PROP SIZE

NOAHSARK · #1 03-09-2006, 05:00 PM

You guys know that I have been dealing with this prop swap since I p/u the 23'last week. I just had a 14x17 put on and was wondering what kind of performance should I expect. Here are the exact details on what I am running, if there is anyone running the same, please chip in a give me some #'s. Thanks again

1989 23'CC SC
225 Yamy SaltwaterSeriesII 0X66

Bigshrimpin · #2 03-10-2006, 12:29 PM

NOAH - you can figure out the cruising speed by using a prop calc . . . just plug in the numbers for a 17pitch prop @4000rpm and assume a prop slip of about 12 - 15% for an depends on load, wind, and waves (if you have a top then .15 - .18 - maybe more) The gear ratio of your 225 (1.81). I've found these calcs to be very accurate using many different props. The only thing you won't know until you test out the prop is the WOT rpm's . . . just make sure that you prop the boat on the upper end of recommend RPM range (5500'ish)

http://www.rbbi.com/folders/prop/propcalc.htm

gss036 · #3 03-10-2006, 05:15 PM

I am running a 14 1/2 X 17 Merc stainless on my 89 Merc 200 w/Seacraft 23WA. I get about 4300-4400 rpm depending on water. The prop has some cup in it and really holds great on turns. I would think w/225hp that you would be about 4500-4600 w/o any problems.

Bigshrimpin · #4 03-10-2006, 05:29 PM

Gary - if you WOT is only 4400 . . . you're overloading the motor. Drop down to at least a 15P or a even 13P.

NOAHSARK · #5 03-10-2006, 05:58 PM

thanks for the input fellas, big shrimpin thanks for the calc link its a great tool. I had a 21p on there and topped off WOT @ 4700rpm, now that I dropped to a 17p I should pick up another 600rpm putting me right where I need to be, close to 5500rpms. Im curious to see what my hole shot is going to be like though.

NOAHSARK · #6 03-10-2006, 06:00 PM

old salt whats your diameter on that 17

Blue_Heron · #7 03-13-2006, 09:02 PM

I've been playing around with prop options for my 20' SF and found this:

http://www.mercurymarine.com/everyth...ut_propellers6

It's a tutorial on props. There are lots of variables to consider. Most folks talk about pitch, but diameter, number of blades, cup, rake, and blade area all affect efficiency and how a prop will handle. It's worth checking out if you want to learn more about props.

I started out with a 19p that ventilated bad at high engine trim and in turns with a WOT RPM of 5300 and 41 MPH and ended up with a 22P with WOT RPM at 5500 and 49mph. The difference was slightly less blade area, more cup, and more rake. I was also able to raise the engine one hole once I was running the right prop.

FELLOW-SHIP · #8 03-10-2006, 05:54 PM

I have a 1976 23 CC with a 225 Yamaha OX66 with a 30’ shaft on the transom. I am running the 3 bladed 17 prop and it is the perfect prop for the boat. Cruses well at 3500 to 3800 rpms at 25 to 28 mph tops out at 52-5300 I really don’t run it that hard so I can’t remember the mph at that speed but it seems to me my gps says 10 mph less that my rpms at most all planning speeds. I have a 18” for my back up.

FellowShip

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