Prop Question... Bayliner BR185

[1tman1]

Hi Team
Question on compatibility/fit/etc please.
Bayliner BR185 with 4.3 V6 Mercruiser. Currently running an Alloy 21P 14.5" OE prop.
Hard work getting up on plane at slow speeds towing kids on Tube.
Wondering if a Mirage Plus 17P 15.5" Prop will work/fit/suit our needs?
Boat used mostly for Tubing and Trolling. With some Wakeboarding for the Kids, and the Very occasional Ski for Dad (when the body holds up!)
Not too fussed on top end speed. Boat generally loaded with 2 Adults & 2-3 kids.
Current Prop is in pretty bad shape, so looking to update and go Stainless.
And if the Mirage Plus mentioned above isn't ideal, what would be?
Cheers

 

[jimmbo]

Before you go buying Props, a few questions
1) how long have you owned this boat?
2) What condition is the Motor in, as in: Compression Numbers, Spark at all Cylinders, Spark Plugs?
3) What WOT Rpm are you getting with the current Prop?
4) Do you know the WOT Rpm range for that Motor?

If you are the One that banged up the Current Prop, I would be very leery/cautious about putting a Stainless on.

 

[1tman1]

Before you go buying Props, a few questions
1) how long have you owned this boat?
2) What condition is the Motor in, as in: Compression Numbers, Spark at all Cylinders, Spark Plugs?
3) What WOT Rpm are you getting with the current Prop?
4) Do you know the WOT Rpm range for that Motor?

If you are the One that banged up the Current Prop, I would be very leery/cautious about putting a Stainless on.

Have owned the boat for 14 years, it's a 2006.
Motor in good condition, Compression good, Spark good etc. Serviced regularly.
WOT with current is around 4600. WOT range is 4400-4800
Yes, I was responsible for current condition of the prop... However the conditions that lead to that condition no longer exist... Hence part of the reason behind looking to replace.

 

[jimmbo]

Did the WOT Rpm Change as the Prop got Massaged? You are propped pretty close to Optimum. Dropping 4" in Pitch will unload the Engine way too much, and increase the WOT Rpms to about 5400.
Try to find a 20" Prop, that should give you a couple of Hundred more Rpm. That assumption is based on the New Prop being of the same Brand and Model. A switch to a different Brand and/or Prop Model, all bets are off.
As for Stainless... Be prepared to be Underwhelmed. I have been playing with Stainless Props for over 45yrs. Unless changes in Rigging are made, and a switch to actual Performance Props, there usually minimal Changes to Top End, but in instances the SS may have a better Grip on the Water

 

[1tman1]

Did the WOT Rpm Change as the Prop got Massaged? You are propped pretty close to Optimum. Dropping 4" in Pitch will unload the Engine way too much, and increase the WOT Rpms to about 5400.
Try to find a 20" Prop, that should give you a couple of Hundred more Rpm. That assumption is based on the New Prop being of the same Brand and Model. A switch to a different Brand and/or Prop Model, all bets are off.
As for Stainless... Be prepared to be Underwhelmed. I have been playing with Stainless Props for over 45yrs. Unless changes in Rigging are made, and a switch to actual Performance Props, there usually minimal Changes to Top End, but in instances the SS may have a better Grip on the Water

Thanks for that... Will going up in size from 14.5" to 15.5" somewhat offset the reduction in Pitch? Or not enough.
The current prop has been getting massaged for a while, so couldnt honestly answer if the rpm changed or not... I will recheck the WOT in a week or so when I'm back with the boat.

 

[jimmbo]

Diameter doesn't have as much effect as Pitch, however Pitch and Dia are only 2 Variables when it comes to Props, though a lot of Props, but not all, do increase in Diameter as Pitch drops. Blade Area, Flat or Progressive Pitch, Cup, and Rake are other things that come into Play. That is one of the Reasons I stated that switching Brands/Models of Props quite often becomes a Crapshoot

 

[jlh3rd]

you are getting good advise, especially since"propping" can get expensive
Important question, is your WOT@4600 with a loaded boat or a number with just you. On paper, the basics are: Reducing a blade count, decreasing pitch, and decreasing diameter .....everything else equal ( including manufacturer and prop material) increase rpms. Throw in different blade designs, cupping, etc. as mentioned....all bets and calculations are off.
I have Mercs 4-14x14, 3-16x13, and a Solas 3-15.5x13. All give the same #'s . 5800 rpms@WOT. 25.5-26 mph. Me by myself, pontoon. Motor range is 5-6000rpm.
I had to get a merc 3-16x12 so I could pull tubes and not bog. It gave me 6100+ rpm @WOT, maybe 24mph....but 22.5+ @6000 rpm. But it kept me in the upper rpm range loaded...56-5700@WOT rpm instead of 5300 with the other props.
Fwiw...props are not magical.

 

[Scott06]

Have owned the boat for 14 years, it's a 2006.
Motor in good condition, Compression good, Spark good etc. Serviced regularly.
WOT with current is around 4600. WOT range is 4400-4800
Yes, I was responsible for current condition of the prop... However the conditions that lead to that condition no longer exist... Hence part of the reason behind looking to replace.

Go down to a 19” you may have to watch wot rpm lightly loaded. Alternatively a 4 blade 18” pitch like Michigan vortex can do what u want.

I have run 4 blades on my last two boats for same reasons you reference, loaded down water sports. I personally prefer 4 blades for holeshot and stern lift when heavily loaded.

 

[ESGWheel]

Concur with Scott > go to a 4 bladed. I had a similar use / profile as you when bought the new to me boat (Larson 228 LXi) some years ago. Came with a 3 bladed but no hole shot & sluggish to plane out and WOT was shy of spec at abt 4800 vs 5000 (two people). Talked to the local marina and they recommended going a 4 blade. I got lucky as they nailed it first time out. Over the years the kids had a lot of fun including single ski and I now hit 5k WOT. Also recommended Al vs. SS for cost and just in case need to try out a couple of different options.

Also talk to the folks at the marina and fellow boaters at the dock with similar boats. Can be a lot of good info there to help you select. And the marina may even be willing to let you borrow a prop or two to get it dialed in or check out the used props they have on consignment. And you may be able to put the ‘trial’ props you had to buy but did not work out on commission at your marina, so not a complete loss.

Even if must buy a few to get it dialed in, do it. Its well worth it due to the short time boating happens and the speed at which the kids grow up.

 

[1tman1]

Thanks for all the advice team... Going to recheck WOT rpm in a week or so when back with the boat... And will go from there...
Appreciate the advice. And will come back with update when there is one.
Cheers