2000 5.7L Bravo 3 Can’t Get On Plane

[Cmore260]

I have a 2000 sea ray sundancer 260 5.7L mercruiser with a bravo 3 outdrive. Starts right up every time and idles great. However, never can get up on plane. RPM will get to 4,000 WOT and speed is gps’d at 21. Most of what I’ve read online about this boat and power pack, should be able to get to upper 30’s no problem. Any idea what could be causing this?

props appear to be good, engine was just serviced 2 months ago. Hull was cleaned at that time as well.

 

[altitude 411]

20 year old boat that may be water logged... have you weighed the boat lately? That is a heavy boat at 6200 lbs dry, a full tank of gas @ 85 gal is another 500 #. Water on board 28 gal is another 230 # . Your almost 3 1/2 tons with nobody on board. Seems a lot for a small block. Compression and leak down test may be in order as well. Have you had the boat since new? How many hours on the engine?

 

[AKJohne]

4000 RPM is low, I am not familiar with B3's, However my boat is 6500 pounds and 5.7 A I GEN II and can cruise 24 to 28 MPH, will run high 30's at WOT ~ 4600 RPM. Props or engine is the issue. Have you had the boat for awhile? Did it use to get on plane with same prop... not much info to go on.

 

[hnt]

You should be turning 4600-4800 rpm at WOT. Have you ever turned that since you have owned the boat? What props do you have? Check your plug wires. I once bought a 25 Sea Ray with 5.7 that ran smooth as silk but only turned up about 4000. I found a plug wire off on each side.

 

[Scott Danforth]

are you dropping the drive all the way down for the holeshot?

 

[tank1949]

Lots of UKs!

 

[QBhoy]

Hi
could be a number of things here. Depending on how familiar you are with the working of a boat.

firstly, I’d be almost certain that at 21 mph gps, you are on the plane, all be it at the lower end of things. Especially at 4000 rpm.

you likely have trim tabs on that boat. Are you aware that once on the plane, if they are still both fully down, you will have some serious drag and drop in potential top speed. Your whole hull from the bow back will be dragging in the water.

as said already. Do you know how to trim your boat ? If I have my outdrive all the way down to plane...it’s ok...but once on the plane, you want a level or just more trim to be comfortable at cruise...but for top end performance, you need to be trimming the drive up a fair way to lift the hull out the water for less drag.

if it’s the case that you have the tabs right down and the drive right down...you’ll never see anything more than what you are getting now. Makes a huge difference, getting the trim of a boat right. Perhaps an extreme example, but it’s probably close to a 15+ mph difference on my boat. Not sure how much rpm difference, but it will be at least 500/600 or more.