Heres the story...I have an 86 scarab III, had 454's. Upgraded to 550hp 502's over the winter. I'm running labbed mirage 23 plus'. I can get them to 5200 rpm with plenty of throttle left but I keep blowing out the port prop so I can't get an accurate max rpm reading. If I had to guess I would say I could get 5500 easy, maybe 5600. Is it time to go to a 4 blade like a hydromotive? If so where do I go in pitch? Or do I stick with a mirage and just bump to a 25? I'd like to prop it for 5200.

TRS drives, 1.5 gears, 62 on GPS which equates to 18% slip. With bottom paint on the hull the slip number doesn't surprise me.

I've got an email out to BBlades, but I thought I'd see what the OSO crowd had to say.

Kris

Kris, try 25-26" pitch Hydromotive Q-4's They work really well with the TRS, Julie/Matt @ Throttle up can help, If you were closer I'd Let you try my 27's When I went from the stock 502-415 hp to the 177 blowers, I went from 22'' to 27-28" hydros..Dave keep me posted !

Yeah Dave, I knew you've had good performance out of the hydromotives which is why I thought of them. I have not heard back yet from bblades, so I may give throttle up a call. Do they do a test program?

Here's an update:

Got a pair of labbed 26p bravo 1's from a local guy to try. Spun them up to 5000 easy, top speed was 59mph. How did I lose 3mph at the same rpm???? I understand the 4 blades are a little different with stern lift, etc, but losing 3 mph at the same rpm? That doesnt seem logical.

four blade are slower than 3 blades but handle better in my opinion

Ok,
first, who Labbed the 26 B1's and for what application. Labbing isn't a one size fits all like it was back in the early 90's when I was working at Mercury Racing. We now do it specific to the boat and the owners desires.

Second, I looked for a email from you and came up short. Did you recieve one? It would explain why I can't find it at this later date. (some time stuff end up in junk mail).
Also, nobody has a test program like we do.
Let me knoe if we can help.

Brett

I was told Mercury labbed the props and all he said was he told them he wanted an extra 400 rpm. Not much info other than that.

I got the boat out in some more ideal water and got it up to 61 with the bravo's. We did have a lenghty email thread, the last one I sent was on 2/25/10 when I sent my 23's into you.

I actually ended up buying the 26's from the guy because he only wanted $500 for them. I really like the way they get on plane and I have decent top end. I figured worst case I can get my $500 back out of them.

Also, before when I thought I was blowing out the 23's I think I have a tranny issue, and I don't think it has anything to do with the props. I'm going to get my tranny's rebuilt this winter then in the spring I'll be able to test these props better at max rpm and see the results.

Thanks Brett

Sounds good.
Keep us informed.

Brett

Kris,

Some additional info for you. I have 565hp 502's in my scarab. I am running 26p on trs 1.5 with bw. The current setup turns my engines to 5200 and 73 on the gps. 5200 is about 500 rpm's outside my peak torque. I am looking to borrow a pair of 30p and hopefully turn the engines in the 4700-4800 range. Now my current blades are 3 blade and when getting on plane I need to always bring the port engine up a little ahead of the starboard (300-500 rpm's) or the prop blows out. Since I read your posts I was surprised to see you lost mph with a 4 blade. I wonder if I should stick with a 3 or try a 4 and sacrifice some mph. I will let you know once I locate some 30's. What kind of speed were you looking to get?

Thanks
Jim

502ss, do not prop to peak torque. You will torque load your engine and wear it out real fast. We tore down a pair of stroker 496's with only 50 hrs on them and they looked like they had 500hrs on them. The rings were worn out, cylinders bad, and the mains looked horrible. The owner threw some 30's on it and ran at 4600RPM, cause he liked the cruise speed at 4600. You want to prop just a little below peak HP.

I am spinning 25 mirages (tons of cupping added) 5800RPM almost 78mph. I ran some 27 4 blade hydro's but they kept blowing the STBD prop out at 4000RPM. I didn't try any speed runs but eventually pulled 5200 with throttle left. The boat ran with a lot of hull in the water. I am now trying to get some 26/28 bravo1's to try. The 3 blades carried the bow much better and a smoother ride, that's why I want to try B1's cause the hydro's lift the stern.