WOT vs speed Sea Ray 280 Sundancer Also fuel level quesrion

Madifonzo

New Member
Sep 30, 2013
716
Boston, Ma
Boat Info
2005 280
Zodiac Zoom 310 9.9 Honda
Engines
Twin 5.0 MPI with Bravo III Drives
So I am constantly hearing reports from people on CSR and elsewhere that o should be able to get 50 MPH out of my boat.
I have twin 5.0's with bravo 3's. Bottom is clean tans are up.

Yesterday I had to make a fuel run. Tank had all but enough gas to get me to the dock...no gear, full water tank and just me in the boat. Water was smooth as can be...like glass really. So I decided to open her up. With drives fully tucked (if I add any trim, the props cavitate), throttles pinned I could only get 35 mph out of the boat at 4500 RPM. Specs for the engines states that WOT is in the neighborhood of 5000-5500 RPM. I am running stock Bravo props...24P if I recall. What gives?

Second quesrion is regarding fuel. Gauge will often show 15 gallons of from reality. Granted it's 15 gallons more than the gauge shows but still, that seems like a large margin of error.
 
So I am constantly hearing reports from people on CSR and elsewhere that o should be able to get 50 MPH out of my boat.
I have twin 5.0's with bravo 3's. Bottom is clean tans are up.

Yesterday I had to make a fuel run. Tank had all but enough gas to get me to the dock...no gear, full water tank and just me in the boat. Water was smooth as can be...like glass really. So I decided to open her up. With drives fully tucked (if I add any trim, the props cavitate), throttles pinned I could only get 35 mph out of the boat at 4500 RPM. Specs for the engines states that WOT is in the neighborhood of 5000-5500 RPM. I am running stock Bravo props...24P if I recall. What gives?

Second quesrion is regarding fuel. Gauge will often show 15 gallons of from reality. Granted it's 15 gallons more than the gauge shows but still, that seems like a large margin of error.

any canvas up that could catch wind?.....do you have a flag flying that could catch wind?.....any wind blowing?....props in good shape?....how old is the fuel?.....does the fuel have ethanol added?.....when was the last time the engine was tuned up?....flame arrester clean?....anything wrapped around the prop shafts?....

need to find out why the engines cannot reach the expected WOT range.....either the engines are not running well or something is creating too much drag on the hull or something is wrong with the props....

cliff
 
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I have the 4.3L's and I've seen 49.9mph on GPS. The bay was smooth and I was on a gas run like you. Holding and fresh water tanks were low, gas was low and only me with a few beers in a cooler. I could have gotten to 50 but didn't know how much gas I had left.
 
I noticed in your profile that you have a Zodiac dinghy.....I assume it was not on the boat when you made the WOT run.....

cliff
 
The best I ever got out of my 280DA was 48 mph at 5200 rpm. That was with brand new bottom paint, 50 degrees and the camper top on. I think the camper top actually decreased the drag. You should be getting at least 5000 rpm and 45 mph. Your speed at 4500 rpm is low. That you can't trim the drives at all is not normal. You should be able to trim to 1-1.5. I would check the props as Cliff suggested.

MY fuel gauge read like yours. 15-20 gallons at close to empty.
 
Agree with the comments about trimming up. You absolutely should be able to trim the drives up some. Maybe you're just trimming up too far, too fast?
 
My 280DA was not a 'set it and forget it' boat when it came to drive trim. At normal cruise speeds it took very little trim. The faster I went the more I could tweek up. I hit 49+ WOT sometimes but I had to adjust the trim in steps to get there.
 
Thanks for all the feed back and questions.
Bottom is clean and painted with ablative. Props are clean and there is little to no growth anywhere on the drives. Engines were tuned up past season with plugs and wires and rotor. While I don't always run Valvetec, the last fill up was valve tech 89 octane.

Oh, and I did not have the dingy on the back.


With thy respects to trim there seems to varying opinions on that. Many 280 owners on this site have reported that trimming up at all causes cavitation. There are several threads regarding the trim limit insert on Bravo drives...I think it's related in some way. That being said I can't see a 15 mph difference based on a slight trim difference.

I am am wondering if prop pitch is playing a role.
 
Well you have the right prop pitch. so what else is going on? You've also had this boat a while. Was it also that slow then ?
 
Yes...this has been performing the same way since I have owned it. I guess I'll have to play with trim. What I would be curious to know from other owners is what is your WOT speed with the drives fully tucked and no tabs. Maybe that would help to support the trim issue. Maybe the trim motor is trimming up to far causing the cavitation. I know I need new trim limit sensors which is a new issue.
 
Unless you're carrying a boatload :smt001 of extra gear, there's either something wrong with the engine/drivetrain or the hull isn't getting far enough out of the water. There really can't be any other explanation. I've run quite a few of these 280's and the speeds that the others are posting are spot on. There is no reason yours should be any different. The only other thing I can think of is a major hook, or something, in the hull... which would be EXTREMELY rare without MAJOR improper care or an accident/poor fix.
 
No extra gear...probably less than most. I'll have to try the trim. What kind of speed should the boat see with drives fully tucked. Is it a 15 mph difference fully tucked vs trimmed up slightly? What is a hook? I have never heard that term.
 
You know, I'm not sure I've ever paid attention to WOT with the drives fully tucked... or for that matter, I'm not sure I've ever done that! With many boats (planing style), too much speed with the drives tucked all the way will result in the hull listing (leaning) to one side. But, just "extrapolating" from experience, I would not be surprised if it wasn't AT LEAST 10MPH... and 15MPH sounds very plausible.

A "hook"... It's sort of a big dent in the hull, near the transom, that acts similar to the drives being tucked in or having the tabs deployed (down). I have NEVER seen this on a Sea Ray hull, but I have seen it on others where the trailer didn't support the hull well enough and over time the rear roller sort of "sunk into" the hull a little bit and caused that dent. I think having a hook is a long shot (and hopefully that's not the case), but it's about the only other thing I could think of that could explain it.
 
You won't get a 15 mph increase by adjusting the trim. 3-4 mph is more likely.
 
I own that boat he's talking about. There is no 10 or 15 mph to be gained by trimming. Like JimT says 4 mph is about it. It's a very bow heavy boat and I never even bother to trim it cause it's not a WOT kind of boat
 
Well, I'll defer to you guys since you have more recent experience on that hull than me. Plus, as I mentioned, I don't recall ever doing that with that boat. On some hulls, though, it is quite possible. I really would have thought it would be more than only 4mph, though. However, as you guys can attest to, with the V-8's (and even the V-6's) that boat can downright boogie when you get on the throttle. I don't know if you guys have ever done it, but you can even throw her into a hard, tight turn and she carves right around. It's still a relatively small boat so you can have some fun with it. Other than the wake size, it even makes for a pretty good boat for watersports.
 
Oh... I wanted to add something that I sort of glossed over, before. It was mentioned above, but is this speed based on the speedo or GPS? Speedo's can get partially clogged to where they will still function, but not always allow the needle to go as high as it should. Also, how sure are you on the 4,500RPM's (I just want to double check)? I don't have the book in front of me, but if memory serves, 5,000RPM's was the MAX for your model year engine. Also, double check your prop pitch. It's stamped right on the side, between the blades.
 
For the fuel issue... I don't get involved too much in the Smartcraft stuff, but I would look into doing a reset or recalibration for the fuel sending unit. Check the manual, or try to find one online.
 

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