www.iFourWinns.com

I have a 1994 Freedom 170 with a stock carb'ed 4.3. I am a pretty aggressive slalom skiier and am currently using a 15 pitch 3 blade stainless prop from Michigan Match. This works well at my altitude, with a pretty strong holeshot and adequate top end, topping out around 4300 rpms. All in all this is a pretty good slalom boat, with a reasonably flat wake due to its light weight. Picture of boat:



However, when I have a load in the boat, the holeshot suffers. I know I have a horsepower deficit compared to a DD towboat, but one thing my local boatstore guy suggested is trying a 4 blade prop.

Have any of you went from a 3 blade to a 4 blade (same pitch) and noticed a decent improvement in holeshot? I don't have a spare prop right now, so I don't really mind getting a 4 blade to try, but I thought I'd ask here first.

Thanks,

Allan

Hi Allan,

I have never tried a 4 blade prop, but any time you increase the number of blades (and lower the pitch to compensate) you will improve the hole shot. because you reduce the slip a little...

Just from your description it appears that you are a little over-propped. I don't have it at my fingertips but your engine probably has a rated WOT RPM of 4800.

If you're only getting 4300 at WOT you either have a tuning issue, your drive is the wrong ratio, your boat is way too heavy(water logged etc) or you're over propped. If it's running correctly, your tach could also be off as much as 500 RPM at WOT.

Mercury and Volvo both recommend propping any engine to produce close to max rpm at WOT with the boat loaded where you will typically operate in alt & load,

You could try a 14p 4 blade and probably improve the hole shot and not kill your top speed much but you need to know that your tach is correct.

(nice looking boat btw!)



Regards,

Rick

_________________
1987 Four Winns Liberator 211, formerly OMC 460 King Kobra powered, replaced in 2006 by a 1997 Mercruiser 454/Bravo III

The only thing I can add to Ricks post, see if your parts guy will demo a prop for you. Years ago, our dealer/parts guy let me demo a few props to help me decide which one I liked best.

_________________
2000 248 5.7L DP
'92, '94 SXI 750, '08 STX 15F, '12 Ultra LX 300
Videos

look at hillmarine.com great deals on 4 blade stainless props - know several people that have purchased from them & all have been very happy. You should be getting another 500 rpms @ wide open throttle. What elevation are you boating at?

You are getting adequate hole shot and top end with your current 3 blade because you are definately overpropped. If you change to get the higher RPM, holeshot will suffer, but RPM will increase. That won't solve your issue. You are on your own if you choose Hill Marine.

What outdrive do you have on your boat ?

_________________
One of 4 Previous (Sold) Boats:
2000 Four Winns 268 Vista

Current Boat: 2004 Chaparral 235 ssi cuddy

Um....methinks you may have it backwards Cap'n....(there's a little Cap'n Morgan in all of us!)

If you lower the pitch (which will give higher RPM)....it absolutely improves the hole shot.....It may reduce top end slightly or not at all........

_________________
1987 Four Winns Liberator 211, formerly OMC 460 King Kobra powered, replaced in 2006 by a 1997 Mercruiser 454/Bravo III

Agreed... It also gives you more acurate control with speed/rpm. More important than top end when you are skiing/tubing, etc. After all, how many times do you need that extra 4 mph, vice the added hole shot of getting that water-buffalo up on skis

_________________
Walt B
"Debt-Charged"
Black '07 H210SS
6.2L Bravo One turning a 21P HIFive
Wakeboard Tower with Perfect Pass Stargazer version
Missouri River; Kansas City, Mo.

shoot I went from a 3blade 21p to a 3 blade 19p and before I could get 40 mph at 4200 rpm now i can barely hit 30mph. The whole shot is good with ballast for wakeboarding etc. Not sure what going to a 19p with a 4 blade would do. I might do that.

_________________
Four winns 180 horizon

I doublechecked my WOT RPM the other day with the 3 blade 15 pitch SS prop. I misstated it earlier - I am hitting 4600 rpm, which puts me right in the middle of the recommended range of 4400-4800 rpm.

I'm pretty sure that my local store will let me demo a prop, so I guess I'll try a 4 blade 15 pitch and see what I think. Hopefully it is worth the expense; if not, I'll have a spare prop at least.

To answer a couple previous questions, I live at 4500 ft elevation and have the OMC Cobra drive.

Thanks for the replies,

Allan

If you're operating at 4500 MSL, you already have a built-in power loss.

You won't find a 15p 4 blade. It'll have to be either a 14 or a 16 (they usually only do even number pitch)

A 14 may work just fine for your application & at your alt.

_________________
1987 Four Winns Liberator 211, formerly OMC 460 King Kobra powered, replaced in 2006 by a 1997 Mercruiser 454/Bravo III

That's no longer true about even pitches.....iBoats seems to have a good selection and prices. Make sure you search for your set-up. I just used what I could surmise from the post. $120 isn't too expensive if you want to try a few different alum props and get the sizing right. Then again, it sounds like you've already nailed that down. $300 for a 4 blade SS is a good price as well.

http://boatpropellers.iboats.com/OMC/Any_HP_(1991-1994)_15.00-Pitch_Propellers/494/?rotation=Standard&session_id=689785455&cart_id=583125241

I do my business thru this place because they are local, and match iBoats prices....
http://midwestpropeller.com/

I just bought a High-Five through them..... they gave me "new" price for my trade in towards it. Can't beat that!

_________________
Walt B
"Debt-Charged"
Black '07 H210SS
6.2L Bravo One turning a 21P HIFive
Wakeboard Tower with Perfect Pass Stargazer version
Missouri River; Kansas City, Mo.

Yeah I think you may be right.

You just don't want to try to use the same pitch you have in a 3 blade or you might be somewhat over propped. (which is usually why a lower pitch 4 blade is recommended to replace a 3 blade)


If you're WOT RPM is correct (4300) , I would try a lower pitch 3 blade prop first. If you can get your WOT RPM up to rated max, I think you'll find that your holeshot improves and your top speed will not suffer.

_________________
1987 Four Winns Liberator 211, formerly OMC 460 King Kobra powered, replaced in 2006 by a 1997 Mercruiser 454/Bravo III

What about adding smart tabs? Have read some really good things about them

I really don't think "Smart Tabs" are all that "smart".....


They're just spring loaded tabs that cause drag and *some* lift at low speeds (at the expense of lower top speed)

I run my Bennett Sport Tabs all the way down when I pull a wake-board. They help keep the bow down.

If I want to run fast, I run them all the way up. At high speed they just produce a LOT of drag. Spring loaded tabs would cause drag at high speeds but not do much else......

_________________
1987 Four Winns Liberator 211, formerly OMC 460 King Kobra powered, replaced in 2006 by a 1997 Mercruiser 454/Bravo III

I have never heard anything good about them.

I ditto Ricks thoughts.

_________________
2000 248 5.7L DP
'92, '94 SXI 750, '08 STX 15F, '12 Ultra LX 300
Videos