Inboard prop size

classictrade2 · #1 08-24-2006, 12:02 PM

I have been doing a search on proper prop size for the 23' inboard and was wondering what prop Miles offshore ended up with or any other suggestions. Is the correct prop a 16 x 17 with a # 5 cup? I bought my boat with the 4 blade and it is a dog. 17 knots burning 12 gph. There is no cup but after reading the post, I guess I need to trash the 4 blade and get a 3 blade. I have an old 17 x 17 3 blade I have as a spare. Can I use the 17 x 17 with say a #3 cup to get the same results as the 16 x 17 # 5 cup? I AM SO CONFUSED!!!

Classic Trade

classictrade2 · #2 08-24-2006, 12:32 PM

I forgot to say that I have the 351 ford engine in the boat and I believe it is aroung 250 hp. Thanks for the help.

Classic Trade

Miles Offshore · #3 08-24-2006, 10:15 PM

Hey Author???- I am now turning a 16/15 old ragged spare wheel- the 4 blade was a dog for sure and i would be happy to sell it to any interested party

I am going to by a 16-17 soon and that is what i plan on running- no cup- your wheel sounds fine (the 3 blade) make sure your rpms max out in the 42-4800 range and you should be fine- With lite fuel and the 3 blade i am burning 9 gph and getting 20 to 23 knots depending on tide/fuel etc with 2 people. hope this helps-

classictrade2 · #4 08-25-2006, 02:16 PM

Thanks for the reply. I am planning on posting pictures of my 23 but I am so computer stupid, I am not quite sure how to do it. So I need no cup with the 17x17? I thought a cup was good for the seacraft inboard. I know it is needed in football.

Arthur

riprunner · #5 08-25-2006, 03:02 PM

Miles offshore,

I'm getting around the same speed numbers as you, but I'm burning just a touch more at 10-10.5 GPH. what RPM are you getting that cruise at. I'm at around 3400 and swinging a 15x17 prop. This is also with a new EFI 350 rated at 350hp. I was hoping for a better cruise with that power. Any suggestions?

Miles Offshore · #6 08-25-2006, 09:05 PM

R/R- you should be doing a heck of a lot better than that I think- you have quite a bit more horses than i do- how many rpms is it turning wide open??? I think you might be under propped a little- i think all that extra hp acounts for the little bit extra fuel consumption (maybe) . I normally run between 3K and 3200.

hey Auther- been waiting a while to see pix of your ride!!!!

craig

classictrade2 · #7 08-28-2006, 09:07 AM

I changed out my prop over the weekend to the 17 x 17 3 blade and what a difference. I am now running at a solid 20 knots at 3000 rpms. I think I may need to drop to a 16 pitch because my top rpm on the motor I could achieve was only 3900. I also had a noise and vibration that I have found to be the cutlass bearing. This should be fixed this weekend and then I will see what my top end rpms are and decide about the prop pitch. Thanks a lot Craig for helping me through this.

Arthur

Gary Hill · #8 08-29-2006, 08:26 AM

I have a 350, 315 HP and have a 17 x 16 with a little cup and turn around 4600. At 3000 I'm running 23-24 and burning around 9.5-9.8 gal's per hour. At 3200 I'm running 26-27 and burn 10.5 gal per hour. You need to have it proped so you can turn 46-4800 rpm with a good load in it (full tanks-three people) or the engine is lugging which is not good for it.

riprunner · #9 08-29-2006, 09:06 AM

Knot Working, Those are great numbers and where I love for this boat to be. If you are turning those numbers at cruise, what type of top end are you getting? How much room in the tunnel do you have with that prop, I think you need a minumum of 2" to be safe?

I think I'm going to play with some props soon.

Gary Hill · #10 08-29-2006, 04:30 PM

I don't know the exact measurement, but there is plenty of room ( I will measure) at real low RPM 1500-1700 I have a little rumble from prop tuberlance, but it is only in a real small range, and I had a little when I had the 351, 233HP. I turn at 4600 RPM 37 MPH. With the 4-barrel wide open around 17 GPH.