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Author Topic:   Propeller Test Data
PSW posted 12-01-2002 06:45 PM ET (US)   Profile for PSW   Send Email to PSW  
Today I tested 4 props on the 1991 Montauk with 1991 115-HP Mercury. The conditions on the lake were calm with mid 50's air temp and clear sky. I had good info from both lhg and Bigshot on what prop they thought was best. They recommended the 20-inch pitch Laser II.

The prop shop set me up with 3 props and I had my aluminum that came with the boat. The 20 Laser was on order so I had to test without it. Here is the breakdown.
PROP PITCH 3000 4000 RPM WOT
ALUM 21 22.7 34.5 5250 48.4
RAPTURE 19 22.1 33.1 5500 46.6
LASER 22 22.9 35.7 5200 48.1
TURBO 4 21 27.5 36.9 4600 43.7

DATA IN MPH

As you can see the Laser II is probably the ticket or maybe a 21 Rapture. Stock Aluminum was suprisingly the quickest while Rapture was most responsive. Great cruise with the 4 blade Turbo. The laser had by far the most slippage. most likely from being too much pitch while the others were questionably low in slippage (1.57-2.91)? Is it possible to have this low of slippage with brand new props and based on this data does the 20 Laser still look to be the best option. I would like to see the differing opinions and thoughts of the prop shop owner, myself, and the forum.

Hope to hear some input.

Also my cavitation plate is set 1/4 to 1/2 inch above bottom of hull. Any thoughts or impact that may have I would like to hear.

Thanks,

PSW

PSW posted 12-01-2002 06:46 PM ET (US)     Profile for PSW  Send Email to PSW     
Sorry data from excel must have gotten taken out of spreadsheet form
Bigshot posted 12-02-2002 09:21 AM ET (US)     Profile for Bigshot  Send Email to Bigshot     
Save your money and run the aluminum. So far I can't find a SS prop that beats my alum on my 70. Weird but it happens.
weekendwarrior posted 12-04-2002 10:35 AM ET (US)     Profile for weekendwarrior  Send Email to weekendwarrior     
There is a lot of neat prop test data on the Honda-Marine web site:

http://www.honda-marine.com/prop_test/

I saw a few whalers listed in there. Unfortunately the format doesn't seem to be standard and some boats have better data than others. Overall it's interesting data.

weekendwarrior posted 12-04-2002 10:40 AM ET (US)     Profile for weekendwarrior  Send Email to weekendwarrior     
I forgot to mention, some boats are tested with only one prop and others are tested with multiple props. Suprisingly some are tested with non-Honda engines.

The data seems accurate, my old boat/motor/prop combo is listed and it matches exactly what I was seeing as far as speeds vs. rpm (I didn't test the time to plane, etc..).

Barry posted 12-04-2002 11:00 AM ET (US)     Profile for Barry  Send Email to Barry     
What I found most interesting was the Honda data on the 18' Guardian running the 130 with the Hydro-Foil installed.
John W posted 12-05-2002 12:00 PM ET (US)     Profile for John W  Send Email to John W     
Obviously the Turbo 4 blade gave the best cruise but at 4600 rpm top end it's overpropped...a lower 4 blade pitch would give you the proper rpm's but those cruise numbers wouldn't look as good then. I agree the laser II might be the answer, that's what my father ended up with on his 90 Merc/16'7" whaler. But for giggles you might try the 4 blade again with the motor up one or two bolt holes, it should run with the cav. plate at least 1" above the bottom, and can probably hold on mounted higher than that. Mounted higher, your speeds & rpms should both increase.

As Bigshot said, the aluminum prop is giving you decent performance, so spending more $$ for an SS prop may not be worth it. But I hate aluminum props as I end up brushing sandbars, etc, and they're immediately ruined. SS props are so much more durable that they're worth it for me even without performance benefits.

jimh posted 12-05-2002 11:33 PM ET (US)     Profile for jimh  Send Email to jimh     
The text entry field only allows entry of text, so if you pasted in a Spreadsheet, it gets converted to text.

To make tabular data readable is difficult since the font is likely to be a proportional spaced font, jumbling everything.

I suggest you re-post your data using this format, which works well in these cases:

21-Aluminum Prop
-------------------
3000 RPM = 22.7 MPH
4000 RPM = 34.5 MPH
5250 RPM = 48.4 MPH (WOT)

jimh posted 12-05-2002 11:38 PM ET (US)     Profile for jimh  Send Email to jimh     
If the slip percentage is always too low to be believable, perhaps you have the wrong lower unit gear ratio factor in the equation.
PSW posted 12-06-2002 11:52 AM ET (US)     Profile for PSW  Send Email to PSW     
That is what I thought too, but the owners manual states that it is a 2.07 ratio. I am going to return the last prop I tested yesterday which was a 3 blade turbo 21. Only got 5000 rpm with 2 people and 46.6 mph. I have decided to go with the 21 rapture since it performed the best. The 22 laser pulled 5200 so the 20 would be out of my rpm range. Currently I am running at 1/4 to 1/2 inch above with the cavitation plate. If I go 1 hole up I would assume that would put me at around 1 - 1 1/2 above, which many on the site claim is optimal. Now how much is that going to change my WOT rpm? I am already getting 5300 + from it.

PSW

PSW posted 12-06-2002 11:56 AM ET (US)     Profile for PSW  Send Email to PSW     
Jim could you paste this topic in with my 115 test run topic. I somehow have both going at the same time all of a sudden and they are about the same thing.

Thanks,

PSW

Marv posted 12-06-2002 04:24 PM ET (US)     Profile for Marv  Send Email to Marv     

I am curious about your test results--note the pitch but what about the diameter.

Doesn't that make a difference in your RPM too??
Example--12 3/4 x 21 may be equal to a 13 1/4 x 19 or 20. Watcha think??

Anything written on diameter around??

Reason I am asking is I am trying to prop a Honda 90 and don't have any way to get test props from Boat US. (They would charge a restocking fee if I returned one.)

I am reading all I can from all the great responses here --trying to find the best all round prop. Your tests are an excellent help to compare. Thanks

Sal DiMercurio posted 12-06-2002 06:13 PM ET (US)     Profile for Sal DiMercurio  Send Email to Sal DiMercurio     
Psw, you don't say what the recommended maximum rpm is for that particular engine.
It's best to prop the engine so it is able to reach it's recommended maximum rpms with a normal load & trimmed out.
Again, I stress, there is absolutly "NO" need for a 4 blade prop in your situation.
If the Michigan Raptor gave you the best performance, i'd go to a Stiletto of the same size, as they are darn near identical.
You can get a s/s Stiletto for $249.00, no tax from aftermarket.com
Marv. the difference from 12-3/4 to 13-1/4 is so minute, [ 1/2" spread out over the 3 blades ] will not change the rpms more then 25 rpms, if that.
Without knowing the recommended maximum rpms for that engine, plus the size of [prop your running now, theres no way we can figure whats right for your engine.
Whatever you do, don't over prop the engine, which means your rpms can't reach what they are supposed to.
Sal
Sal
Barry posted 12-07-2002 09:46 AM ET (US)     Profile for Barry  Send Email to Barry     
Sal, it appears from the aftermarket.com site that they just sell car parts?

http://www.surplusunlimited.com/ sells Stiletto props for $259.95-$269.95 and Michigan Rapture props for $269.95-$279.95.

I would recommend that PSW purchase from the prop shop he is using. Sounds like they already loaned him 4 or 5 props so he owes them.

Marv posted 12-07-2002 10:21 AM ET (US)     Profile for Marv  Send Email to Marv     

RE----prop purchase---Props are like underware----- so stay with the guy who helped you as it is very difficult to get any dealer to cooperate even if you guarantee purchase.

RE----diameter of prop sure made a difference in racing modelplane engines---I would think the fluid dynamics at slow speed would show more difference. Wish I could set up a test and try out several props one boat--same weight etc..

Weekend is right--Honda lists a series of tests with diff props on same boat--only slight weight differences--interesting to chart but no conclusive cigar.

After reading alot on this site, I am leaning toward a 13 1/4 x 19 for my purchase for Honda 90 on a Newport. I will post results.

Marv posted 12-07-2002 10:24 AM ET (US)     Profile for Marv  Send Email to Marv     

Yeah--Sal is right re RPM---I am told to stay near 6000 by a mech--so the reason for 19 pitch.

PSW posted 12-07-2002 06:51 PM ET (US)     Profile for PSW  Send Email to PSW     
Picked up the Rapture on Friday from the prop shop it is a 13 1/4 X 21. This is a great prop. If I would not have had the luxury of testing so many other props this is probably the prop I would have went with off the bat. Tell you what though it is nice to see the differences. Max rpm is 5250 and bare boat with 2 people I can pull all that plus some. Although I was careful to make sure not to buy a prop that would allow me to pull too much because I was informed that this particular Merc engine is not good to run in the high 5000 rpm range like many new motors. Something about the sleeves. And I like to always get atleast the max under normal load, so I had to be careful. Price was $325 for brand new in the box. Could have gotten less for like new test, but I wanted in the box. Well worth it if you think about how many props I test brand new. The shop also said I could exchange my 21 for a 19 to use skiing for just a few bucks. How awesome. Anybody in the state of WA should head to this place in Mukilteo. Thanks for all the input and I am glad to be done testing props.

PSW

Dick posted 12-07-2002 07:54 PM ET (US)     Profile for Dick  Send Email to Dick     
PSW

I have been in the marine business here in Seattle for 16 years and have tried many of the prop shops. The Prop Shop in Mukilteo is by far the best.
Nice to find someone that will work with a customer as they did for you.

jimh posted 12-08-2002 10:36 AM ET (US)     Profile for jimh  Send Email to jimh     
Re: Maximum RPM for 4-cylinder Mercury 115 = 5250

I have heard this cited elsewhere, with the warning not to exceed that crankcase speed. Apparently this particular engine does not like to turn at higher speeds.

Bigshot posted 12-09-2002 09:43 AM ET (US)     Profile for Bigshot  Send Email to Bigshot     
Redline is redline kids....don't exceed it. It is better to pull 5k WOT than 5300. Getting to max rpm is not crucial. If engine redlines at 6k and you only get 5600, that is fine if the performance is what you desire. On this engine I am getting better performance at 5500WOT(52-5800redline) than I do with a prop that yields me 5800 on the nose.
Sal DiMercurio posted 12-09-2002 07:43 PM ET (US)     Profile for Sal DiMercurio  Send Email to Sal DiMercurio     
Remmber this while testing for wot rpms.
You load you boat like you normally would when going fishing, or boating or sking, or whatever, not a light load.
Run her at wot & trim her out.
You don't want the rpms to be at the low end with no load on the boat, cause when you do put a decent load on her, she will be waaaay down on the rpm range.
Thats why it's important to allow the engine to be able to reach very near it's max rpms.
Nothing kills an engine faster, then lugging her down below the recommended rpm range while at wot.
It's much better to be able to reach it's max rpms, then to be at the bottom of that range.
The engine isn't capable of producing it's 150 or 200 or whatever hp it is, until it reaches very near it's max rpm range.
A couple hundred roms below wont hurt anything, even a couple hundred above, as long as you back off & don't exceed the max.
My 2000,.......200 hp FICHT [ on my 20' deep V outrage ]is rated at 5,800 rpms, & when I run her on the ocean [ can't ever run her at wot ], I run a 14.25 x 19 Stiletto, because she hangs on better then the 21 pitch, but will darn near kick in the over-rev shut down safety device at 6,200 rpms.
Keep in mind, I am not able to run her at that rpm on the ocean, as the sea conditions just wont allow it.
Now, when I'm fishing the river [ Sacramento ], i'm able to run the 21 pitch & she maxes out at 5,800 rpms while up on the 3rd set of holes, giving me a hair under 61 mph, while the 19 pitch turns at 6,100 rpm [ 62 if I let her run & trim her up in 1 ft chop ]& just under 60 mph.
So you have to play with it until you find which is best for your type of conditions.
Sal
PSW posted 12-09-2002 11:06 PM ET (US)     Profile for PSW  Send Email to PSW     
Sal you are right on the money. That is why I tested so many props and wanted to find one that would get all the 5250 maybe even 5300 when trimmed right because I knew this was as light as the boat would normally ever be. I found that prop and now have the ability to get the performance I want under different loads. I did not want to be the guy that puts 5 people in the boat at the beach house and goes for a ride and when someone says it hit I watch my tach climb to 4600 rpm. I even am going to keep a 19 aluminum for skiing. Thanks for all the input everyone and I hope this post has helped those needing a prop that have not had the luxury of testing so many different combinations.

PSW

Bigshot posted 12-10-2002 02:47 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
Ok...with 2 strokes I find that getting close to max rpm is the best with a light load, weight dramatically reduces the rpms. With a 4 stroke it is not as crucial being the weight does not drop rpm's as much as a 2s due to torque at that rpm range. I think when we discuss props and propping a boat it is important that we are on the same page with the same engine, etc. Comparing a 2s to a 4s is very different believe it or not.

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