Maximum inboard prop diameter
 

Anyone know for sure?
I know they "growl" a little but want to maximize efficiency.

:confused:

I ran a 16" on my old 23. I think the stock one was 16 x16. I don't think you could run a 17" wheel as its to close to the tunnel and would cause cavitation and a bit of noise. The CC26's run a 17" but the tunnel is much bigger or wider and the shaft angle is slightly different. The 26's also had a cavitation issue with some noise also did not like to turn to port at speed.

I managed to get the prop from the previous owner, 17 x 17 3 blade. I now have a starting point.
So. I am really close to the engine decision. I believe it will be the PCM 409hp beast.
Prerequisites were, fast and clean. I really like the cooling system on the PCM. KISS theory!
I want to be able to "loaf" along at about 25 knots without a horrendous fuel burn, but have a little sumtin under the hood for when one of those pesky outboard fellas pull alongside.
Did i mention fast?

i run a 17x15 with some cup on mine and it does very well, plenty of clearance to hull.

If you dont mind me asking, would you share your gear ratio, HP of motor and cruise/WOT numbers please?

power will have to be increased exponentionally to gain speed...


there's no way a 23 inboard will run with the go fast outboards,such as the contenders,yellowfins and jupiters - ain't gonna happen...

smart move:

repower with a new merc 5.7 horizon,use a 1.5:1 zf gear and be done with it

it's gonna prove to be reliable and incredibly fuel efficient

the boat will run a real good speed with that power - and the best part:

it's an easy install/set up


if you want to run with the fast outboard rigs - get one

trying to make that inboard run with them is going to be like finding bigfoot - a dream...

I'm not sure about running with the new go fasts. I want to see a solid 40. Fast for an inboard.
I will routinely carry 5-6 people and a large cooler of water/beer!
The Sea Craft 23 inboard was fairly popular here. For a small island, I can count 4 without thinking about it much. I know 2 for sure have inboard Volvo Diesel and are pretty tired.
None are restored.
I'm trying to be a little different. My nature!

I ran a 17-17 for a while on mine but the old 260 hp was just not enough to spin it in the proper rpm range. Also tried a 4 blade 16 i believe and that was a waste of a grand too! Lol. Worked my way back to i think im turning a 16-15 now and that worked great with the old motor. Going with a new vortec this time so i will see how it does with an extra 50 ponys.

Ive got a fuel injected marine power 350 with 315hp and a 1.5-1 zf gear, cruise anywhere from 20 to 27mph depending on seas, seas here on the cape are generally crappy and the boat will cavitate a lot if you don't bump it down. if you want to run 40 go with the outboards

That cruise sounds great. What wheel are you running?

wheel is probably a 16x15 with a big cup

the newer MPI motors have the torque to turn a bigger wheel

older 260HP carb'd small blocks should be running a 16x14 with a cup

allways want a cupped prop - the cup acts as a little more pitch and it holds the water - less cavitating

With a nicely shaped 3b 16x16 and a 260 hp motor, you should cruise at 20 kts, and top out at 28 kts, depending on a whole lot of stuff.

But the unvarnished truth is that you're not going to touch 40 kts without at least 500 hp, (and probably not even then) simply because of your angle of thrust.

Too much wetted surface=too much drag. You'd have to fair your tunnel, then extend the shaft and rudder out of the transom to get the thrust angle within about 2-3 degrees of your keel line. Too much continual stern lift results in too much forward water displacement resulting in too much drag.

I knew a 23 inboard in North Palm Beach that was repowered in the 80's with a 375 hp small block, and she topped out at 31 kts, or 36 mph. That long-duration cam sounded great, and it nearly jumped out of the water from a stop, but the laws of physics still prevailed.

Thanks for the input.
I will likely stay with the PCM 353.
The torque from the watercraft motor will give me what I want for the cruise.
The wot remains to be seen at the end of it all!
I have been using the spec sheet for the calculations and the following link.

http://www.vicprop.com/planing_size.php

17x17 prop 454 inboard 23'
 

I had a 17x17 prop on a 23' cc with a 340hp 454. Ran great, awesome control at low speeds and insane hole shot. Clearance in the pocket isn't an issue, no turbulence at all.

Right now with an unknown hour 351w with probably 235hp I’m seeing a cruise of 24mph, a top speed of 32mph. This winter it’s getting pulled and rebuilt to add some serious horsepower to it, with this being said, I don’t see how with 130-160 more horsepower I won’t pick up speed, EVEN if I have to change the pitch and add a trolling valve.

Think Big.....
 

If I was to ever own a car engine boat it would have one of these.

Amen to that