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ContinuousWave: Whaler Performance
Re-Pitch Rapture Prop
|Author||Topic: Re-Pitch Rapture Prop|
posted 08-25-2004 04:16 PM ET (US)
Executive summary: Where do I send a Michigan Wheel Rapture 14.25x15 prop to have it dropped in pitch, so as to gain ~500 rpms?
Main body of story: We have a tough (3/16" thick hull), all-welded 20' aluminum hardtop boat for fishing/shrimping/crabbing up here in NW Washington. The boat is fairly light, but the boat manufacturer is constrained by his equipment to building a hull which is pretty heavy up front, and tending to be slow for its size and weight. At moderate (cruising) speed, the hull is pretty efficient, but at speeds faster than 30 mph it really flattens out and drags, no matter how you trim. The boat probably weighed ~2800# in my test condition - and I got 41 mph at 5400 rpm trimmed out. With a prop slip of 6%, that calculates to a 16" pitch prop - greater than the 15" advertised. With a heavier, more normal load, I get ~ 38 mph / 5200 rpms.
The motor is a 2001 175 Ficht Evinrude, and I need rpms to be ~5700 - 5800 at WOT if we want the motor to live. Due to the light weight, trim tabs, and flattish front to back hull profile with a minimum deadrise of about 18 degrees, it's not too tough to plane - I can keep it on plane down to ~14 mph when the going gets sloppy. I don't need to be told that 175 hp is not adequate - if it will hold plane at that low speed and cruise normally at 26-30 mph (at 3800 - 4300 rpm), it has adequate power. With the wind chop we normally have through the Georgia Strait, I don't need more speed.
So that's my dissertation on why I'm not underpowered and don't need to drop 10k for a new 225. Where should I send the prop?
posted 08-26-2004 11:34 AM ET (US)
Being this is not Whaler related I doubt ANYONE here would tell you to buy a new engine or that your rig is too slow. they will however tell you to buy a Whaler. Don't know what kind of sites you visit but we are not a bunch of assholes here.
One of the best prop shops in the world.
posted 08-26-2004 03:34 PM ET (US)
Amen on the General Propeller comment.
Bob on Tampa Bay
posted 08-26-2004 04:13 PM ET (US)
Obviously I struck a nerve. I lurk here much more than I post, and have bought items from several members here, including an OMC binnacle control from you, Bigshot. That transaction was super easy and went well, and the product I received was better than described.
Sorry if I come across as defensive, but given the way some folks rant about underpowering and the lack of availability of performance propellers in the lower pitch ranges, I felt my question and explanation was valid. Thanks for the link - I'll give them a call.
posted 08-26-2004 06:18 PM ET (US)
Vek, You sound legit so lets give it a shot.
It's not advisable to remove that much pitch [ 4" ] from a s/s, prop because all they can do is bend the very tips of the prop, but the pitch starts at the hub & there's just no way they can bend the thicker hub portion of the prop so you don't get a good prop back.
My suggestion is to buy a s/s Stiletto in the size you need for $249.000 no tx delivered to your house.
If you need the number e-mail me & I post where to get it.
posted 08-27-2004 01:07 PM ET (US)
No nerve struck, just thought you were having some problems at other sites and hence why you just wanted the info you seeked. I agree with Sal, and I think GP will ONLY do 2" either up or down in pitch. 2" shuld give you about 400 rpms though but a repitch with shipping both ways might be about $150 so......
posted 08-28-2004 02:37 AM ET (US)
Based on Sal and Bigshot's comments, its almost a no-brainer: buy the new prop...another plus is you'd have a spare that you know mostly works.
You might check with sort-of local-to-you prop shops (Prop Shop in Mukilteo, Seattle Propeller in Kent) to see if they have any kind of trial program to help you get the right pitch prop. I've never done business with either of them, but did talk with someone at Seattle Propeller a year ago--he gave a no-holds-barred commentary on my old prop (basically confirming my opinion, and that of another respected member of this forum). Notice I said "old" prop...now I have a Mercury Mirage Plus, and am very happy with it (I got lucky--bought it off eBay for the price of a new Stilletto)
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