Propping a 28 Cig

[Tony]

After two years of wrenching on this pig I'm finally getting a little bit of run time on it. The boat supposedly weights 5k dry, and I lightened it up quite a bit by using aluminum heads manifolds and exhaust. Engines are SBC strokers making a little over 400hp in front of BorgWarner/TRS drivetrain. Over the past few years, Ive scrounged every corner of the net trying to find a starting point for props and decided to start with 25 mirage+. Running the boat last night trimmed to the moon and stretching the throttle cables I managed to see 4200 RPMs. Am I way off base here, or should this setup have no problem hitting 5k rpms?

[jhenrie]

23? I and a bud have 29 scarabs w/ small blocks. , mine 270 350 mags , my buds , 300 mpi mags. I run 23 laser2 on my alphas @ 4800. My bud runs 23 m + and runs right @ 5000 on the mpi/bravo setup . My bud just got a 28 powerplay with 350 mag tbi small blocks and needs to mess with props , runs bravo 4 blade now but I think he needs the mirage+. If you are making 400+ hp the trans and trs must be killing you. What kind of speed were you seeing with the setup you ran?

[insanity]

How deep are those TRS below the bottom of the boat?

[FULL FORCE]

I think the deep TRS make it hard to spin bigger props unless you have tons of power, just like my boat, I cannot spin more then a 23 past 4900-5000 and I have 450+ HP, Dave's 311 with Bravo spins the same 23 at 4700 with bravo with 365hp..

I now have a set of 23 Mirage + if you want to try them out, I will up at Marblehead tonight if you come out tomorrow

[FULL FORCE]

what props were they before and what rpm? you had 300 hp a side before right?

[DonziGirl]

I think the deep TRS make it hard to spin bigger props unless you have tons of power, just like my boat, I cannot spin more then a 23 past 4900-5000 and I have 450+ HP, Dave's 311 with Bravo spins the same 23 at 4700 with bravo with 365hp..

I now have a set of 23 Mirage + if you want to try them out, I will up at Marblehead tonight if you come out tomorrow

I might give them a try, wont be up until next weekend though. Ive done a good bit of searching on guys running TRS 28Cigs and 25 doesnt seem too far off, I read a post where a guy was running stock 7.4 (heavy azz motors) 310hp. and spinning 27 mirage+ at 4700. Granted theres a little more torque in the BBC but still.....

[Ratickle]

I'm sure you weigh more than that Tony. The 377 Scorpion with Bravo is 969 lbs. The TRS and Trans adds around 200 per side to that.

Have you got a centerline on your prop to bottom yet? My guess is you are overpropped with your setup. I have the same problem on my Scorpion 39 with the 540's. Cannot spin a big prop like a Bravo in the same setup will.

[FULL FORCE]

I might give them a try, wont be up until next weekend though. Ive done a good bit of searching on guys running TRS 28Cigs and 25 doesnt seem too far off, I read a post where a guy was running stock 7.4 (heavy azz motors) 310hp. and spinning 27 mirage+ at 4700. Granted theres a little more torque in the BBC but still.....

I just wonder if the small blocks loose too much torque up top where a BBC will not lose as much to keep a big prop spinning, I also have a set of 23 quicksilver labbed to a 24, may be just right too, you can try those too if you want just let me know so I can bring them, I plan on trying the 23+ on mine this weekend, but I cna yank them for you to try next weekend if you want.

[FULL FORCE]

what was on it before? rpm max?

[Ratickle]

By the way Tony, GPS speed at rpm and prop size/pitch.

Several bench mark points if you take it out. And trim it differently at the RPM you choose to see what it is doing to speed. Always mark the same trim, speed, rpm on your log so you have the perfect benchmark spots.

[mbam]

Back in the day one of my buddies had a 28, we had converted it from Volvo to TRS (first time I ever plugged a transom) and put the drives up into the rub rail. 400 CID small blocks, dynoed @ 400 HP. Ran the fastest with the old Merc cleavers. Ran 23" @ a little over 6000 RPM

Any of the old-timers from Chicago might remember it, boat name was Leda

A few years later I did a 28 Magnum (standard drive height) for a customer and did some back to back testing. The cleaver was still the fastest, Laser was second, Mirage was off 2-3 MPH. Ran 70, I think it had 21's

[northernoffshore]

Mark is right, they like the old style cleavers . try to find a set of 25 pitch . hydromotives work also.

[northernoffshore]

http://motors.shop.ebay.com/i.html?_nkw=cleaver+props&_sacat=26443&_trksid=p4506.m270.l1313&_dmpt=Boat_Parts_Accessories_Gear&_odkw=&_osacat=26443

[ROGUE]

Ive got a pair of 21's from when my tank was stock you can try if you want to. I think the small blocks have got to turn some rpms to make hp as they dont have a lot of torque especially on the heavier hulls.

[Tony]

Ive been hunting for a pair of 25 cleavers for a long time. Seems like everything Ive read about with the same setup is hitting top speed with cleavers, despite the fact that its old school technology and the drives are super deep. I've got a pair of 21 cleavers that Im gonna bolt on and see what happens.

[FULL FORCE]

Tony, I also have a set of 23P 4 blade Hydromotives...

[ROGUE]

Ill bring the 21's down to the marina this weekend and put em in the dock box if you end up here and want to try em.

[Tony]

I have a set of 21 cleavers, but thanks anyway Tom.

[J-Bonz]

Yeah, thats the pitch of the pair I have to.. Hope they work for ya.
Jr.

[mbam]

Those old cleavers came in 2 flavors, the real early ones had too much blade area. I doubt if there are many of those left.

How much power do you have and how many RPM do you want to turn? 25" seems like a lot. How fast do you think it will go?

[VetteLT193]

The weight sure seems low. My 28 Donzi ZX weighs 6500 dry with small blocks/bravos. I'd think a cig weighs more than my boat.

How was your power rated, at the crank? with Marine exhaust or headers? etc.

Considering I have the 377 MPI's @320 HP and a twin step bottom it makes sense you'd be running smaller pitch props. I run 26 Bravo 1 or 25 M+ with 1.65 Bravos. If I had 1.5 Bravos I'd be down to 23" M+'s.

I'd think based on your current numbers 21" M+ is where you'd be to get your RPM up to 5200.