porpoising-prop, ballast, or ???
 

I've got a 1990-91 Baja Bandit 223. It's beautiful and fast, but a shallow hull, so rough ride. But anyway, due to hull design oversights it's got a pretty significant porpoising issue, probably due to weight distribution. It's got a 454 mag, with a Bravo 1, both just slightly beyond stock. It's 25' long, 33" draft, 15 degree deadrise, about 3600#.

I started out with a standard Mirage 23p, and then tried a 23 plus, but didn't notice any changes in the boat. She'll do 70+ in the right conditions, but getting her there is difficult, as it goes into porpoise mode quite often. Seem to always have to drag the tabs, which prevents top speed of course. A little light on the fuel load seems to help a wee bit, but there is no way to "drive out of it" or past it for that matter, as I've driven it in every possible manner and trim configuration to prevent the onset of the porpoise.

So what's the next step? I guess I could try a 4 blade, but what size? What about configuring some sort of ballast system?

This boat looks and runs like a 4 year old boat, not a 20 year old boat, so I'm not ready to give up on her just yet.

Suggestions?
Thanks.

Sounds like you have a stern heavy hull with a decent amount of power. (BTW, I kind of doubt you're drafting 33" of water. Freeboard maybe?) The Mirage has a decent amount of bow lift. I'd suggest trying a prop with more stern lift - which most 4 blades have. One call to Brett a Bblades should give you more than enough correct information.

Thanks for the reply. Absolutely more stern lift, the mirage plus with more cupping was "supposed" to add some, but it did nothing. The 33" draft is a factory spec, bottom of the skeg maybe with a bunch of fat asses on board?

Now, what 4 blade should I shoot for? Buddy's got an Eliminator of the same size and relative power, and he's got a 28 4 blade. Granted, much better hull design, but has no trimming issues and doesn't appear to sacrifice any speed.

I did contact bblades last year and I think a got a "general" response. "Need more cupping" and "the 4 blade will slow you down". But I'll see when I can schedule a test period with a 4 blade with them.

I don't think you can spin a 28" 4 blade (very fast) you'll need a 22"-26". Have you checked the bottom to see if there is a Hook on the running surface? everything you described sounds like a hook.

The hull is like new, no hook. It's a design issue. That's why they added tabs at the factory after the first year of production. All of these hulls (produced by Sunsation) had the same problem. I agree, 28 sounds a little big, but I'm running close to 400hp essentially on a big ass bass boat (shallow hull). Once on plane, she takes off like a rocket ship, but I do sense a lot of slip and occassionally blow out on low speed turns and such. So 22-26" on a 4 blade, what should I try?

Thanks.

the 22" 4 blade is going to have rpm similar to the 23" 3 blade.

You should start with a stock 22" Bravo 1 4 blade.

Right. Hmm.............well, the 23 revs her up pretty good, that is, if I can handle the boat up to terminal velocity, but I think I've got a decent slip ratio in there as well. I guess if I try a 24 4 blade I can move up or down. Thanks to all for your input.............decisions, decisions, decisions........

Look to the bottom. I am fixing a velocity 22 that was impossible to drive

You'll need to clarify that a bit. that is "bottom of the boat" or "bottom number on props". It's not impossible to drive, it's just a game of chance whether or not she'll porpoise, and the research shows all of these hulls had the same issue. I can get her beyond 60, but not without dragging some tab, and in a windless and waveless condition, I shouldn't have to do that. But everyone's input here is going to finally resolve the issue, and maybe I'll sink her, maybe I won't.

I don't think Baja made a boat without some hook in it. My 280 is much better with 4 blades.

Right. To me Baja's are a bit on the low end of the cig boat spectrum, but then again Sunsation actually molded this hull, so who the hell do ya blame. There's no physically noticeable hook, but I guess if I took mic measurements, it wouldn't be perfect.

To four blade land I go, where it ends up, nobody knows.

:boat:

"you'll have to clarify that a bit"

physically noticeable as in with a long straight-edge? or just to your eye?

If you take a 4 foot long straight edge, I bet that you will find a hook. You might be able to overcome the bottom with a 4 or even a 5 blade prop, but if you do have a hook, the boat will be faster, more fuel efficient, and much easier to drive if your bottom is straight. It is much easier to fix a handling problem if your bottom is true and sharp.

Thanks for all the input. I'll try and prop my way out and see where it goes, I'm thinking a bit more stern lift via propping will help some. Thanks again.

DIAMETER? I think the mirage 23 plus is 14 5/8, so if I go down an inch in pitch, where should I go with my diameter? I've found 14, 14 5/8, 15 1/4 and others.

Thanks.

Bottom of boat. You may find the issue in the hull. props can make it worse too.

+1 on the bottom. If Sunsation built the hull, maybe they can help you. I think your speed is out running the hull. How does the boat ride at 50-55 MPH? If the answer is "good", get someone to help you with changes to the bottom.

Two suggestions based my experience with a similar boat.

First, find a boat shop at a marina that will let you water test props. The one I found required a credit card deposit and then let me test as many props as I wanted. So, I took a Tuesday off work and headed early to the lake so it was empty. I took the boat in and out of the water to change props. Take with you a stopwatch, gps and a notebook. Nothing better than simply trying different options. I also bought a prop from them. It was maybe $100 more expensive than I could have got it elsewhere, but being able to test 5 props in 1 day was well worth the premium.

Second, going from a 3b Mirage Plus to a 4b Revolution in the same pitch did wonders to tame down my boats porpoising. Whomever said a 4b Bravo 22 will run near same rpm as 3b Mirage is right. I found the 4b Bravo's diameter to be a bit overkill for a smaller boat. The 4b Revolution was spot on - improved holeshot, better cruising speed, much less porpoising and only a tiny reduction in top end vs the Mirage Plus.

So, test some options if you can. If that's not possible, go with a 4b Revolution 23p.

I would try a Rev4 as well. Lots of lift and bite. Propgods.com has a prop testing program that might work for you.

Okay, now it's Winter here and I have time to analyze this once again. I got a Ron Hill 4 blade 22 for Bravo I. As expected, quick to plane, stern lift, more stability, a little less on the porpoising issue (have determined: less fuel, less porpoise.)

Anyway, I can run about 70 with a 23 Mirage Plus 3 blade. With this particular 4 blade I get close to 60, and the engine's reved out. Now granted, I know I can push a bigger prop, but I'm wondering, could the stern lift be too much already? You can physically feel and see how much more the boat sits higher in the water when running on plane. I'm gonna sell the 22 soon, but wondering should I try a 24 or 26 next?

Thanks ya'll.

I would try a 24 Bravo prop. A 26 will be too much. Use a box stock prop so you can get a solid baseline and then maybe have BBlades custom lab it.

Do you have trim tabs on the boat?

If you do, try running them in a neutral position, even with the bottom of the boat, or just a hair under and see if it improves.

also, what position do you have the drive set? is it over-trimmed?

I had the same boat ( but with a 502) from 92'-97'

I never recalled it porpoising...... as mentioned, the ride sucked on anything over a ripple.

I ran a 24 turbo 3 blade on mine....tried a hydro Q4 once ,
didnt work so well.


I'd be looking at the bottom too...the drives on these are pretty deep, 3 blades should be the best performers.

Panther, If I drag some tab, it does help remedy the problem, but, of course, will sacrifice speed.

JT, my hull is stamped late 90, and they changed the hull dimensions the very next year (91 and up), not sure which year had. Mine is titled a 91 but is actually a 90. Yes, skips like a rock on a pond, but launches like a bullet!

Anyway, if anyone needs a test hours only 22p, let me know!!

[QUOTE=bigbang;3571576]Yes, skips like a rock on a pond, but launches like a bullet!QUOTE]

A friend of mine had one of those many years ago. Yes, it launched like a bullet, but it rode like a floor jack. We always used to bring Rick's boat up when we discussed deadrise and its effects on speed and ability to handle rough water. Yea, Rick had the speed - and a good Chiropractor! One swwet looking boat though!

Intentional hook in the hull will raise the stern and cause the boat to ride flatter with less porpoising. So, I doubt your boat has a hook. Boats with a rocker in them ride with more bow lift and tend to porpoise more as they can, well, rock back and forth. :D Add a prop that tries to carry the bow but can't and the porpoising gets worse.

Now unintentional hook in the wrong spot, only on one side, etc would give you some weird handling issues.

Just put a straight edge under the last 4' of the boat on each side and see what you have.

For a prop my vote is for a Rev4. Fast 4-blade with much better bow lift than a Bravo and much better handling than a Mirage +. Every boat is different but I went through the same thing. I was certain a stern lifting prop would help as the boat would ride flatter. Both the Bravo and Quad4 may my boat handle horribly.

As others have said try just barely dragging the tabs. My boat has a slight rocker and if I really hang my boat out all the way in calm water it porpoises. Dragging the tabs just slightly calms it down and scrubs very little speed(about 2mph). At cruise I HAVE to drag tab.

Just my point-o-two.

Mine was a 91'... 92' is when they went to 20* bottom....and they dont ride
much better.

bet its rocker, I have it and its bad on my saber boat wants to leap out of the water, going to take it out. its the last 4 to 6'' of the hull.

it sounds like the boat has some hook on the bottom,as allready mentioned,check the last 4 to5 feet with a straight edge,if you get the btm straight,you will see a world of difference in ride quality,there is a shop by me that does btm work every day.good luck.