lab props
 

i have a 26 foot ChrisCraft Scorpion with twin stock 260's and alphas. this winter i am putting on carbs/intakes/cams/exhaust. mild stuff probably bring em up to about 325's or so. i am currently running 23 inch quicksilver mirages. last year i knew they were to big for the boat as the best i could spin them to was about 4200rpm. i am hoping to be able to spin them with the mods i am doing. my question to you . . .the all knowing OSO tech squad ;) . . . .will i be able to benifit from labbing the props with this mild combo? i am planing to have the props re-con'd but dont know if spending the extra $$$ for labbing would be worth it.

best bet would be to GPS the boat now, then do your engine mods , break out the gps again and see what speed and rpm increase you picked up, you can call a good prop shop then and they can help you on your slip ratio and what a lab job would do for you, if you are after that last couple mph, then a lab job would help.

thanks H2X. i am seeing 55/56mph at 4200rpm WOT. that is with the stock 260 hp mercs. like i said i know i am over propped so i am hoping that by adding 50 or so HP per side i can spin them up to about 4600 or 4700. not really looking to squeeze the last mph out of it but if labbing would be worth it in a modest performance like my boat. a friend of mine picked up like 3 or 4 mph by labbing the props on his 38ZX. i know thats a whole diff ball game but if i thought i could pick up a few mph i would consider it. i guess I'm just wondering if the gains can only be utilized at the higher end of the scale. thanks again

Dave, I have a set of 21's you can try if the 23's dont work out. Oh, are yours counter-rotating?

Dave, if you can get on plane ok with those mirages, then your x-dim is too low. You'll find a couple mph in going higher. The question is how to do that with alphas.

formula- thanks for the offer. i was thinking of trying 21's. they are both right handers though. what kind of props are they?

cord- actually that thought crossed my mind. being a glass guy it is somthing i can handle. only problem i have now is i only see myself in this boat for about one more season, not sure how badly i want those last few mph :D. you mentioned geting on plane with the mirages. are you saying these props are happier closer to the surface? right now the x dim is very low. is there a better prop for my application? thanks

GLASSDAVE GO ACCLERATOR
 

DAVE,you can stay with the 23 pitch props and have them re designed to the ACCLERATOR PROP,This prop design allows you to plane quick,with no or very little cavation and midrange is awesome,and the props that we have done our customers are getting a solid 2.5 to 3 mph on top end .give me a call or p.m. me and I will hook up you up as far as the price and in the water:D .here is a picture of a mirage converted to what we call the ACCLERATOR.

ACCLERATOR DELIVERS AT BOTH ENDS OF THE SCALE.
 

here is a right hand ACCLERATOR,Also if any pitch changes where needed in the future we will do it at no charge,but in the ACCLERATOR THE 23 PITCH WILL WORK AND RUN THE QUICKEST.If you have any questions p.m. me and I will gladly call you,Thanks Darin

Glassdave,

There are a few things to keep in mind. The new cam shaft will pretty much dictate at what rpm you will have to run the motor to obtain max HP. The other improvements you mentioned will all improve HP at higher rpm. Your 260 HP motor should be between 4400-4800@WOT. With the work you have done to the motors you may need to run above 5000@WOT to obtain the best top end speed. Since you don't have dyno numbers on the motors the best way to find out what rpm to run is to put different pitch props on and see which rpm gives you the best top end speed.

With the work you have done to the motors I think you may see an increase of rpm of about 300-400 rpm. You may see very little rpm increase, however. It all depends on the camshaft. I doubt the 23's will work for you. You probably have to be in 21 Mirage's (not Mirage Plus') to get the rpm up around 5000..

With the standard Mirage it's really not worth lab finishing them. I suggest having them checked to see if they are true. If they are have them cleaned up and they will run great. There really isn't a lot to gain with the old style Mirage through a lab finish, if they are true.

The best thing to do is the run the props you have now and go from there. If you have any questions feel free to call.

Matt
877 842 6855 toll free

Dave, well mine are left and right so I can only help you with one but there should be plenty of 21 Mirages around

Glass-I've found the mirage to be one of the poorer planing props when the x-dim is high. I know that cat's like a high x-dim, so the fact that you could even get on plane with a mirage told me that your drives must be deep. Many stern drive cats like the bravo 1 prop. What is the cut down version called? The revolution? Anyways, if you were to raise the x, then I'd be looking at the rev. Until then, I'd proably just stick with a 3 blade round ear (especially if you are looking to get out of the boat).

thanks guys, great advice! . . i just got back from skiing this weekend so i wasnt able to catch up on the thread till now. i am going to do somthing with my current props in the next few weeks. they have a few dings and need to be gone over. the accelerator sounds very intriguing. i have heard good things about that service. actually i really like these quicksilvers i have now. they cary the bow real nicely. i love the attitude i get out of them but like i say i can only get em up to like 4200.



throttleup- you make some good points. i may have to research some cams a little more. i was basing my upgrades on a similar motor i did for a 24 foot Mirage i had before this boat. i will probably do some prop testing this summer. i was thinking i should run these to about 4600rpm. they have about 400 hours on them and are in great shape. is it ok to run the stock merc long block at 5000prm? i dont plan to run it on the pins all the time :D mostly just to maximise what i have to keep me happy for another season or so. thanks

Glassdave,

4600 would be a good rpm for the stock motor. But to get the most out of the upgrades you have done you will need to get the motor running at it's peak HP rpm. Without any cam information it's hard to tell what rpm your new motor needs to run at.

We just went through a similar situation with a local customer. He had an HP500 and rebuilt the motor but changed the cam along with some other parts. When he was done the boat was slower than it was stock. When we got him propped out to run at 5800 he picked up speed over his original motor. He didn't want to have to run at 5800 so his only other choice was to change the camshaft. Make sure the camshaft will work properly at the rpm you want it to.

As far as the durability of your motors we wouldn't be the ones to say if they will hold up or not. We only work on props. With all the high performance boats we work on we just make sure the props run at the optimum engine rpm. Whether the motor will hold up at higher rpms, I really couldn't tell you.

Matt

thanks T-up. actually i havent done the motors yet ( still to dam cold here :D ). i have just rounded up all the parts although i think i will need to look into my cams a little more, may hafta start a new SBC cam thread :D . . . Dennis Moore!! . .help!!!

Glass,

A while back, I had a CC 260 Stinger with stock 260's and Alpha's. I ran Merc Mirage Plus 23p props and loved them. It ran 4900-5000 at WOT and topped out at 60mph. The thing I liked about them is that from a standstill, I could tuck the drives, and literally jam the throttles without a lick of cavitation. When running poker runs with bigger powered boats, this is a big advantage to get out into clean water before the wakes are everywhere around you.

I still have these props sitting in the garage if you're interested. Excellent condition, both RH rotation. I'm in Gibraltar, MI, so they would be easy for you to take a look at. I can also email pictures.

Just giving you options....

Good luck,
Brian

P.S. What year is your Scorpion? My Stinger was an '88, so I don't know what, if anything, Chris Craft did to the hull performance wise between the two models.

I just re-read this post and I am a bit confused why you're only seeing 4200rpm with your current 23p Quicksilvers. Something doesn't add up. I just went out ot the garage and double checked that mine are indeed 23p, and they are.

So the question is - Did CC make big changes to the hulls between the Scorpion and the Stinger for better performance? Is the Mirage Plus prop that much better of a performer than the Quicksilver?

Maybe the OSO gods can shed some light...

Cheers,
Brian

Last question...

How many hours are on your motors? Mine were brand new, and I put probably 200 hours on the boat. Is it possible your 260's are "tired" and not getting the power that they used to? You might want to do compression tests and leak-down while the motors are apart.

Brian

p4-33- thanks for your input. i always like to hear how other owners ran. my boat is an 85 with good power they run well with about 400 hours on them. i got it from the original owner who i have known for years and know they has been well cared for. i think my boat is a bit heavier than the later years, they did some revisions in 85/86 and refined the boat a bit. most owners i know with the same hull are running 21's with stock 260's. the 23 QS's i am running now work real well, no cavitation or blow out at all. mechanically the boat is great. my original thought when i put up this thread was that i am needing to get my props cleaned up and if labbing would be worth the extra $$ at that time. after i do the engine mods this winter i hope to be able to spin the 23's better. i know will hafta do some testing and would like to contact you on the props you have. mine are both right hand also. thanks again Brian.



Great info guys . . this is why i am a member. :cool: :cool: :cool:

Hi Dave,

When you're ready, send me email at [email protected]

Good luck with your motors.

Brian

One more...