Prop selection for 99 353 HP500 w/boxes?
 

I think the boat currently has the original merc 4 blade in 30P. I'd like to turn these into spares. Any prop suggestions for improvement without breaking the bank? Thanks.

I'd go with a set of labbed 28 5 blade Maximus. 15 1/4" diameter, with a little work, 5200 rpm's.

Dave

I read that these would create more stern lift. I'm no expert on this but wouldn't this push the bow down on the 353 who bow runs a little low already? How about the Hydromotive P5X? Some people claim they run as good out of the box without the expense of labbing the Maximus. Just trying to avoid a $2k experiment!

I have a s set of 28 pitch 15 5/8 5 blade maximus for sale in excellent shape

Did they actually make 15 1/4 and 15 5/8?
What boat / motors were you running them on?
Have they ever been repaired or reworked and why are you selling?

Snoboard - your PM box is full. Anyway, there are some nice programs out there now where they're offering demo's for a $40 turnaround fee. Merc racing prices are a bit high on the Maximus - you can get these from Mertinemarine.com for about $1080 each. I think I'm going to have my 4 blades tweaked to see what that does to the top end.

Yes but you may be able to trim higher and have the extra blade to "carry" the bow.

That was my experience with my 311 anyway. Yor hull may react different

Thanks, I had an older Wellcraft hull like the 311 and it was bow high most of the time, never had a chance to throw cleavers on. The 353 stepped hull behaves a bit different than the std. deep V's - I may try a little work on the 4 blades before going to the 5's.

Let us know how it works !:drink:

I never anticipated this much trouble dialing in my new setup. This year I have tried 30P Bravo 4 @ 5500 rpm 28P Bravo 4 @ 5700 rpm and 27P Mirage 3 @ 5850 rpm. I cant ring out more than 82 in salt water. It makes no sense considering we have a combined increase of 80 more cubic inches 186 tq and 270 hp on the dyno vs the original hp 500s but only picked up 3 mph. The new motors peak tq at 4800 and hp at 5800 vs the hp500s which maxed tq at 4300 and hp at 5300. I spoke to Brad at BBlades but we are all over the place with recommendations. He was thinking of having me try 5 blades but the bow seems to carrying to low already with the 4 blades. I wish there were some good shops left in NJ that did prop dialins and rigging.

So you have a 353 with 770 hp on boxes running 30P Bravos at only 82 mph. That's just a little more mph than the stock HP500's would get you.

I know you mentioned a dyno, but it almost sounds like you're not making as much HP as you think. Or, you're getting tons of slip because of those boxes.

I run 5 blades and Im working on 4 blades now. No boxes. The 5 blades do lift the stern, but getting on plane and mid range is great. The 4 blades seem to be a little faster but I haven't wrung it out yet. Based on my boat, you should be in the high 90's with that much power, although mine is a later model and I believe they changed the X in the mid 2000's.

Hope this helps.

Sorry maybe I misquoted numbers my old HP 500a were dynoed at 535 and the new motors at 697 corrected HP plus more TQ and CID. I did speak to the factory a few years ago about the higher X dimension but never got a confirmation that they actually did it even if they did the boxes would more than make up for one inch of x you would think. I might have an opportunity to try to set of 4 blade Hydro motives 28 which I think will be more like labbed Bravo 4 30s. The only other thing my engine builder suggested is having the hull checked for hook but that will be in expensive proposition to change if we need to get it blue printed

Offshore performance in egg harbor did a 353 a couple years ago. A guy near me bought it. Did you put raised boxes or straight? If they're not raised you effectively lowered your propshaft height. Formula raised the x dimension 1" on boats that got boxes from the factory.

Good to know. My boat is a 99 and the boxes were on from the factory. I'm not standing in front of it but I'm thinking they are straight.

Wete any of the boxes adjustable? I seem to remember reading about this at some point.

Stellings are adjustable. I have them on my 353.

Excellent, I'll have to check. Do you know how difficult the adjustment process is or if there any special steps required? If everything from the boxes back will need to be removed this might have to be a fall project.

According to Scott Smith at Formula the X Dimension on the 99 353 with boxes was 18 inches and 1/2 inch higher than non box boats. I measured my prop shaft height from bottom of hull directly in front of drive to the nose cone point and got 4.5 inches. Some people I've spoken to say this seemed too deep but they were not familiar with the 353 stepped bottom. Does anyone have their numbers handy for comparison? Thanks

I'm interested in what you come up with. I just picked up a 2000 353 with 500's / 30" Bravo 4 blades... Low water pickup 1.5 drives.
With just a quick run before layup it ran 79-80 at 5100rpm. 1/2 tank if fuel. Slip seems high. A friend asked me to check the depth of the drives and they seem pretty low. Gets on plane very well. Was on an 06 with 496HO's and it had a hard time with any tab involved. I played with shorties on my 42 a while back. Didn't carry the bow well. So if I did anything from here I would try 4 blade Hydromotives first. Or might be too much gear case too low and having a hard time pushing it through the water. I'm going to check drive alignment for the hell if it also. We'll see...

I spoke to some other people and 4 to 4.5 inch propshaft depth seems to be correct for this boat with boxes The 496 353s were a pricepoint offering imho and are fine cruisers but have a tough time getting across the high performance threshhold since its not a light hull. As for the props I think most people with good power are running labbed Bravo 30's or Maximus 5s but like to keep their little secrets. I heard formula used Hydromotives on their race boats back when they were campaigning but the right size Merc prop should be just as good since its mostly in the labbing.

Jersey is a hard spot for performance anything.... cars, trucks and especially boat propping! It is an expensive game trying yo tinker to get it just right. I know I have been paying shipping back and forth from the west coast to get my ol gal dialed in after the repower.

Where in Jersey do you boat?

Check out www.formulaownersofnewjersey.com for local happenings.

Brick / Barnegat bay area

Cool, that's where most of us do our boating. I hope you get your boat dialed in the way you want. It is an expensive ordeal lol.

https://scontent-lga3-1.xx.fbcdn.net...50407516_o.jpg

Thanks this is the truth. Maybe see you next season. Unless Santa brings me new silencer tips you will hear me before you see me. Lol.

My 1999 353 ran between 88-90 with a similar set up. Imco boxes (standard rise) -2 SportMaster shorties. 88 turning the props out and 90 turning in. Aggressive tune up with advanced timing and running lean. Safe set up was in the boat before I sold it and 86-88 all day. On the dyno, 700 corrected hp thru standard headers, with the CMI's on the dyno and running ALL accessories, a true 640 HP at the crank.

BBlades props 5 blade Mercury Maximus with the diffuser removed, started with 15 5/8" diameter cut down to a little over 15 1/4" 28 pitch everyday props. Mercury Racing 4 blade lab finished 30 pitch 15 1/4" tweaked by BBlades. Both sets, similar results on topend speed. Better cruising with the 5 blades and quicker in gear around the docks.

Engines were turning 5600-5800 RPMS Max, depending on the weather.

Lots of trial and error, lots of money spent to squeak out the last couple mph. The boat did run over 90 a couple of times with the right day. The bow will always feel low, but in reality, it is a sensory thing. Look over the side of the boat while you are running and reference where you see water on the hull sides. You might be surprised how far back that becomes while running at speed. Don't over trim based on what you think is right, take your time and let the boat settle before making trim changes, minor trim changes make pretty significant speed changes.

Good luck!
Dave

Thanks for the tips Dave. Did the shorties help much? I'm set at about 4.5" now - do you know what your propshaft depth was with the std lowers? You got me by 10 cr hp on the dyno with headers but I'm running Gils in the boat and still quite a bit off your mark. We did find out at the end of the season that one of my dominators was going bad so that was not helping. May try Quickfuels next year. Were you carb or efi?

https://www.youtube.com/watch?v=v1mli79565U Here's a video of the boat running this past May with the setup that Dave mentioned.....As you can see the acceleration is awesome.......by the end of the video we are running 85MPH

Carbs are Demon Marine. Shorties were good for 3-5 mph. i don't know what the finial dimension was, although I did try several spacers on the -2, it was best at -2. The boat was stock x dimentions before the boxes.

God luck,
Dave

I have a 312 with 625hp whippled motors. I am currently turning bravo 30p props on it, and on a good day, I can just bump the rev limiter. Sounds like 30p props are about as good as am I'm going to do. Don't think I have the horsepower to spin 32s.

Just a thought, how about Smitty at Wazzup Racing?

Dave

Offshore Performance right outside of Somers Point has a good reputation and their own dyno. Very nice guy named Bob runs it, very helpful.

So that spedo pic back then showing 100 was just a boner deal? Remember now, the truth will set you free!