353 Formula guys - need info
 

Looking for some info about what kind of speeds and RPM you're getting with what props at WOT.

I've got 502s with 28P Merc Bravo and she's running in the 4,700-4,800 range and not making it to 70 MPH on the GPS, does that sound right.

Thanks for the help and info.

Is it even on plane at this speed...Just Kidding. Seems a little off, the 496 boats are 72 to 74, I would assume the 502 would be very close, but I have no real knowledge on this hull/power. Maybe dropping down to a 26 to get the rpm up to get the last push will get you across the 70 mark. Are your props the labbed finished version or standard. Do they have a real shinny finish or somewhat brushed finish?

They're standard props (not labbed), good shape, brushed finished, not shiniy, but keep in mind they've been in salt the last several months,it's on a lift down here, but it's going back to LOTO here real soon, I was wondering what the max RPM should be.

I would be looking for 51 to 5200.

I don't know if the boat should hit 70 or not. I assume you recently bought the boat or you wouldn't be asking this question....so I have a thought:

My old 382 was fastest with 30P Bravos and would spin 5,600-5,700 (custom built motors). However, I wanted better cruise speed so I ran 32P Bravos for a 3-5 mph faster cruise speed. Those props would only spin about 5,200-5,300 WOT and the boat was 3-4 mph slower. It's possible the previous owner made the same decision I did and went with 28's vs 26's????

No, actually have owned the boat for over ten years, I've never been dissatisfied with the way she's run (top speed) or handled, I've never been a big speed demon, it's been a perfect boat, I've just never tried any other props on her and wondered what the top RPM should be on the 502s

I have a 2000 353 with 454 hp500 cam and heads last year. Basically 502, I ran 28 pitch props and got 75mph at 4800-4900 on gps on the best day. I have the same engines with b&m 250 blowers 5lbs of boost 608hp. I just hit 83mph at 5100 with a little bit more to go. Same 28 pitch props as last year. The cooler weather coming will help you out also.

if it responds anything like my 496 HO's, swap the 28's (too big IMHO) for a pair of stock 26 Bravos and loose nothing, but gain lower min. planing speed, midrange acceleration, and bring the RPM up and most likely break 70 with your 502's.

!00% proven win/win in my application.

This is your first choice Jim. My single 502 (509) spins a stock 24 Bravo solid at 65. Two 502's should get you past 70. If I lose the drive shower I'm normally 68 - 69. Although I did buy a 26 to try, just too damn lazy to change it out!!

Hmm..would like to know what would happend if I would put 26" to my 271 with 496 mag ho?

I just didn't want to get the RPMs up to high, maybe I'll see if BBlades has a pair of 26s to see what happens.

Thats what your rev limiter is for. If an engine will turn up to its rated RPM at full load it is working less than when barely making minimum recommend rpm range of mfg. Loading the engine more results in less rpms and the engine is under more load, being able to turn right at max rpm will ensure longer life when using the engine in the recommended cruising range.

I have a friend that had a 2001 353 at LOTO with 496HO's that ran around 72 new. He had 30P on his, which we always meant to swap my 28Ps on just to see if it was slightly over propped. But we never got around to it. Your speed is about right for that HP, age on hull and engines, etc. I bet BBlades could tell you exactly what trying the 26s will do before even testing.

I know and understand about the RL, but didn't know what they were set at on my 502s, I guess I need to try some diff props and see when they hit it.

I'll give Brett a call and talk to him about what he thinks will happen when I go one size smaller, he should have good idea what's up.


Thanks for all the comments guys.

I'd wait to prop test at LOTO vs Cape Coral if the boat is heading back to MO. You'll want to prop it to where you can turn 5K RPM at WOT on a typical boating day for you in terms of weather, fuel load, passenger load, gear, etc. That way you aren't dropping too many RPM on the worst possible days and not gaining too many RPM on perfect days. Rev limiter should be 5150 RPM on your motors and you don't want to be banging it hard optimum days. If top end is not that important to you I'd stick with standard (non-lab) finished props.

you could probably outrun that thing on foot in acceleration, and had to have taken f o r e v e r to reach that 72.
what RPM?

They are slightly overpropped with the 28's Formula specs with and tested on the 353/425 HP combo
I have the Formula test reports here from 2001, have lived with one, and stand by my experience 100%

Funny thing is my boat runs the same top speed on out of the box 26" Bravos
On my tachs 5000~5050 with typical boating weight.
but will leave that boat you speak of absolutely behind in a roll-on.

test report to my recollection was empty gear, empty water, two guys 3/8 fuel I believe two-way ave 72 at ~4800 with 28's.
OVERPROPPED for the real world, real weight boater with those engines...

LOL. You are spot on. It was horrible out of the hole. Can't remember what total RPM he ran at WOT. At the time I had labbed 28s I was running on a 454EFI 32 Sunsation. He so wanted to try those props since getting on plane sucked. Problem was neither of us had trailers, both boats were on lifts at LOTO. And every time we discussed a swap we had been floating in the water drinking beer. Bad idea!. When we ran together I would be a half mile ahead of him within about 30-40 seconds just do to hole shot. He originally ordered the boat with 502s but that was when they changed over. He got the first 353 with HOs in it, for the same price as the 502s. So he was happy. Not sure how long Formula kept shipping them with 30P props.

I am happy with the boat with the way it runs now, I was just wondering if I was leaving a few MPHs in the engines, but I don't want it to take a mile to get on plane and up to speed with any weight in her, I guess trying the 26s will tell me pretty quickly if I should just leave the boat alone or not, should be interesting.

Good luck Jim. When's the boat going back to loto? Still gonna sell it or keeping it at a place up there?

We took it off the market months ago, the boat is perfect and I couldn't let it go just because we wanted a CC for down here, we were thinking about just hauling a CC back and forth but decided to keep the Formula, probably do the two boat thing instead, we should have a place back there before the end of the year, then we'll have it hauled back after we get the new LOTO place squared away.
We'll start snowbirding next Summer, as much as we love it down here, we miss LOTO in the Summer, 6 months here, 6 months LOTO.



Thanks for all the help guys.

try some 28's labbed by Merc ....

I've got 28s, but they're not labbed, I think I need to turn some higher RPMs.

That's what the lab will do, gain the 3-400 that you need ... You could try the 26's but I'm afraid you will loose too much lower end ....m

Yea, I can't afford to do that, when the boats loaded it's hard enough to get her up, out and moving, as I'm sure you know the 353 is one heavy boat, just trying to max my speed with what she has since she's only turning 4,700-4,800 RPMs

When I went to the 353 from the 311 I was really concerned with the difference in planing time ... But after getting used to it....no big deal now .... It will pop right up ... And I'm turning 32's ....

What?

and there's no guarantee that labbed 28's won't slip more down low as in putting the boat on plane

for the cost of a lab job you can pick up a pair of 26's and go from there. If yur a happy guy peddle the 28's

quite frankly the 28's aren't working for you anywhere except at mid range cruise.

Speed .....low and mid .... Actually prob will plane better ...but as stated you have to try it .... They are ALL different ...m

I think it's probably the easiest and cheapest to try a set of 26s first, then go from there.

^^^Do this^^^

I wish i could double like this.

Put 26's on it and don't look back.

I will say this in closing...

you may not be leaving any top speed on the table, as in 26's may not gain you any MPH (as noted mine ran the same TS GPS 26/28), but for a little mid-range fuel economy vs speed you are leaving a lot of drivability and enjoyment.

again, my experience

Have fun.