufacturers there might be some changes....my prop guys have had to play with adding some stuff to change props...i wasnt sure what was going on but i felt the guy was just tring to give me a story so he could sell me a prop.

btw. what island?