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Posts: 443
Location: Indiana | I have a 2008 ranger 620 with an Evinrude 225HO. I currently run a 4 blade 14X21 stainless prop. The motor is mounted as high on the transom as it will go. I have decent hole shot and top end speed. But rpms run a little low (I forget the actual number but will get the boat out in the next day or two and report back).
I am going to buy a second prop, mainly as a spare but also for use in shallow rocky water. I think I would like aluminum as it will be used in these shallow rocky waters where I don't want to take a chance of tearing up my stainless prop.
I know that I could turn more rpms compared to what the motor can run. Top end speed is not a big concern of mine. Hole shot would be my main concern as I pull skiers and tubers in the summer pretty often. But for the skiing my current prop does pretty good.
I guess I am interested in what effect pitch change typically has, if lowered or raised, on rpm and speed. Same with 3 vs. 4 blade design. Also what can I expect as a change in going from stainless to aluminum? |
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Posts: 1887
Location: syracuse indiana | try a 21 p tempest plus . that prop will do wonders for you. i run a tp 19p on mine and thats the best prop for heavier boats...bill |
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Posts: 443
Location: Indiana | I ran a tempest on my last boat. It is a good prop. I am looking for a spare so I don't really want to spend the money for a second stainless prop when my current one does a good job. |
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Posts: 81
Location: Indiana | From VMS regarding my prop/boat question. "I would suggest staying at the same pitch, but see about trying a highly raked, highly cupped 3 blade prop...like the michigan ballistic. The blades are heavily cupped and the prop fins are thinner, so it will bite the water really well" So that could be a three blade option. He also said if we switched props that yours would bog mine down more so if your looking for more RPM's you should drop down but I'm not sure about aluminum flex if that causes an issue. Hopefully VMS can chime in. |
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Posts: 3508
Location: Elk River, Minnesota | Hiya,
I'm here for a few days...so if you get the RPM numbers, I'll chime in. No doubt going to an aluminum alone will reduce performance. What may likely happen is you will see more slip with the prop and with the motor mounted as high as it can go may mean very little ability to trim the motor up on plane without blowing out. One suggestion there that might (tongue in cheek firmly placed here) is a solas propeller which will act more like a steel prop at the price of an aluminum.
Depending on your RPM numbers, if they are not all that low and you do want the aluminum, you might be able to get away with a 4 blade solas if they make it. Just going aluminum will gain you some RPM's due to the weight of the prop and a little more flex than steel.
Another option if you would like to potentially stay stainless... Ebay. I have purchased many used props from there and all have been good props. I have yet to receive a prop that was not in good shape.
If a 4 blade is what you would like to stay in, and aluminum is not an option, that tempest prop would be a good bet. possibly dropping 2 inches in pitch (equivalent to roughly 400 rpms gained going down) would definitely help the hole shot, but top speed will be reduced a couple of MPH as well. Decent trade off if you pull tubes and skiers though...
I'll be around a few days here...
Steve |
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Posts: 443
Location: Indiana | Thanks Steve,
As soon as I get an evening without thunderstorms I will hit the lake up the street and get my rpm numbers. I appreciate your knowledge and willingness to help.
I may not have been clear. What I mainly want is a spare prop that will get me to shore in case of an emergency, and to use on our trip to Canada every few years to protect my expensive stainless one. So I was hoping to keep cost down some and thought aluminum may fit the bill. I have heard in the past that aluminum may also protect a lower unit more than stainless from a hit on a reef, so that was my main reasoning for aluminum. I am certainly not married to that idea.
I had read that if cupping/rake/diameter remain the same one might expect the 200 rpm increase with a 1" drop in pitch. I also heard that an aluminum prop , due to slipping, will reduce rpm's somewhere around 200 as compared to a similar stainless. So I was trying to figure the pitch I might try as a starting point.
So many variables for a non professional such as myself to consider. Honestly the performance is good, I just thought if I could get a spare prop AND play around with increasing rpms it might be cool. If that cant be done, maintaining rpms will work.
You are right on the holeshot. And I am one of those oddballs that could really care less about top end speed (within reason). I would trade for better holeshot than top speed almost any day of the week. |
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Posts: 3508
Location: Elk River, Minnesota | Hiya,
Did a little search of solas propellers and found this...
http://solas.boat-props.com/Evinrude/225_HP_%282005Newer%29_21.00-P...
I think for the price, this will be pretty hard to beat..
Steve |
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Posts: 443
Location: Indiana | Cool, looks like a good find.
I took out the boat tonight. I get maximum of 5100 rpm trimmed up as much as possible before catching any air or blowing a huge rooster tail. I believe the engine calls for 4500-5800, so I am in the range for full throttle rpms.
Should i even mess with trying to increase rpms?
Any guess on what I can expect with that solas? Mainly curious as to the difference in aluminium to steel. It is same diameter and pitch as my current prop, but cupping and rake may be different too.
You mentioned above 'tongue in cheek' while referring to solas. I am not against spending more for quality, if there are questions. email me if you prefer.
[email protected]
Thanks again! |
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Posts: 3508
Location: Elk River, Minnesota | Hi again,
if you are getting 5100 with your original prop, in my humble opinion you are over-propped by about 3 inches or so in pitch. If your motor calls for up to 5800, it is best to be very close to that value to let the motor really be able to turn well in all conditions. I am assuming that when you ran the motor you were loaded as you normally are for most situations....
As for the tongue in Cheek, that was for the prop not blowing out at the highest motor setting on the boat. Solas makes a great prop. I had one on my old boat and I carry one as a spare on my current boat. Ran it a few months ago and it performed just as solid as my ballistic steel prop, with the same pitch.
The solas prop is fully cupped along the trailing edge, and is made using a process called squeeze casting, which flexes less than a normal cast aluminum prop. I would definitely say it is worthwhile for a spare. I would say with your spare, drop down to a 19 pitch and that should put you right around 5800 with your spare prop. There will be a loss of speed, but your hole-shot will be dynamite.
I would also recommend at some point trying an 19 pitch 4 blade steel prop as well....it will get you roughly to 5600 rpms or so, with the potential of being more since there is a limiting factor to the motor in how much it can turn. When you reach the limit of the motor with the prop, the RPM's drop dramatically.
Steve
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Posts: 443
Location: Indiana | Yes, I was loaded as normal, and even tried heavier and lighter loads by adding people, gear, and water to the livewell. 5100 was the absolute highest reading.
I will buy the solas and give it a go as a spare. I will also look for a 19P 4 blade stainless for comparison sakes. Thanks for all the info.
Mike |
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Posts: 443
Location: Indiana | Was getting ready to order the above mentioned solas and noticed a rubber hubbed version the rubex. Do you have any experience with those. For the $15 dollar or so difference it seemed like a decent idea.
Mike |
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Posts: 3508
Location: Elk River, Minnesota | Either one would work well. the rubber hub version is the exact same design, it just doesn't have the multi-engine use...it is strictly for your motor.
I believe one of the two has free shipping too yes?
Steve |
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Posts: 443
Location: Indiana | I know the rubex does, and believe the amita does as well.
Thank you again. It is on order. |
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Posts: 443
Location: Indiana | Got the new prop and it looks great, went to swap it out and have one last (hopefully) question.
Does the thrust washer from behind the original prop come off to be replaced by the one that came with the new prop?
I tried to gingerly remove it, but it would not go. If doesn't come off, I don't think the new prop will work (see pics below of thickness of the two washers and the gap between the new prop and lower unit if using the original thrust washer). Maybe I need to soak with PB Blaster or WD40 and try again. Advise please.
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Posts: 443
Location: Indiana | Got it. Just took a little bit of elbow grease. I wonder if they used grease when they put the original on. Note to self...Put grease on shaft as the book recommends.
I an really not this mechanically challenged, I am just playing it safe. |
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Posts: 3508
Location: Elk River, Minnesota | Yep...If it was stuck you can also lightly tap it with a hammer on the side while you use a lever of some sort (like a screwdriver) on the underside pushing up on the washer.
Hope the new prop works well....I'm curious to see how it performs for you.
Steve |
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Posts: 443
Location: Indiana | Results are in the 19" pitch 4 blade aluminum gave me about 500 more rpms, reduced max speed by only 1.5 mph and improved holeshot by about 14%, over my 4 blade 21" pitch stainless. I am very happy with it. I am afraid this may become my main prop and my $650 stainless the spare. How backwards is that.
This could get addicting. I wonder what a 19" pitch 4 blade stainless would do....... |
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Posts: 3508
Location: Elk River, Minnesota | Throw you back in your seat for hole-shot 
I'd bet a 19 pitch 3 blade would be excellent!!
Steve |
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Posts: 443
Location: Indiana | So does a 3 blade typically have better hole shot? Is that due to weight, bigger blades or what?
If you have a moment, what else is the difference between 3 and 4 blades? How about stainless to aluminum? Obviously there is less flex and weight with aluminum so stainless should give you better bite, but fewer rpms, right?
I may be overthinking all of this, but it is interesting how big of a difference this can make. Thinking through my last boat, I was probably over propped in it too. Would have been cool to test out. |
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Posts: 3508
Location: Elk River, Minnesota | Hiya,
The 3 blade is a good all around style for both speed and decent handling. Due to one less blade, the motor can turn the prop easier, thus allowing for a higher pitch prop, with a less hole shot. What manufacturers do to offset a slower hole shot is drill the vent holes in the hub of the prop to allow some exhaust gasses onto the blade of the prop, causing it to slip, creating higher RPMs, which at a certain point in the RPM range, the exhaust bypasses the ventholes, the prop grabs the water and shoots you up and out at a higher rpm.
A 4 blade is usually for heavier boats, hole shot and handling. Due to the extra surface area of the 4th blade, a lower pitch is needed to turn, which as a result gives excellent stern lift and an awesome hole shot.
With your motor, I would think a 3 blade aluminum would not be worth your time due to the flex and the lack of cup on the trailing edge. In a 3 blade steel, one with high rake and cup will give excellent bite for handling (especially at high motor settings) and top speeds. so...your assessment of steel vs aluminum is spot on.
I wonder if you could find a 3 blade tempest to try...
Steve |
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Posts: 443
Location: Indiana | Didn't find a tempest but did get a Viper 3 blade 19 pitch. Ended up at 57.8 mph, 5700 rpm and a hole shot like no other. Got this prop used from a guy who carried as a spare. It was a steal, and may become my primary prop except for when doing a lot of cruising. |
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Posts: 3508
Location: Elk River, Minnesota | Very cool!!
can you raise the motor another hole? Might gain that extra 100 RPM and get you that much closer to 60...
Very cool...very very cool...
Steve |
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Posts: 443
Location: Indiana | It is mounted as high as it will go. To try toget 60 with this prop my only hope is to lighten the load (less fuel, gear and by myself). It was also a little choppy with a light wind so there are improvemnts there as well. But 100RPM and 2.2mph, I don't know about that. |
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Posts: 81
Location: Van Buren, Indiana | Hi Mike! If you want to if you want to experiment some and continue the fun! I would suggest looking at a 6" Hydrodynamics Rapid Jack it will let you make alot of changes and set ups for diferent water conditions. Had one on my '04 Lowe Stinger w/ 150 Johnson 2-stroke it was amazing they used to run around $260 check them out at hydrodynamics-usa.com!
Edited by Ifishtolive 8/16/2011 8:38 PM
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