I am carrying minimal equipment. Nothng in the water but drive and tabs. Actually the more I think about it, I'm requiring alot of left tab to offset torque. Almost 3/4 on the throw on the left tab of the 280 K planes. Could this be causing so much drag that it would reduce my RPM to 4650? Doesn't seem like it would. . .

Hey Kirk,

Where are you running the tabs on the indicators? Shouldnt need to be much past 5. If you are running much past 5 you are getting a lot of drag right there. The reason I didnt like the bravo props on that boat is the reason you are having to use add. port tab. Too much blade area for such a light and narrow beam boat. It manhandles the boat. I guess the diff. in salt to fresh is substantial. I actually like the hydromotive on that boat. It has plenty of natural bowrise, in salt anyway, to offset the nuetral lift of the hydros. Good luck.

Mark

Mark, I'm running close to 8 on the left tab!! I agree that the Bravo has too much blade area. Why would Jo and others be running them successfully, yet I cannot? Too much torque/HP compared to what they are running? This all makes sense though. What do you think about a 25 or 27 Hydro? oR should I get an assortment of Mirage Plus props?

Thanks,

Kirk

More torque = more tendency to want to lean wiht the narrow beam boats. It is hard for me to say not knowing the handling diff. between salt and fresh, but you should not need to run that much tab. Where is the right tab set when the left is at eight? Is it eight when at cruising speed and above? If so when you are up to speed have you tried bringing them up and see if the boat stays balanced? Remember how snotty the water was the day I took you and Joe out on the test? I showed you the tabs set at about 5.5 on the indicators.
Try the 25 hydro if you can borrow one. I have a 23 I used to run on that boat I couls send you but it might bump your rev limiter depending on where it is set. Mostly I ran the assorted mirage +s, but you have to get past them blowing out. It takes some practice but after a while I did not have a problem with that. If you wanted to stay with a bravo I always wondered about putting a shorty lower on the boat. I thought that it would take away from some of the torque effect if the props was not as deep in the water. Keep me posted.

Regards, Mark

5.75!!!wow...that's a big # for a 4 blade!...better look at bringing that up.

So none of the props you've tried would turn more than 4800?

If you're running with the tab down that's your problem. Too much drag!! Run with both tabs all the way up. If needed put a some weight, (sand Bag) in the stern (on the right side) to help level the boat. And any movable weight, anchor, lines, fenders, cooler. Good Luck.

"If you're running with the tab down that's your problem"....this is incorrect statement!...you need to find the ROOT CAUSE...then and only then correct that....not put band-aids on assumptions.

you need someone that can assess this thing as a system...look at the engine,,,the hull,,,drive,,,prop...

Joey,
I was answering Kirk's question, "why can't I spin the prop?". The answer is to much drag!! He is running with his tab down.
The items causing him to run with the tab down needs to be corrected. Wrong prop, CG off, drive too low etc.. The boat needs to be set up.

I agree that the boat need to be set up properly, but Mark , the previous owner had the boat handling fine with a 29P Mirage, as did I when I brought it home. I think he is correct about the torque on such a narrow beam. I'm looking to try a 25P or 27P Mirage plus this week and see what it does for me.

Nothing has changed since Mark owner the boat except for a little more HP/torque. The drive is the same and the boat balance is the same.

Maybe a shortie lower would help??

By the way - Thanks for everyones help. Especially Mark for always giving me valuable input, but you're not getting the boat back!!! Ha Ha Ha

If you have a Bravo drive then it might be advantagiuos to try a left hand rotation prop to counter the torque. This usually makes the boat require far less or minimal tab....which will lead to increased Rpm of course. Let me know if I can help you out!

Julie
Throttle Up Propellers
877-842-6855

Rotation
 

You would think that turning a left hand prop would counter the torque of the motor, but the boat is set up for right hand torque so it was really bad/hard to drive.

I'm going to upgrade to full hydraulic steering this fall and start trying Mirage Plus props. If they tend to blow out too much, maybe I'll get one cupped. That should help the blowing out right?

Rotation
 

You would think that turning a left hand prop would counter the torque of the motor, but the boat is set up for right hand torque so it was really bad/hard to drive.

I'm going to upgrade to full hydraulic steering this fall and start trying Mirage Plus props. If they tend to blow out too much, maybe I'll get one cupped. That should help the blowing out right?


What about my drive depth...5-3/4" from the bottom of hull to the center of the prop shaft? Is this too low?

Yes, you will probably experience some blow-out while trying to plane the boat off as you are coming out of the hole with a 3-bladed Mirage prop. Just feather the throttle(s) a bit----but once on plane they go pretty well when it comes to top end speed.

Hang in there Kirk----she'll come to ya! :)

pantera get the drive serial# and call Mercury they will tell you the year and ratio. # is 920 929 5000

Its a 1.5 ratio. I think the 4 blade is too much bite. I'm trying the Mirage Plus this weekend

Try the 29P Mirage Plus in an hour...I'll post the result if I can get it on plane without blowing out!!

Tried the 29P. Blows out at 3000 RPM like crazy. Once underway though, still had alot of Port tab and had to keep the drive trimmed full down to maintain any control. What is causing me to use so much tab and trim the drive full down?

Having the drive tucked all the way in may be part of your problem. As the boat hooks up and rolls over you should be trimming up untill you get to what ever speed you want to go.
If I dont trim up before the boat takes a set it leans to port hard and STAYS there till I back off completly.
What excatly do you mean by maintaining control?

Dan

Dan has some good advice for you. I have experienced exactly what Dan is saying.
I rarely run my tabs lower than neutral, until the water gets rough. I don't have indicators so I normally start with them all the way up.
Try pulling your tabs at neutral, bring her up to 40 or so. Trim the drive until she feels right, then put the hammer down.
My boat does not have the kind of power you have but she handles about the same. These narrow boats also need a balanced load when you go fast. Do your testing with two people, you and one other.
You'll get it figured out.

Thats the same advice the previous owner gave me. I'll try it next time out...just seems too simple!!!

I'll let you know, I can't let this get the better of me, we love this boat!!

Rebuilt the heads - No Change
 

Took the boat out yesterday no change, can't turn more than 4800 RPM with a 28P Bravo prop??

Dan's correct
 

Pantera,I remember talking with you and now that I have really studied this thread over the past few months and it brings me back to my 2nd boat 24' very tall and thin hull design, it was a 24 offshore cobra:rolleyes: But had the same problem with Balance of the boat, also the way Pat MCP describes the trimming and speeds how to over come the boat roll and instabilility. it's the boat hull design or was in my case. but the drives need to be tucked on take off as well as both tabs nail the throttles down and start trimming BOTH TABS,AND DRIVES AT THE SAME TIME, UNTILyou reach some blowout of the props and then slowly ninch the drives down a touch, then equal out your tabs very slowly to correct a minimal amount, but at this time if the props are right you should be running on the pad evenly.JT 500's do you remember this, I know you do. I WILL BE GLAD TO WORK THE 28'S BRAVO ONES , JUST because I WANT TO TRY AND HELP. YES SOME MIRAGE PROPS 27 LABBED AND CLIPPED AND CUPPED, WOULD RUN THE FASTER OF THE TWO AND WILL HOLD ON TAKE OFF, AFTER WE ARE DONE. You know the 3-blade will run faster, but the 4- blades will help handling and acceleration, from 30 to 50 will set you back in your seat hard. Call me, if you want and lets talk again. Also you need indicators on your tabs would help.I know that the 4-blades will run up to 5,200 and with a increase of speed, how much I don't know.

Darin -

Thanks for you reply. I was blaming the prop initially until I lost (3) pushrod guides which caused (3) rockers to come off of the valves, so I thought I had another problem. The valve train issue has been fixed, I installed full hydraulic steering, which has eliminated most of the rolling, but I still cannot turn the 28P Bravo prop more than 4800 RPM.

I have several friends with Procharged stock 454 engines that are spinning 30P Bravos with no problem.

What else could be limiting my RPM? The engine ran grreat on the dyno, but it seems to be lacking HP in the boat. The only difference between the dyno and the boat is the exhaust. Whch may drop the HP 5 - 10. Even if it were more, I'm still over 600 HP.

rpm
 

what do you want to be at for w.o.t. rpm?,providing everything else is right.

Tried a 25P Spinelli
 

A friend let me try a 25P Spinelli, great hole shot and actually bumped the rev limiter at 5400 RPM!! Didn't think this engine could get over 5000!!

Darin,

I'd like to get 5300 WOT. I'm trying a 27P Mirage Plus this week. Will let you know. i haven't forgotten about you, just had motor problems. Now I'm back at trying to dial in a prop. Also added steering which is reall messy if you dont have a locking cap and reservoir!!

dialing in/ getting close
 

Kirk,You are getting close.

get some good numbers when testing, then we can get the prop dialed in on the money for you.
Thanks again for your reply
Darin.

Motors repaired, boat is put away for the winter...I had enough. I will try in April, if I can't sort it out by May 1 its going down to Pantera to try and be fixed!! If no luck then, i'm buying a new boat!!

Panter 24-650
 

I say thumbs up to you,I am sure ILL. I s getting a bit nippy:D heck it's cold here,anyway you worked your tail off on the boat, and next year -will be a good year either way you go.

repaired or new >YOU ONLY LIVE ONCE.:D

( I think):crazy: ;) talk to you later, Darin

don't forget we will be LABBING SNOW SHOVEL'S AGAIN THIS YEAR .:D (do you remember the big snow storm,everyone was showing off there HOT ROD SNOWBLOWERS.:D

hey Darin you still have the lab special going on for prop work?

What is the exact difference between the motor last year, and this year?

how did you dial in the CAM? did you advance, retard, or set the cam straight up? What cam did you use, and was it different from last year?

did you run a bigger cam thinking you would get more HP. I found out that HP numbers don't mean to much in a boat, the Torgue number and torque curve means more.

what is total advance on timing? What size carb? This is just a short list of the things that make the whole setup work properly.

Here is a quick story for you. I have a good friend who built a set of 540's and put it into a 37' outerlimits. I believe he pulled 600hp and over 600lbs. of torque on the dyno. The boat wouldn't go faster than 74 mph at 5000 rpms. I kept telling him, I think you have the wrong cam, I think you have the wrong cam, its too big. He fixed the problem by blowing a motor and putting in brand new HP 500's and the boat is running 80mph and bumping on the rev limiters. Same drive and prop setup, less hp and less tq. The cam chosen for the 540' was abviously the wrong one.

I almost forgot. He built those engines and put them into a smaller boat before they were put into the OL. The motors would never turn over 5000rpm in that boat either. He just assumed that because the drive height was so low this was causing the problem. he would put on a 23 mirage=5000rpm; a 25 mirage=5000 rpm etc, etc. so now it was the OL's turn and the results were the same. The problem was the motors all along. From the dyno results, these motors should have been turning up 5600 rpms. The torque curve was wrong.

60 props at $100.00
 

Mark if I COULD GET 60 LAB JOB'S OR ORDERS WITHININ 2 WKS I would do them for a 100.00 each:eek: :D
I WISHED:D ;)


ANYWAY ,YES GIVE ME A CALL AND I will hook you up on a great price.;)

Great questions and info Panther.

No difference in the motor. I lost a main bearing which took out the crank and the block. I reused the pistons, rods, cam, and rebuilt the heads - new valves, springs and keepers.

As far as the cam, its installed at 110 degrees intake centerline. 30 degrees total timing. The cam is the same one that was in the engine, it was in like new condition. It is a Crane HR-214/325. Very close to a stock 454 Mag Cam.

The engine is fuel injected with cleaned and flowed injectors, new fule regulator, pump and filter, all Aeromotive, proven parts as they are run by 4-5 local guys on with the same motors.

I posted my torque and HP numbers on this thread previously.

I appreciate your info and interest. Like Darrin stated, I've been busting my ass on this problem all summer. Hopefully I'll get it straightened out in the spring!!

Any other info is greatly appreciated. The more input I get, the more I check things all this will help narrow the problem down!!

Thank you,

Kirk AKA . . . Pantera24-???HP

any othe ideas?

You need to try a 26p Bravo. You will see a great improvement in rpm and all around performance. If that does work have Darin add a light cup and lab the 26. Or another option would be to have the 28p clipped and labbed. Darin will not let you down. He got me 4mph and 300rpm.

After rereading this again, you used a 29" mirage- what rpm and mph at wot? and same for the 25" spinelli- what mph at 5400rpm.

Again think about the boat as a moving dyno- the prop is the equivalant to the water brake of the dyno. The hull has it's own TQ requirement to move it thru the water. In your case it requires 700ftlb TQ to move it 78mph. Don't be surprised if the 26" bravo will not even go 78 but will turn 5050rpm because at that rpm you have 660TQ and your boat requires 700TQ to go 78.

How do we change/improve this? Less drag or more TQ. one of the few ways is to try a shorter lower unit. The other is more TQ like with a blower.

That 4 blade has alot of bite 5% slip and is probably the cause of the listing to port at speed.

I have an idea. With your low drive why not try a blackhawk drive, it will bolt onto your gimble.

Quick Question. Is the motor blown or naturally aspirated? If the motor is NA your full advance is way off.

I usually run 36 degrees total advance. I have even seen good results running race fuel and 38 degrees on the dyno but pulled it back to 36 for safety.. Anyway, if the motor is blown than 30-32 degrees is fine.

Procharger 5 PSI Boost