Help with Solas Prop selection

[Trouble11]

I am wanting to try a new prop for My boat. I have a 23 foot Performance boat with a Bravo 1 out,drive, and a 502 Mag, 400 HP at the prop. I currently have a 23 Pitch Mirage and turn the boat at about 5300 rpm trimmed all the way. The boat rides fairly well, but in the last bit of trim it will chine slightly. when I look at the Videos of the boat riding at full speed form a boat opposite, the boat rides and the attitude of the boat are good. The rated max engine speed for the boat is 5000. The boat currently does 64 mph on GPS.

I feel it is under propped. I am looking to increase my speed as close to 70 as I can. I know that for every pitch increase it will reduce my rpm's approximately 250 rpm.I want to try the Rubex L 24 4 Blade. I have read that the 4 blade can cause you to lose 200 rpm alone on top of the 250. The Rubex description for the L4 says it is a high speed 4 blade.

I am very hesitant to pull the trigger on the 4 blade, or a larger 3 blade maybe up to a 25 as once you purchase the prop you own it. My last performance boat I switched form a 3 Blade 23 pitch Mirage to a 24 Pitch. It made a ton of difference in handling on rough water conditions.

From my math, if I can spin the L4 at 5k rpm it should put me in the 68 to 69 MPH range, which is about where I want to be, plus f I can spin the 4 blade the handling would be great. 4 as a 4 blade for top end performance over the other Rubex 4 blades, or should I go to a Titan L3 with ore cup and rake, and can I get up to 25p or better with a 24p.

 

[porscheguy]

Do you have trim tabs? Trim tabs will help control chime walk. Trim tabs should be mandatory once you break 60-65mph.

Is your prop a mirage or mirage plus? The mirage has minimal cupping compared to the mirage plus. Where are you located BTW? I’ve got a 23P mirage plus with very aggressive cupping that I’m looking to get rid of and would let you try it if you’re close.

As for the 4 blade, what gear ratio do you have? As it is your slip could be anywhere from 8.5% to 25%. A four blade will have increased drag over a 3 which can result in lower speeds. The L4 description claims improved mid range performance. This doesn’t strike me as something that will get you to 70mph.

In summary:
1. Mirage or mirage plus?
2. Gear ratio?
3. Location? (Optional)

 

[Trouble11]

Porsche guy, Thanks for responding. The prop is an original Quicksilver Mirage. My chine isn't really that bad, and only does it if I am at the very top of my trim, in which case I may be over trimmed. My gear ratio is 1.5 to 1. I am located in the Seattle area. I am still wanting to lower the rpm, but you got me thinking maybe a 24 pitch 3 blade with more cupping and a better rake after reading some other forums. Really want to hit about 5k rpm for my stock mag 502. The engine runs great, and don't want to push the valve train. I don't mind adding trim tabs. If I get close to 70, good enough for me. I will never be the biggest or fastest .

 

[porscheguy]

Right now your slip is just under 17% and you’re overreving.

If you reduce slip through more agressive blade geometry you’ll also bring down your RPM and increase speed.

ive seen a slip of 6.5% on my 21P mirage plus with extra cupping.

Ive got a 23P mirage plus. When I tested it last fall, I was turning 4600-4700RPM. I sent it to the prop shop and had more cup added. It dropped 400-500RPM. I lost speed because I just can’t turn it. Your boat has 2X the engine displacement and horsepower as mine, so I doubt you’d drop anywhere near as much rpm as I did.

Personally, I’d go with a mirage plus 23P. Just switching to the plus should gain you a few mph and shave some RPM. If you want a bit more, you can have more cup added. The final perc here is that any prop shop worth doing business with will have pitch blocks for a mirage plus. Solas? Not so much.

sent you a pm.

 

[Faztbullet]

Better to rework your prop than a 4 blade as they are slower than 3 blades