Formula 242 LS Prop questions
 

Hey guys,
I'm new to the forum and this is my first post.
I have a 242 ls in excellent shape, so when the motor was acting up this season I decided on a full rebuild. It was originally a gen 4, 454 magnum with GIL exhaust and survived 934 hours in Salt water.
I rebuilt with new DART heads a HO Holley marine carb , different cam ,punched out 30, polished and balanced the crank and new exhaust. When it was all said and done the motor made 526HP on the dyno and 558 ft/lb of torque. It had a very impressive torque line for a 454 truthfully.
My question is where do I start for propping. The boat used to run anywhere from 55 MPH to about 60 on the gauge originally with a SS 21 pitch mirage plus. I know i will need to increase in pitch, but I'm wondering if a 23 might not be enough. I have my sights set on a mirage plus 25 Pitch but I'm unsure. From most of the research I have been doing its suggested that these big old boats prefer a 3 blade prop. I am hoping to see 70MPH or just slightly above. I do pull the occasional skier or tube as well though. My engines performance max's out at 5300 RPM.
So I now have an additional 300 or so RPM to play with as well another 150 some odd horsepower. I would really like to stick the landing on the prop lol.
Any suggestions would be greatly appreciated
Cheers

A buddy with a 242ls dynoed his motor at 490 horse. Boat runs very close to 70 with a 23 mirage plus at 5400ish. We tried a 25 + and that brought him down to 5k and was a couple mph slower back to back testing. You have more power so should turn a 25+ pretty good. If not the 25 could be tweaked by a good prop shop.

Prop Questions
 

Thanks for the info,
The guys I run with have a 23 foot Baja 470HP with a 24 pitch 4 blade, runs 68mph, the other has a 26 4 blade in a campion chase with a 500 HP,,,runs 74mph. They have told me I can try their props in the spring but Im told that my heavier boat likes a 3 blade.
The Mirage plus 21 was perfect for the stock magnum in my boat, I could reach my peak RPM at 5000, now I am able to run 5300 RPM with with an additional 150 HP or so. If I go out and buy a 25 Mirage plus i suppose I can always have a prop shop tweak it down a bit to get me closer to a 24 or so.
Im wondering if this might be my best option

So your turning the 21 at 5300 with the new engine? What speed? With 526 horse you should be turning a 25 close to that rpm and way over revving a 21.

Prop talk
 

Sorry about the confusion, What I meant was with the 21 and the original magnum (365) with GIL exhaust it used to turn at 5000 RPM. That was perfect for the old motor.
Newly built motor is 526 HP so the 21 pitch is definitely no good to me anymore.
On the Dyno my newly built block (526) hp made its peak power at 5300 RPM....so that's where I want to be when I figure out my propping. I never got a chance to go for a run with the new block yet.
I'm more or less looking for a good baseline to start with, and from what I'm hearing and seeing on these different forums is that a 25 mirage plus might be the right fit.
I just don't want to waste money on a 23 pitch and then be under propped.
Cheers

Ahhh, gotcha, both will be close, but I bet neither perfect. That being said I think either can be tweaked as needed to dial in.

Thanks for the info, I think Ill start with the 25,,,maybe I will get lucky. Either way the old girl is gonna be some lively in the spring. If its too much I will take it to a shop and have it tweaked a bit. The shop that dynoed the motor was some impressed with the torque it produced... wasn't much of a curve,,,,more of a flat line. I'm hoping good torque will spin the hell out of whatever I put on lol

My guess based on your power number and my knowledge of that hull is 70-72 at 5200 with a 25+, if it won't quite turn the prop you can have it labbed. Let us know the results

https://m.youtube.com/watch?v=DH39taG2bxE

Here is the boat right at 70gps

Hey everyone, finally got the boat out for a run, I cant seem to hit the right RPM's with the Mirage plus 25 pitch Im hitting about 4400-4500 or so, going to try a 23 Mirage plus and see where I end up. Im guessing I overpitched a bit out of the gate. I will post results with the 23.I would like to see 5000-5200.

I run a labbed 21 4 blade and would never go back to a 3 blade on this hull. Slow out of the hole and cruise was terrible. Gained 2 mph having it labbed also. Im not bone stock but even when it was the 4 blade was much better.

Thanks for the reply. I plan on dialing it in the next time I get home from work. I have the 23 mirage Plus I picked up and I will probably trade the 25 Mirage plus I have for a 22 4 blade Bravo 1. I always had pretty good luck with my 21 Mirage plus when it was the stock 454 magnum with GIL exhaust.. Did lots of skiing and tubing and it was perfect RPM wise. I used to see 60 on the gauge with the 21 WOT and all trimmed up. I jumped up another 150 HP with the rebuild but I went right to a 25 and it seems a bit much. The 23 I picked up should put me pretty close to where I want, and I will trade the 25 plus for something else in the right range. At least I will have a good spare with the mirage if I get a nice 4 blade as well.
I have 2 buddies one has a 22 4 blade,,,,the other a 24 , they will let me try them out so I can get dialed in. The 22 im guessing will be to little...but it dosnt hurt to try
I was a bit disappointed with the 25 at this point. I have only been out for 2 very quick runs however. A little bit more time and I will have it sorted