Prop slipping?
 

2006 Sunsation 288
525 EFI
bravo XR drive
ITS transom assembly
bravo 1 15.25 28 pitch brand new

Hello, just bought boat. Was told boat went 80mph. First time out boat maxed at 67 with 1/4 tank and 1 person at 5100rpm. As soon as the boat comes up on plane the rpm’s come up at least 1500 like it breaks loose. Was told prop was worn out. Ordered new prop exact replacement. Boat now does 72 with a full tank and 3 people. But the prop still slips a lot as soon as the boats gets on plane. Any thoughts on what’s causing this? It also cruises at 40mph at 3500rpm. Does that sound normal? Thanks

It is a bravo 1 FS 28 prop and I have all the plugs installed. The original was a reg bravo 1.

Yeah, you're slipping terribly...something like 35% at 40 mph and 21% at 72. This setup have a prop hub or is it solid? If hubbed, did you replace it when you did the new prop?

80 at 5100 ia only 11% slip, which would be very reasonable. Objective evidence indicates something changed from old owner's 80 mph boat to your 72 mph boat. Look to see what that could be. Obviously driver is one factor. Weight and balance could be another. Gotta ask if you are trimming the outdrive correctly?

it is a solid hub. I bought a new solid hub with the new prop but i reused the old one and had a shop inspect it and they told me it was fine. Kept a the new one as a spare.

I agree and I’m trying to figure out what. Maybe it’s not the same prop and he kept the good prop and gave me a **** one he had laying around. I didn’t mind buying a new one just to have a baseline to give accurate rpm information to a prop shop. But my main goal is to determine if it’s a prop issue or something else slipping. No rubber smell from engine and hub on back of motor was done last year.

im new to boating but I have an experienced friend who gave me some good advice and I also had him take it out to rule out operator error and the performance did not change. He told me something is wrong and it’s def slipping.

I'm not convinced that boat will run 80. Did you ride in it with the previous owner? That aside, maybe you should try a Bravo 1 30p or a 5 blade 30p. Bblades has a prop testing program.

I just did a quick search 525efi Sunsation 288 speed and got lots of prop and speed threads. Looks like 80 is very high end of possibilities but many ran not far from there. Many 76-78’s.

A 26/27 Daytona runs low 80s with that power. I would think about 74-5 mph is about right for this boat. I would still try a different prop.

Many of the props used where regular Bravo 28p. I don’t believe any of the boats i saw in quick search had the ITS.

yea I noticed the same and which is why I am concerned something else is wrong. It should do close to 80. I’m going to play with the new prop on more today but what concerns me more is how it just unloads and slips as soon as it gets on plane. Maybe that’s normal for these boats? I have little experience but I’m told by friends it’s not right. I like going fast but also don’t wanna piss away fuel while cruising.

You are using a FS Bravo prop though right ? So that and the ITS are different from the other boats.

yes, I have all the plugs in also.

Get a stock 28 Bravo to test. Get that out of the equation.

there was a stock bravo originally on the boat. I assumed they were the same minus the holes. Boat did same thing. The FS was all that was available without a long wait. With the FS my top speed is a little better but still slips as soon as it gets on plane. I’m ok ordering a custom prop. I just wanted to order this prop to try to figure out if I had another problem going on other than a prop issue. I’ve read the drive shower can cause cause cavitation at lower speeds. 🤷‍♂️

No way that boat will run 80 with a 525. 72mph is about right. It took 700hp+ for my 28 to run 80.

if that’s the case I’m still ok with it. I feel it has more than 72 in it. Based on the slipping. But my main concern is that there are no major issues that I can adresss over the winter and get it over with. I bought the boat from a performance shop on consignment. Owner always serviced the boat and did the motor work. He claims he personally saw the boat go 80. Weather that’s close to 80 or exactly 80 🤷‍♂️. I’m bringing it back to him next week. He has been away and I’d like outside opinions to make sure I’m getting accurate information. I know cars and engines but boats are new to me.

A higher pitch prop, 30, may help with your slip issue and speed, especially a 5 blade. My Daytona planes faster, has less slip, lower rpm at cruise and similar or faster top end with a Max5 or Maximus. If you want a lot faster on your Sunsation, look into installing a Whipple. It's only money. :)

Don't get too excited about high prop slip numbers. Nearly every single engine boat I have owned ran about 20% and when I would add drive spacers or blades to the prop to lower slip #s, bad things usually happened. An XR drive is the equivalent of a GM 10 bolt rear end, you hook it up too hard and it will break.

@Dagwell: you're saying after your boat planes, then rpms go up about 1,500. I think you mean ventilates, not slips. I believe slip is the difference between the theoretical forward thrust vs. the actual thrust. Ventilation is when the prop is pulling in air, not effectively biting. If your prop is spinning up or ventilating during / after planing, that indicates a pitch that is too small, you're running a shorty or you're trimming too soon. Again, I would try a 5 blade to help with that issue. Is your lower a Bravo or a shorter Sport?

Did you have a sunsation 288 ?

Comparing the standard Bravo I with the pro-finished Bravo I FS.

https://e-ribbing.com/en/propellers/...ravo-1-fs.html“As shown by its name, the pro finished Bravo I FS (Four Stroke) propeller is designed specifically for high-horsepower four-stroke outboard engines and is positioned somewhere between the standard and the lab finished Bravo I.

In other words, Bravo I FS is a new version of the standard Bravo I propeller in which some specific modifications of its characteristics have been made. The most important of these are the following:

• its exhaust barrel has been shortened
• the cup height of its blades has been reduced
• the leading edges of its blades has been become thinner and sharper

”

As you can see, They are not the same. All the owners with the 288 525efi combo that reported 75-78 had 28” Bravo props. Not the FS version. These where before the FS became available.

Beg, borrow, or steel a untouched Bravo 28” in good condition. Friends/fellow boaters/marinas or prop shops with prop loaner programs

Who said this?
Are you trimming the drive down to get on plane then up once at speed?

If your tach flares up super quickly then I'd say it's slipping, but it's natural for a boat once on plane to increase rpm if you hold the same throttle position as the load on the engine decreases.

If this is the case why didn't you just wait on him and have him do a ride along with you on board to school you on the mannerism's of the boat before buying a new prop?

Cavitation damage, strike rocks or whatever so it's bent to hell, cracks from surfacing maybe, run 2 hours in sand (lol) maybe where it's abraded away.

If none of the above, which I call damaged.
I'd like to see what a "worn out" stainless prop looks like.

You are correct in that the drive shower can cause ventilation and / or additional slippage if it is in the wrong place. Remove it and try it without, just to rule that out. If the boat has a pitot tube or transducer mounted too close to the prop, that can also cause additional slippage, especially on lighter smaller boats. The Bravo FS has more differences than just the ventilation ports. The diffuser at the back is almost totally removed compared to the standard Bravo prop. That is supposed to give more bow lift, and less stern lift than a standard Bravo. It is also supposed to reduce the drag a bit, improving top speed slightly. I have 24 ft Checkmate with a 300R outboard, so totally different. However, I tried a standard 26P Bravo and a 24P Bravo FS. The 26 was a bit too much pitch, but what surprised me was the 26 Bravo came on the plane much faster than the 24 Bravo FS, it lifted the back of the boat more and the bow less, and almost eliminated all the chine walking, but it was 2 mph slower. The Bravo FS is also "Pro Finished" which means more accurate cup heights from blade to blade and better balance (supposedly).
The even pitch Bravo FS has less cup than the standard Bravo if I understood correctly. They make the Bravo FS in 1/2" pitch increments. So you can purchase a 26P Bravo FS, which has less cup than a 26P Bravo. If you buy a 26.5P FS, they just add cup to the 26P. If you buy a 27P Bravo FS, they add more cup to the 26P, and if you buy a 27.5P Bravo FS it has even more cup added to the 26P. Once you get to a 28P it has less cup again. More cup typically reduces slippage. For fast outboards they say that the 27P would be good but the 27.5P has almost too much cup making it more difficult to turn. Depending on your rpm, perhaps a 27P or even a 27.5P might reduce the slippage if you stay with the FS family??
I would try to get my hands on a

it is a standard bravo lower. I have the drive all the way in before coming on plane. Then trim after at speed. Comes up on plane at about 20mph. And rpm is around 2k easing into it. One on plane I can feel the forward momentum die out and only way to fix is to give more throttle and rpm and then it slowly gains speed and the prop catches up I guess you would say. I def wanna try a 5 blade. I didn’t wanna wait 2 weeks for him to come back from vacation because I was worried something major was wrong with the boat not just the prop. $1000.00 didn’t bother me to kinda rule something out. In in NJ so my boating time is limited here to get this fixed for next year. Looks like I’ll have a almost new bravo 1 FS 28 for sale soon 😬

Ok. A shorty can create problems you describe. I wonder if you're not giving it enough throttle. I would firmly bring it up to 3,000 rpm (not full throttle not easing into it), let it plane, then keep rpm and slowly trim. If you haven't, try this before a prop. I don't think there's anything mechanically wrong. Also, a short hub prop will provide less stern lift. That can mean slower planing and possibly letting the prop lose bite, especially if you have through prop exhaust.

Thanks, ill give it a try. Trim tabs down or neutral?

You are correct in that the drive shower can cause ventilation and / or additional slippage if it is in the wrong place. Remove it and try it without, just to rule that out. If the boat has a pitot tube or transducer mounted too close to the prop, that can also cause additional slippage, especially on lighter smaller boats. The Bravo FS has more differences than just the ventilation ports. The diffuser at the back is almost totally removed compared to the standard Bravo prop. That is supposed to give more bow lift, and less stern lift than a standard Bravo. It is also supposed to reduce the drag a bit, improving top speed slightly. I have 24 ft Checkmate with a 300R outboard, so totally different. However, I tried a standard 26P Bravo and a 24P Bravo FS. The 26 was a bit too much pitch, but what surprised me was the 26 Bravo came on the plane much faster than the 24 Bravo FS, it lifted the back of the boat more and the bow less, and almost eliminated all the chine walking, but it was 2 mph slower. The Bravo FS is also "Pro Finished" which means more accurate cup heights from blade to blade and better balance (supposedly).
The even pitch Bravo FS has less cup than the standard Bravo if I understood correctly. They make the Bravo FS in 1/2" pitch increments. So you can purchase a 26P Bravo FS, which has less cup than a 26P Bravo. If you buy a 26.5P FS, they just add cup to the 26P. If you buy a 27P Bravo FS, they add more cup to the 26P, and if you buy a 27.5P Bravo FS it has even more cup added to the 26P. Once you get to a 28P it has less cup again. More cup typically reduces slippage. For fast outboards they say that the 27P would be good but the 27.5P has almost too much cup making it more difficult to turn. Depending on your rpm, perhaps a 27P or even a 27.5P might reduce the slippage if you stay with the FS family??

All the way down for faster planing. Depending on the boat, I bring the tabs all the way up once it planes and then the drive. I didn't use tabs while running, just one tab if there was a cross wind.

so, just got back from a test run. 3k rpm was the ticket. Comes up on plane super nice now. Thank you for the help. I still want to try out a 5 blade and maybe get my cruising rpm down a little. Save a little gas 😂

i just ordered a 5 blade mercury max 30. Found used in great shape low balled a guy for $750 and he took it. Good for a test at least. If my 525 won’t spin it might have to add that whipple 😂.

Doh ! Hope it works out better for you than her.

https://cimg9.ibsrv.net/gimg/www.off...84507d9375.gif

well, she is blonde.OP if your spinning a 28 4 blade 5100 you'll be hard pressed to spin that 5 blade.jmo.and they will break drives

Awesome. Glad that helped you. Save gas?? Then you're in the wrong sport! 😂 Did you try to open it up too? Tell you what, if that Max 30 doesn't work, I'll buy it for $750. Just LMK.

Did the dart board reference go unnoticed ?

https://cimg5.ibsrv.net/gimg/www.off...0162d33c3.jpeg

maybe not understood 🤷‍♂️

Am I missing something? RPMs are going to come up when a boat comes up on plane! Once it is up on top there is less boat in the water, less resistance, less load and rpms rise. Also when figuring slip remember a Bravo 28 is closer to a 27.

Padraig

Throwing darts can be painful.