determining which prop to buy

MASTER Brian

Senior Chief Petty Officer
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I currently have a 3 blade prop on my 17' Ranger 373 with an E-150XP motor. The boat seems to get up and go pretty well, but when I put a skier or tube behind it, it seems to lag just a bit.

Would changing to a 4-blade prop help and how do I decide what I need to go with?

I know you probably need more info, but I don't know what info to provide.

Thanks
 

Barnacle_Bill

Admiral
Joined
Feb 8, 2004
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6,469
Re: determining which prop to buy

A 4 bladed prop will give you a better hole shot but need to know what size prop you have now and the RPMs at WOT.
 

MASTER Brian

Senior Chief Petty Officer
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Re: determining which prop to buy

In order to determine RPM's at WOT, is that with the boat planed all the way up or not?
 

MASTER Brian

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Re: determining which prop to buy

WOT= Wide Open Throttle

I realize that, I just don't know if that means motor trimmed all the way up or not. I am guessing it does, but I don't like to work off of assumptions.
 

MASTER Brian

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Re: determining which prop to buy

This is what I came up with:

I ran the boat on pretty smooth water, but I had 6 people on board. 3 adults and 3 children. I don't know if that invalidates my figures out or not, but that is what I would have on the boat on a normal outing, when skiing. I was at the maximum on # of people and probably close to max on weight of those people.

I ran it with throttle all the way open and I trimmed the motor up as high as I felt comfortable doing, as my trim gauge, not sure of it's complete accuracy, was all the way up and RPM's seemed to be leveling out.

I had 4800 RPMs. Probably would go higher, if there were less people on board, but like I said, that's about what I would have weight wise on a normal outing where there would be skiing involved. When I go fishing, there's at most 3, but probably 2/3 of the weight I had above.

My current setup is a 14 1/2" DIA, 3 blade 24" Pitch SST RAKER prop stainless prop.

The engines manual states, that should run the boat at about 55-67 MPH. Prior to rebuilding the motor about two years ago, I know I had the boat at 57mph with a GPS, and I thought RPM's were about 5000rpm at that time, with me and 1 person on board. Felt like I had room to go. I didn't have the GPS's hooked up this past weekend, so not sure of mph, and I know that doesn't really matter.

The manual for the motor, states Full Throttle Operating Range to be between 4500rpm's and 5500rpm's.

I am looking for a prop that will pull a slalom skiier out of the water. With my current prop, the motor really bogs down, when I try to pull a skiier up. Without a skiier, my boat gets on plane fast and seems to have great hole shot. The boat is an 18' Ranger 373V with an Evenrude XP 150.

Thanks,
 

K.P.

Seaman Apprentice
Joined
May 29, 2008
Messages
39
Re: determining which prop to buy

WOW, six people on a bass boat? I guess my first suggestion would be to trade it in for a fish and ski type boat that is a little more appropriate for your needs. Possibly a little safer for those full load outings too!

Reaching 4800 RPM with the full load of people you describe tells me your boat is probably propped about as well as it could possibly be. I'd guess your hitting close to the Max RPM with just one person aboard and a light load of fuel.

It will be hard to find ONE prop that will perform well with a full load and pulling skiiers/tubers, plus not over rev the motor when only a couple fishermen on board. I have two props for this purpose. One for full loads, and one for normal loads.

You have to realize your hull is not really designed for planing well with so much weight on board so it's best to get that sucker turning a higher RPM with the full load. My suggestion is to buy another SST Raker prop that is as low as 21 pitch but no more than 22 pitch for those full load boating days. If you switch to another brand and type of prop, you may not achieve what you are seeking because RPM's change so greatly with different types and brands of props.
 

MASTER Brian

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Re: determining which prop to buy

WOW, six people on a bass boat? I guess my first suggestion would be to trade it in for a fish and ski type boat that is a little more appropriate for your needs. Possibly a little safer for those full load outings too!
This is a fish and ski type of boat. And it is designed to handle 6 people 750lbs, which isn't including motor, gas, etc....

Reaching 4800 RPM with the full load of people you describe tells me your boat is probably propped about as well as it could possibly be. I'd guess your hitting close to the Max RPM with just one person aboard and a light load of fuel.
I suppose I could test that, but I rarely ever go WOT.

It will be hard to find ONE prop that will perform well with a full load and pulling skiiers/tubers, plus not over rev the motor when only a couple fishermen on board. I have two props for this purpose. One for full loads, and one for normal loads.
I know I probably won't find one that does both, but I'd like to find one that works for the play time, as that's really were this boat gets used the most. If I want to go fast, I can always change back to my current prop.

You have to realize your hull is not really designed for planing well with so much weight on board so it's best to get that sucker turning a higher RPM with the full load. My suggestion is to buy another SST Raker prop that is as low as 21 pitch but no more than 22 pitch for those full load boating days. If you switch to another brand and type of prop, you may not achieve what you are seeking because RPM's change so greatly with different types and brands of props.
Well, I understand that rationale, but once again, this is a fish/ski boat. I realize it is more a fish than a ski boat, but it came from the factory with a ski pylon, etc. I also have been around plenty of this style of boat that has pulled a slalom skiier just fine. A friends dad, has a Champion that is about the same year as my Ranger and he has a 150hp Yamaha motor with a 19 pitched prop. I've skiied countless times behind that and never had a problem. He said his only does about 40-45mph, which tells me his is propped way differently. I realize there are difference's in hull's and motors, but I don't see why one would be that much different.

I've been told that 1* in pitch change is about equal to 500rpm's, is that true?

I am also curious why a 3 blade would be better than a 4 blade. I always understood that 4 blade props give a better hole shot. I do understand that changing to a different type of prop could change everything....

Hope that doesn't sound to argumentative, just want to make sure it is clear what I have and what I'm trying to achieve.

Thanks for the input...
 

K.P.

Seaman Apprentice
Joined
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Messages
39
Re: determining which prop to buy

Sorry if I am not thinking of the right boat. A friend of mine had a Ranger 373 in the late 80's that was a bass boat with seating for three and front and rear decks. He did have a ski pylon on his boat but it definitely was NOT a fish and ski. Ranger must have made a significant hull change in later years...sorry.

A 1" change of pitch will result in an approximate 200 RPM change. Going from a 3 blade prop to a 4 blade prop of the same style and pitch will result in approximately 200 RPM less. I don't want to say a 4 blade is what you need but it may help with what you are seeking. Otherwise, a lower pitch 3 blade should be satisfactory as well.

Whether you drive your boat that fast or not, it's critical to prop a boat for the motor to operate in the upper end of it's Max Wide Open Throttle Range if you wish to get the best hole shot, best cruising speed, and best high speed performance. The fact that you want good hole shot and low speed performance when you have a fullload of people, it's important that you prop the motor so it gets close to it's Max RPM rating when you have the full load.

If full load, low speed performance was not critical to you, you could just prop the boat for the peak of the Max WOT range (5500 RPM?) when it's just you and a light load of fuel, and settle for whatever performance you get with 6 people and a full tank of gas.
 

MASTER Brian

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Re: determining which prop to buy

There is no doubt it is more a bass boat than a ski boat, but it is what I've always known a fish and ski to be. I included a picture of what my boat looks like, I can't believe they would have redesigned it much in a few years. According to a Ranger factory brochure on this boat, Ranger makes it out to be a bass boat with an added console to make everyone happy. They stop short of calling it a fish/ski, but I also have the brochure on the 363v and the 365, which they call a fish/play, but I don't see any differences, except seating storage.

Maybe, the bottom is just enough different to make it a bit different, I can't see that, but top side looks just like every fish/ski I've seen from that era. Hmmm...... Is there a difference I don't know about?

I know there are fish/ski and then there are ski/fish. Fish/ski's being more fishing, but setup for skiing as well, with the ski/fish, being ski boats rigged for fishing.

Now you have me curious.....
 

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MASTER Brian

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Re: determining which prop to buy

I did speak to my friend's dad, the one with the similar year Champion and he said having 3 batteries and the 2 12 gallon tanks in the back are killing me as well. But he also said it should do the job.

The local boat shop has a used, in great condition 22* pitched Raker Prop for $350, possibly can get a better price, but they said I can try it out, if I put a deposit on the prop. Is that a good starting point and is that a fair price on a used but good condition Raker prop?
 

Dhadley

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Re: determining which prop to buy

A 17" pitch prop on a good 17' hull should get you way more rpm than what you're seeing. Can we assume you don't have a jackplate and the motor is mounted all the way down?
 

MASTER Brian

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Re: determining which prop to buy

A 17" pitch prop on a good 17' hull should get you way more rpm than what you're seeing. Can we assume you don't have a jackplate and the motor is mounted all the way down?

No jackplate and I want to say the motor is mounted all the way down. I say "want to say", because the bolt is in the middle hole on the top engine mount, but I'm not sure that if it were moved to the bottom hole, that I would be able to place the bottom bolt(s) through bottom slot.

The top mount(s) are 3 individual holes, the bottom mount(s) are long "oval" slots. I looked at it today at lunch, maybe I'll take a measurement tonight and see.

Would it do better if the motor could be moved down? What does moving it up and down do? What would I spend on a manual jackplate? Also, what is the best method of moving the motor? I just read a thread about replacing the silicone in the stern eyes and the motor mount holes every 5 years. I've had the boat 3-4 years and I've never done it, so I am assuming I should do that. The thread said you can do one motor mount at a time and not have to unhook the motor, but if the motor can be moved down and gain performance, then that would be the time to do it.

BTW...the boat is 17'10" minus the motor. Can I ask why you say 17" pitch? I ask, because I currently have a 24" pitch and so far 3 people have said try a 21" or a 22". You've always given me good advice before, I just want to make sure there isn't a mis-communication.
 

MASTER Brian

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Re: determining which prop to buy

Here is what the manual says: (all are 3 blade props)

Boat Size Boat Speed MPH MAT'L. DIA. PITCH
15-19' High Per 50-64 SST II 14 1/4" 23"
15-18' High Per 56-70 SST II 14 1/4" 25"
High Per Bow Lifter 66-78 SSTRX 14 1/4" 27"
High Per Bow Lifter 72-84 SSTRX 14 1/4" 29"
High Per Bow Lifter 40-52 SST Raker 14 1/2" 18"
High Per Bow Lifter 45-57 SST Raker 14 1/2" 20"
High Per Bow Lifter 50-62 SST Raker 14 1/2" 22"
High Per Bow Lifter 55-67 SST Raker 14 1/2" 24"
High Per Bow Lifter 60-72 SST Raker 14 1/2" 26"
High Per Bow Lifter 65-80 SST Raker 14 1/2" 28"
HighPer Tran Lifter 65+ SSTR 14 1/2" 24"
HighPer Tran Lifter 70+ SSTR 14 1/2" 26"
HighPer Tran Lifter 75+ SSTR 14 1/2" 28"

SSTR = Stainless Steel Racer
SST II = Stainless Steel Double Cupped
SST Raker - Polished Stainless Steel Thru Hub
SSTRX - Stainless Steel Over the Hub
 

MASTER Brian

Senior Chief Petty Officer
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Messages
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Re: determining which prop to buy

A 17" pitch prop on a good 17' hull should get you way more rpm than what you're seeing. Can we assume you don't have a jackplate and the motor is mounted all the way down?

Ok, well I guess the motor isn't all the way down. It's actually up a lot. Should it be up or down?
 

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K.P.

Seaman Apprentice
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Messages
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Re: determining which prop to buy

Pictures help a lot. Nice looking rig too! My buddies did not have the starboard side seating area in front of passenger console.

I don't think you need to drop 7" of pitch to get what you are seeking. That'll add 1400 RPM to a motor that is already operating in it's WOT power band.

Is the used prop a rebuilt prop or one that's been sitting around? Make sure it doesn't have any dings in it and ask about a guarantee on the rubber hub...if it has one. Price is a little high but not out of line if it's in good condition.

If the shop will let you try the 22 pitch with a deposit, that's not a bad deal. Just make sure you are familiar with the water you are going in and don't make a day trip out of it. Put the boat in the water, test the prop for a few hours under various conditions if possible, and pull the boat out. Try it under a good load too like pulling a skiier or tube. That'll help in determining if the rubber hub is OK. If you can only try it under light load, make sure you do not over rev the motor.

From the pictures, it looks like you can raise the motor one or two more holes if you wanted to. Each hole raise equates to approximately 100 to 150 RPM increase and is equal to 3/4" raise each hole. The goal is to get the cavitation plate (large flat plate above prop) even with or a little above the bottom V of the hull. Maybe as much as 2" above but I'm not really sure if that is appropriate or your boat. Jack plates are great for achieving the best top speed possible with a bass boat. Even some walleye type rigs. From what you have said, top speed is not what you are seeking.

Try the used Raker and let us know how it goes.
 

MASTER Brian

Senior Chief Petty Officer
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Re: determining which prop to buy

I just checked ebay and found several 22" pitch Raker props for my boat for under $100. I might just bid on one of those. My thinking is even if it isn't just what I want, I could buy the next size down....and still be money ahead.

The props all look nice, am I stupid for trying that route???
 

K.P.

Seaman Apprentice
Joined
May 29, 2008
Messages
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Re: determining which prop to buy

EBay is a buyer beware type thing to me but you may end up finding what you need and save some cash. I highly doubt you'll be trying a wide range of props. Your already there with what you have. Your just looking for more hole shot with full loads. That's usually a two pitch change.

Certainly some good deals on there though. Good luck.
 

Dhadley

Supreme Mariner
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Feb 4, 2001
Messages
16,978
Re: determining which prop to buy

Don't know why I thought you had a 17" prop, my bad. A 24 Raker is a pretty good prop. They like a lot of height and your motor being in the 3rd hole may not be high enough for it to perform it's best. Especially if it's still in good shape. If you can use 90% of your trim range without it venting it probably can stand to go higher.

A lot depends on your hull design. Most boats with a pad & a step like a lot of X dimension (motor height). Some boats with that design actually measure 23-25" at the transom but are intended to use a 20" motor. Even if you could get to 5200 with an average load that's still pretty hard on the motor (lugging). We rarely, if ever, drop pitch to simply gain rpm. That usually decreases efficiency. I'd rather raise the motor to lose drag which gains rpm and increases efficiency.

As for the Rakers you'll find, just try to find one that has not been rebuilt. Even today many prop shops don't have Raker pitch blocks and they simply use SST pitch blocks. Basically you'll end up with a shiny SST. Once you run it you'll know right away. If it doesn't have a lot of lift then it's not a true Raker.

The RX props are an awesome piece but rarely work for skiing since they're an over hub prop. In most cases they need to be sent to a prop specialist to have them "dialed in".

Another good prop for that boat would be a Turbo Lightning. They have more lift than a Raker and work real well on most Rangers. After 21" they come in every 1" increment. I'd say a 23 Lightning might work real well on that boat.
 
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