decide me a prop

[tkrrox]

i have a 1989 sea ray 180BR with a mercury 135...i just recently bought this boat...when i bought it there was a 19p 3blade SS on it and after looking it up it was factory...

the boat was only getting 5200 fully trimmed and 46.4 on the gps...so i bought a 17p aluminum 3blade solas from this site and am getting 5600 fully trimmed, but on 42.6 on the gps...the 17 does feel like it pulls better but no by much.

so the million dollar question...with both props i am having issues with blow out (cavitation) while turning, so i am thinking a 4blade...so do i buy a 19p or a 17p and which type? you guys like the solas or quicksilver?

thank you
tk

 

[steelespike]

Re: decide me a prop

I would say your original prop was doing very well except for the rpm.
Some very quick math if its right indicates about 42 mph at 5200
and thats disgegarding slip, hull design etc.A 19 at 5600 would produce about 44.
Also the 17 appears to produce
38 at 5600.This seems to indicate the tach may be off. Indicating less than actual rpm
Again these figure disregard slip, drag, etc.
You need to verify the tach maybe borrow or rent a shop tach from your marina.
An aluminum prop will seldom perform like a ss prop.
Also when decreasing pitch you might lose speed.
Blow out in turns is normal for a boat setup for maximum performance.
The higher the motor the less drag but more sinsitive to venting.
Usually if you trim down in a turn it will reduce venting/blowout.
How severe of a turn produces ventilation?

 

[tkrrox]

Re: decide me a prop

it blows out around 60* or sharper. that's why i was thinking a 4 blade might help

i don't think this boat is set up for performance...it is completely stock.

how much of a difference is there between a SS and AL, i just thought it was regarding flex and with a little HP motor like mine it wasn't worth spending 3X more for the SS

 

[QC]

Re: decide me a prop

after looking it up it was factory...

i don't think this boat is set up for performance...it is completely stock

Although there are some OB packages that are put together at the factory, generally speaking there is not a fixed "stock" boat; especially OBs, and it may not be right even then. Prop selection is one of many things that owners and dealers change and they may even modify the existing ones. Motor height is another and if the dealer rigged the boat who knows where it ends up.

Are you trimming down (in) for turns? It is good idea to try trimming all the way down as you enter a turn, and then start to trim up as you exit and start to accelerate. Can make a huge difference. And then of course prop design, weight balance, hull condition (shale can be off), accessories etc. cna all have influence.

Need to verify that tach, as SS has suggested and remember that prop selection is voodoo and stock doesn't mean much. Good luck!

 

[steelespike]

Re: decide me a prop

it blows out around 60* or sharper. that's why i was thinking a 4 blade might help

i don't think this boat is set up for performance...it is completely stock.

how much of a difference is there between a SS and AL, i just thought it was regarding flex and with a little HP motor like mine it wasn't worth spending 3X more for the SS

When you change props in the same material same brand, same model different pitch results are fairly predictable.When changing material, brand, model and pitch predictability goes out the window.When going from a propertly running ss to an unknown al prop about the only thing you can predict is the al will not perform as well as the ss.

When I said set up for maximum performance I meant best performance,most efficient operation. etc.Technically I think a ss prop is probably factory but not standard.
Also prop selection on a new motor would depend on its application,type and size of boat.
The dealer would make the initial prop selection based on the boat and the buyers activities and material preference.
Any basically stock family boat with your "small" motor
that approaches close to 50 mph is dialed in very well.Getting to 50 with a boat thats not
loaded with brute hp is really tough, gettng over 50 is much harder.