23 Inboard numbers with new 16x17 wheel

[riprunner]

Finally after months of research and talking with people from this board as well as others I finally bought a prop for my 23 inboard. I was running a 15x17 LH wheel pushed by a new MPI 350 and was only getting about 18 knots on test day at 3000 RPM and just under 10GPH. I went out and bought a brand new 16x17LH prop that is also the factory spec. Because I have waited so long to see what this boat should perform at I took a couple hours off work and headed to the boat. I went out with my dad, both of us over 240 pounds & full fuel and ran the boat with the above posted number, I’m not sure how hard the tide was running, so that’s one small factor. The marina next door has a travel lift so had them pull the boat and I switched the prop. The first thing I noticed about the new prop was it was much beefier than the prior prop and again I couldn’t wait to hit the ocean and see what she would do. So I get to the break water and push the throttle down. To my absolute amazement I get the same exact $%#%# numbers as the other wheel. Same speed, same GPH, and going the same direction on the same day on the same tide. The only difference is now I get more vibration.

What’s the deal I here….? I expected to get better numbers, or at least worst numbers, but everything was exactly the same even the hole shot. I couldn’t be more disappointed and at close to $500.00 later. I only had a few minutes to test it because I had to get back to my office, but everything was identical according to my GPS & smartcraft gauges. I have charters both Saturday & Sunday so I’ll see if there’s any difference when I add more weight to the boat. I think I need to go for a ride in another 23 inboard to see what the differences are. I have a big tall T-Top, but I just can’t see that slowing me down that much?

[oldfielder]

I haven't followed your research, but I'm wondering if pitch would have had a more dramatic impact in the direction you were trying to go. I think you need a certain diameter to push water, but the proper pitch is what is really going to dictate your forward motion.
Did you center your research around WOT with the old prop? It will be interesting to see if you achieve you Engine's spec. with this prop-I think it is 4600-5000 for the MPI.
Two big guys and a full tank is a lot of weight-it may change quite a bit with a lighter load.
Good luck.
I'm in the middle of a possible prop. switch and I feel your pain because I'm nervous about pulling the trigger and not getting the results I want.

[Miles Offshore]

"Two big guys and a full tank is a lot of weight-it may change quite a bit with a lighter load."

Gotta agree with the above Rip- 100 gallons of fuel= 800 lbs?, 2 guys at 250= 500lbs? 1300 lbs is right stout- the better numbers i had gotten were running with light fuel(~50) and just me(~195 ). I do feel your pain !!!!!! Do you normally carry full tanks? Not sure how far you are running but I wish I could afford to keep mine full,lol) I am hauling my ride this weekend and playing with mine some more-.

[riprunner]

I did the test with full tanks to represent a few customers on the boat. The goal is to have a low 20 knot cruise with 4 people and tackle aboard. I am now sceptical of this happening know matter what prop I go with. I'm starting to wish I put a Yanmar in there when we re-powered.

[Miles Offshore]

Got to agree with you on that rip- I dont know if you can get those kind of numbers with 4 adults and medium fuel on board with gas power although Gary might differ. I am hauling mine tuesady and getting rid of the keel on mine in another effort to both increase numbers and manueverability. I think it hinders control in larger beam and following seas and is a barnacle "magnet". Im well into the 1K range on playing with wheels now and said Ilast year I was done, yet contiue to be a glutton for punishment.

[riprunner]

I did charters both Saturday & Sunday one with 4 people and one with 2 people and my numbers are still almost spot on with my 15x17 wheel except I get more cavitation from the larger wheel. When I pull the boat in the fall I'm going to go back to the 15x17 and keep the 16x17 as a spare.

[ericminnig]

don't know if this is any help to you, but on my septre i run a 16rx19. i have a 350/325hp carb. at 2700rpm i run 23knots at 3200rpm i run 28 knots. if u live in jersey come for a ride. good luck.

[Miles Offshore]

put mine on the railway and pulled my new wheel again- going to run the numbers with the prop guy and see what he comes up with- im thinking 15-16 to get my rpms back up where they belong- ill see what he sez tomorrow

[PipeDreamsMarine]

I've played with a lot of inboards over the years, but never a SeaCraft. Most of the 23's have tunnels right?. How much space do you have between the hull and the tip of your wheel. It should be at least two inches or more. Most of you are runnnig 16", wheels has anyone tried a 15" or 14" with say 18" or 19" of pitch. I think the vibration most of you are feeling is from the wheel being too close to the hull and it causing cavitation and loss of push. The cleaner the water flows thought the tunnel the better your wheel will bite and the faster you will run. I also feel that if you could move the rudder out of the tunnel and put it off the transom (like Cary and Blackfin did) you would gain more speed also.

[GetReel]

Well the IB prop questions never get fully resolved and its slow at work....most of the wheels run are 16 as Don stated. I tried a 17 and its too close to the prop pocket hull walls and REALLY loud prop rumble that is a headache, although the boat moves better. The 16 is about 2" off the wall and the max diameter you can probably run without an earache. If you are getting 18 @ 3000, thats about average with a full load. My question is what are you running at 3250?...I get about 21.5 @3250 with decent load with a 16 x 17 4 blade 5* cup. Thats the best you can hope for unless you start again with a smaller wheel and way more pitch...not sure you will get more speed, but may reduce the prop rumble. THe Blackfin offset is great until you loose an engine and then run in a circle, assuming you have twins.