changing from stainless to aluminium questions

[aerobat]

hey gents ! when changing from a SS to an aluminium prop , how is the difference in WOT when pitch stays the same ?

i currently have a laser II in 14 1/4 x 17 on my 21 footer cabinboat . the engine ( volvo 3.0 GS ) struggles to rev higher than 3900 rpm in this config so i want to reprop- basicly with a stainless in 15 pitch .

but after reading about very good results about modern aluminium propellers in my power range i take into consideration the solas amita 3 aluminium.

options would be a 15x15 or a 14,8 x17 .

i would like to get my rpm to about 4600 and when possible to at least keep my current topspeed. ( about 28 mph )

when we focus on aluminium - will a 17 pitch aluminium bring up WOT rpm enough in comarision to the current 17pitch laser II or should i go also here for a 15 pitch alu ?

thanks for inputs !

 

[Bondo]

Re: changing from stainless to aluminium questions

struggles to rev higher than 3900 rpm in this config
i would like to get my rpm to about 4600

Ayuh,.... I really doubt just goin' Aluminum will do what ya need,...

Others who know more will have a Better idea,...

Yer lookin' for 700 rpms...

Is the outdrive of the proper ratio,..??

Is the hull severely overloaded,..??

 

[aerobat]

Re: changing from stainless to aluminium questions

ahoi bond !

drive is a 1.97 SX , 28mph at 3900 rpm with this ratio and 17 pitch seem also to be "correct"

boat is roughly 3300 lbs dry , about 3800 lbs with fuel and 2-3 persons . like said a 21feet cabin cruiser .

yes, i,m looking for 700 rpm,s - maybe a little less, the correct rev range is 4200-4600.

what do you think ?

 

[trendsetter240]

Re: changing from stainless to aluminium questions

It's unlikely that switching from your current prop to a 17p aluminum would have the effect you are looking for.

The 15p prop you mentioned would probably bring your rpms up 400 or so from the current SS laser. Pushing a 21ft cabin cruiser is a lot to ask out of a 3.0. You are certainly over propped and the solas 3 is a good, inexpensive option to improve performance and get your motor into the correct range.

 

[jestor68]

Re: changing from stainless to aluminium questions

I suggest the Solas Rubex 15 X 15 to pick up about 500 rpm and get a top speed of 30-32 mph.

 

[dan02gt]

Re: changing from stainless to aluminium questions

I suggest the Solas Rubex 15 X 15 to pick up about 500 rpm and get a top speed of 30-32 mph.

+1

The Laser II is not even close to the right prop for that boat. It's made for light boats with a good amount of HP (like a bass boat).

 

[tazrig]

Re: changing from stainless to aluminium questions

Apples to apples, just switching from a stainless to an aluminum prop won't help you out that much. A 3.0 for a 21'? Was that the original engine to the boat or a re-power. That seems awful small.

 

[aerobat]

Re: changing from stainless to aluminium questions

thanks very much for the very helpful inputs gents !

one more question : is there a difference between solas amita and solas rubex beyond the amita seems to have a fixed and the rubex an interchangable hub system ? the amita is easier to get in germany.

 

[trendsetter240]

Re: changing from stainless to aluminium questions

thanks very much for the very helpful inputs gents !

one more question : is there a difference between solas amita and solas rubex beyond the amita seems to have a fixed and the rubex an interchangable hub system ? the amita is easier to get in germany.

The only difference is the hub.

 

[aerobat]

Re: changing from stainless to aluminium questions

thanks !

my original idea was a michigan wheel stainless in 14 3/8 x15 but now the solas amita 15x15 seems to be a serious and more cost effective option.

awesome forum members !

 

[aerobat]

Re: changing from stainless to aluminium questions

please excuse , one more question : in case of the amita with a fixed hub for the volvo sx ( 19 teeth) am i correct that i do not need any extra parts like e.g thrust washers, spacers etc , so i need to buy just the prop and it works plug and play ?

 

[jestor68]

Re: changing from stainless to aluminium questions

please excuse , one more question : in case of the amita with a fixed hub for the volvo sx ( 19 teeth) am i correct that i do not need any extra parts like e.g thrust washers, spacers etc , so i need to buy just the prop and it works plug and play ?

As there is no hardware shown for it in the prop section, I assume it to be mount and play using the original parts.

 

[phillnjack2]

Re: changing from stainless to aluminium questions

a 3.0 litre engine is not too small for a 21 ft boat.

But a 3 litre volvo GS is normaly only around 130hp, its a very detuned engine.
you need to ask around a few people with the same engine what their performance is and what size prop they use to get an
idea of what to expect from yours.

Get the engine compression checked with a different tacho and make sure everything on your engine is in tip top condition.
if you have never got high revs then maybe the tacho is wrong or the prop is way too big. but i would of thought a 13 diameter
would of been fitted with a 15 pitch on that set up.

Now if other people are getting same slow speed then look around and get a much better set of carbs for the engine.
those 3 litre volvo's can be taken way over 200hp with decent carbs fitted to them.
or if its fuel injected then get it chipped up and ask for more torque at mid to high revs.


phill

 

[Bondo]

Re: changing from stainless to aluminium questions

a 3.0 litre engine is not too small for a 21 ft boat.

But a 3 litre volvo GS is normaly only around 130hp, its a very detuned engine.
you need to ask around a few people with the same engine what their performance is and what size prop they use to get an
idea of what to expect from yours.

Get the engine compression checked with a different tacho and make sure everything on your engine is in tip top condition.
if you have never got high revs then maybe the tacho is wrong or the prop is way too big. but i would of thought a 13 diameter
would of been fitted with a 15 pitch on that set up.

Now if other people are getting same slow speed then look around and get a much better set of carbs for the engine.
those 3 litre volvo's can be taken way over 200hp with decent carbs fitted to them.
or if its fuel injected then get it chipped up and ask for more torque at mid to high revs.


phill

Ayuh,.... I question those 2 thoughts Phill,....

The 3.0l GM motor, in No way will pull 200 hp, at rpms usable in a boat...

'n while I ain't big on Volvo drives, I have tried puttin' a 13" diameter prop on a Mercruiser,...
It Don't Work,....
The props body is too small a diameter, 'n it blows out....
Ventilating with the exhaust gases runnin' Outside the prop, insteada down the center...

 

[aerobat]

Re: changing from stainless to aluminium questions

i finally bought a turning point hustler aluminium in 15 1/4x15 and will test it out as soon as the boating season finally begins in my marina. hopefully i get now good results !

 

[steelespike]

Re: changing from stainless to aluminium questions

ahoi bond !

drive is a 1.97 SX , 28mph at 3900 rpm with this ratio and 17 pitch seem also to be "correct"

boat is roughly 3300 lbs dry , about 3800 lbs with fuel and 2-3 persons . like said a 21feet cabin cruiser .

yes, i,m looking for 700 rpm,s - maybe a little less, the correct rev range is 4200-4600.

what do you think ?

Present numbers get a respectable 12% slip a 15" prop if it can get 4300 and 10% slip results are 27.9.
It appears the Solas 15 is a good gamble.

 

[aerobat]

Re: changing from stainless to aluminium questions

thanks steelespike - like said , the prop i finally bought is the hustler 15 pitch , i keep you informed how it works on my boat !

 

[aerobat]

Re: changing from stainless to aluminium questions

ok gents, after a long winter i today put my boat into water and test drove the new prop , its a turning point hustler aluminium 15 1/4 X 15 now.

the relusts are :

4300 rpm and 30 mph gps , but with full gas tank and three adults, lightweight i can maybe hit 4400 rpm and 31 mph, in any case the engine revs correctly now and i,m happy with the results !

thank you very much for your hint in choosing the right pitch for my boat !