Prop for 23' Inboard Re-Power
 

What is everyone's experience with props for 23' inboard? Just repowered a 23' with a 300HP mercruiser with 1.5 to 1 gear and 1-1/4" shaft. The old prop was a 15-1/4x14 3-blade. Have been told to go to a 16x16. 4 or 3 blade?

Re: Prop for 23' Inboard Re-Power
 

My records indicate the original spec was 16 x 17 3 blade with 5* cup and that's what was on mine. I am running a 16 x 16 4 blade on the same 1.5 gears. Max wheel size is 16 or the prop rumble will be overwhelming. I like the 4 blade, but you'll have to buy it 17 and have it cut down to 16 x 16, they didnt make a 16 when I did mine.

Re: Prop for 23' Inboard Re-Power
 

What kind of speed and rpm performance are you getting with the 4-blade. Thanks for the response. Appreciate it.

Re: Prop for 23' Inboard Re-Power
 

I'm running a 16 x 15 with a cup on mine.
Power is a 350/260hp Marine Power with efi.
My most efficient cruise is at 3400 RPM and 23 knots.
wot is 30 knots.
Curious how the extra hp moves the boat.

Re: Prop for 23' Inboard Re-Power
 

Also about the 3 vs 4 blade

Re: Prop for 23' Inboard Re-Power
 

CValle,

The whole time I have had my 23 inboard I have not been happy at all with the performance. I started with a 15x17 and moved to a 16x17 per the stock specs and got the same exact poor performance. I was working the top of the engine too hard and wasn't getting anywhere near max RPM. Last fall I sent the prop out to Yohan in New Bedford and he changed the pitch and must have sprinkled some pixie dust on it. I only had a chance to take the boat out for a 20 minute run afterwards because it was the end of the season It was like a different boat, quiter, faster, more responsive, and better on fuel! I can't believe how much difference it made by making adjustments to an existing prop. I'll be back in hopefully this weekend, I'll post my new results soon. I'm located in Falmouth innner harbor next to pier 37.

Re: Prop for 23' Inboard Re-Power
 

Mine has a 350 CARB, 315 HP and I have a 16 X 16 with a little playing with the cup to get the correct RPM 4600.
I usually run at 26 around 3100 RPM and 37 wide open with 3 people on it and get on the offshore trips for wreck fishing (don't usually turn it off unless I have another boat with me)I have gotten a lille better then two miles per gallon.

Re: Prop for 23' Inboard Re-Power
 

Gary,
Is that 26 knots or mph?
Either way, it's good. The extra hp makes a difference.

Re: Prop for 23' Inboard Re-Power
 

@6 MPH, I use that because the couple of friends with SEE Vee's and SEACRAFT's ask what MPH and RPM's I'm running.

Re: Prop for 23' Inboard Re-Power
 

You and I are about the same. I'm not sure about my Hp. I thought I was lower (2V carb) and my speed is a little slower than you but I also get just over 2 mpg. As for my prop size - I have no idea other than 16". I want to change it for some stern lift and try for a little better milage so I am very interested in this discussion.

Re: Prop for 23' Inboard Re-Power
 

I'm also very interested in this discussion. We are a rare breed as there were only about 80 inboards produced in the 70's and we are among the last ones standing, or floating I should say.
Mine is a 1976 that originally came with a Ford 351 which was tired by the time I got it in 1992.
I re-powered in 1995 with a Marine Power 350/260 hp with throttle body fuel injection. I tried multiple props and settled on the 16 x 15 with cup as showing the best numbers. Fuel consumption has always been 6gph or less.

Re: Prop for 23' Inboard Re-Power
 

I have A 454 Marine Power 330 MPI / FWC installed 2001. Actually just rebuilt last year. The original was the Ford 351 LH 1.5 tranny and burned about 8 gal per hour per orignal owner.

My numbers are about the same as those most have, 3250RPM cruise gets me about 19.5 - 21.5 knots depending on load and wind/tide variables. I hit the top end at about 30 knots at 4600/4800 RPM WOT. I can cruise at about 3400/3500 at about 22.5 knots but thats not her sweet spot. I dont really track fuel burn much but I would ball park 12 gal per hour full load for the big block appetite. I can go about 35 off with spare fuel leftover and make it back by keeping her at 3000 and 19 knots on the way out with full load and not pushing too hard, drop in lines early, troll back in etc.

I like the 4 blade for improved hole shot and I think also improved slow speed handling, although, we all know backing this boat up can be humbling. I just had my prop reconditioned and last year I did epoxy barrier coat job and I think I have picked up 1.5 knots on that.

Good Luck.

Re: Prop for 23' Inboard Re-Power
 

I stand corrected the prop I have is a 17 X 17. My fuel gauge at 3100 read's I'm using 9.5 GPH. I do turn 4600 RPM.
I guess being retired and old I need to double check things more often.

Re: Prop for 23' Inboard Re-Power
 

Mine is a '75 Sceptre inboard, Marine Power 350 - 4B Carb 260HP

16 x 16 cupped

2700rpm - 20knts (most economical cruise - I think)
4000rpm - 30knts

Re: Prop for 23' Inboard Re-Power
 

I have 78 23 sf inboard- 350 mercruiser -260 hp- bw 1.5=1 tranny, 4 brl.
16x15 cupped

2800=21kts=8 or 9 gallons an hour depending on tide
4000=30kts

I don't think it gets any better unless u have 330 mpi even the 454's do not have anything on the 350.

Re: Prop for 23' Inboard Re-Power
 

I know the 350's are lighter then the 454's and I do get a little rumble in the bottom with this prop. The 350 fuel injeted when I bought mine was 330 HP @ 4800 RPM and my 4 barrel needed to turn the 4600 RPM to open about 3400 RPM and I have a fuel monitor and a GARMIM 2210 also tabs and I try to stay under 10 GPH since anything more is about when the 4 barrel kicks in and I hit 37 top end (MPH), it handles way better then the 233 HP 351 I had. The hole shot is great.

Re: Prop for 23' Inboard Re-Power
 

I should hopefully be back in the slip next weekend. I took some extra time doing things this spring I know I wouldn't when she's in the water. Last fall when I did a test run after the prop work I think I was turning 4500-4600 rpm. I will check my top again to be sure. I think I need to tweak it to run 4800. I am running a newer MPI with big hp, but I also have a very tall t-top with that is fully enclosed with a 4 foot open array so I'm sure I have more drag than most.