20.5 Ft Bowrider Prop Choice

[akcooper9]

Its everyone's favorite question...what prop do for my boat...haha

Anyways, I have an 03 VIP Vixen XL 2096 (weight is right around 3500lbs with fuel) 20.5ft Bowrider with a 5.0 MPI and alpha 1 gen 2 with a Mercury Mirage 48-13702 21P prop. Boat flat out hauls the mail with GPS verified speed of 60 MPH with full tank of fuel and family of 4 on board.

Been thinking of changing things up for some more low end torque. What are your thoughts suggestions. Would like to stay with SS but which brand? 3 vs 4? ETC I have no idea where to start.

 

[Scott Danforth]

you can drop down to a 19P 3-blade for more low end grunt, or a 17-18P 4-blade. I myself like the stainless props. the best thing would be to see if your local prop guy has a bunch of props to try.

 

[Tail_Gunner]

Here try the lower question's to get a more accurate picture and better reuslt's......Nice boat. Can you post a pic of your transom hull area it appears to have a pad or a notch..

Read This First!! December 22nd, 2008, 10:11 AM

ESSENTIAL DATA REQUIRED
When posting a question about propellers, you cannot get a reasonable answer unless you provide the following information in your post: Items 1-4 are essential for meaningful response to most questions.
1) Performance issue you are trying to correct........................................... ........................................
2) Current prop manufacturer, model, aluminum or stainless as a minimum.
3) Current prop diameter and pitch (required).
4) Wide open throttle....... RPM........ and speed with an average load (very helpful)
5) Engine/drive make, model, year, and HP,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, ,....................................... Post your gearing on the drive its on a metal stamp on mid of the leg
6) Boat make model, year, length and weight

The below link would be a much more thorough list of data to provide if you're looking for detailed performance numbers,
http://forums.iboats.com/prop-questi...ml#post2336620


Ahh got it...pad and a small v interesting gearing is all that is needed.

 

[akcooper9]

Here is a shot of the steps in the hull

 

[akcooper9]

Ahh got it...pad and a small v interesting gearing is all that is needed.

Can you help me understand what you are asking? Im not sure on the gearing. New it was 1.62 but the PO had a reman put on after sheering the gears. Ill need to check when I get home on that one.

I do know that going down a size to say a 19 will give me more low end but there are way to many 3 blade 19 props to pick from...how do you know?

 

[Tail_Gunner]

Can you help me understand what you are asking? Im not sure on the gearing. Ill need to check when I get home on that one.

I do know that going down a size to say a 19 will give me more low end but there are way to many 3 blade 19 props to pick from...how do you know?

Your performance is very good with that mirage...what is needed.. is the final gearing of the outdrive.. such as 1.98...1.8...1.5...1.47 etc. That info will display... how much slip the prop is doing.... and how effecient your hull is..With a boat full of people you want the boat engine to run at 5000 rpm or close to that and along those lines how many people do you want to run in the boat and how many people were in the boat when it hit 60 mph and what was the rpm level...This will all make sense as it progress's

Here's part of a example..your hull bottom question...The boat is 20'...does 60 mph..probaly a 270 hp engine that's pretty stout of a smaller boat. On a deep v doing 60 chine walk can come into play so a high lift 4 blade might not be the best type but you have a pad which should eliminate that so a high lift 4 blade would be very much in favor...read lot's of midrange punch and lifting the hull which lends to less drag and very good top end speed.

 

[akcooper9]

TG see my edit above. Original drive ratio was 1.62 but ill need to double check the reman if its on there.

Also post 4/5 sound like what im looking to do. http://forums.iboats.com/forum/gene...s-and-topics/8588988-5-0-push-a-21-pitch-prop

 

[Tail_Gunner]

TG see my edit above. Original drive ratio was 1.62 but ill need to double check the reman if its on there.

Also post 4/5 sound like what im looking to do. http://forums.iboats.com/forum/gener...-21-pitch-prop

Not even on the same planet...you have a mpi engine and given the fact its doing 60 im sure its 270 hp vs 200 on a old carbed 5.0...in additon the vip has much faster hull and a pad...two differnt animals...and thens theres the drive ratio they could be driving a 1.5 ratio which is pretty std for a small v8

 

[akcooper9]

Go home and double check the gear ratio on the reman and it appears to be a 1.62 (the reman has a part number of 861063R10)

Now on to props. So a 19 4 Blade is what we are thinking? Would a 3 be a waste?

 

[Tail_Gunner]

Well maybe or not..... there's a few thing's that arnt quite right and that is quite nomal for example 21p prop at 4900 rpm with a 1.62 gear ratio nets 60 mph in therory and yet you have 60 with a boat load of four..so we just dig a bit deeper and find out what's what.This happen's all the time by the way..... On a side note a 1.47 nets 9% which could happen i guess.

 

[akcooper9]

The boat with 4 people is really only my wife and I along with a 1 year old and 3 year old

I dont think 60MPH is what I want or need. I mean hey I like to get on it once in a while but 50-55 is plenty.

What other information do y'all need from me? Been reading alot on the Rev 4 but still cant make any sense of all the options.

 

[Tail_Gunner]

This is simple you take a ride on the boat.... use gps to find your top speed at wide open throttle...read the tach when the boat reaches top speed and wide open throttle and note the rpm....post your gearing on the drive. In doing that one can determine if the propeller is geared right for the boat engine combo...that is also commonly stated as...."Pitch" . In doing that your overall gearing... power..... and hull dynamic's come together and work as one...the engine will not be over worked shorting it's life...maxium fuel economy and speed will be reached they work as one...and your will have spent your money well. It can be quite frustrating to spend anywhere from 3/500 dollars and end up with the wrong prop.

As to brands there are quite a few out there and they have different characteristics some are stern lifter's some are bow lifter's some are overall lifter's some are 3 blade read speed some a 4 blade read midrange power...the list is endless. In the end they all will work there are some that shine and some that dont but they work. Its difficult to or short sided to just do WAG...wild a@@ guess but that can be done.....I assume when your at full power and top speed you dont hear a very mild very brief engine miss it happens for a micro second of time yet its still there.

Your gearing is quite important here if its 1.62 then there's something off.... Now if it is 1.5 then it could be accurate and a WAG could be in order...Its up to you it's your money.

http://www.go-fast.com/Prop_Slip_Calculator.htm

 

[akcooper9]

I found a Mirage Plus 19P for cheap locally, would just going from a 21P down to a 19P be worth it? Before looking at a 4 blader?

 

[SkiDad]

i think that 3 blade would be fine - you just have to watch your rpm but will make huge difference for water sports

 

[Tail_Gunner]

The mirage prop is a very good prop and that prop should pull that combo like a tractor.

 

[akcooper9]

Doing some more looking at the part number on the prop and it reads QUICKSILVER 48-13700 A40 19P

Is it a mirage and not a mirage plus? The A40 does mean its a pressed in hub but can be pressed out and converted to flo torq correct?

Think it is still worth picking up for 100?

 

[akcooper9]

Here are two more shots of the hub

 

[SkiDad]

I have no idea if you can switch the hub, but if it fits as is why would you ? I think that's a great buy.

 

[akcooper9]

I picked up the prop today. As soon as it warms up a bit more, Ill hit the lake for some testing. I want to nail down my current set up RPMs and then try the new prop.

I have to admit, I was surprised how heavy SS props are.

 

[Tail_Gunner]

I picked up the prop today. As soon as it warms up a bit more, Ill hit the lake for some testing. I want to nail down my current set up RPMs and then try the new prop.

I have to admit, I was surprised how heavy SS props are.

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