Bravo 3 prop slipping

V

VernJ33

New Member
Aug 25, 2020
14
Boat Info
2007 240 Sundeck
Engines
305 Mercruiser MPI, Bravo 3 2.2 ratio, 22p
I have 2007 240 sundeck with a 305 MPI with bravo 3 2.2 gear ration with 22pitch props. I am have an issue with top speed. The boat has a great hole shot and can hold plane easily at 15 mph, but I am crusing at 3600 rpm at 25mph and i am maxing out at 4650 at 32mph. According the calcuatlors that's 27% slip. It seems like everyone eles with this setup is running the same rpm or more but faster. The props are clean with no dings, i have tried every trim position with no change. The boat has trim tabs from the factory with a smart craft thur hull transducer. There's nothing eles installed on the boat. I did paint the props with a prop paint and notice it immediately came off on the edges of the prop. Boat had same issue before the paint, also there is a piece missing off of the skeg 0527201601.jpg 0527201601a.jpg 0527201601b.jpg . Any thoughts? Thank you.
 
B3 props don't slip. Got the trim tabs up? Does the speed and rpm both increase proportionally?
 
Thanks i know the actual props can not slip because its a solid hub, but something is causing them to ventilate or cavitate. The trim tabs are up all the way, and yes if i leave the drive down all the way, i will get to about 4200rpm and then if i start to trim up the boat will "release" to about 4650.
 
No rpm and speed increase together.
 
Is the 32mph verified with gps? If so, this is very low.
How about some more Info?
How long have you owned it?
Is this a new issue? What is the top speed you used to see?
Tune up records?
Ever done a compression test?
Cool fuel 3 module paint issues?
By giving us as much info as possible, you’ll get to the cause much quicker.
 
Yes that is gps speed. I have owned the boat for two Years, it has always been an issue. I bought the boat with issues. Max rpm used to only be 3300. I replaced both heads due to burnt valves, compression is 160-165 on all 8 cylinders. Fuel pressure is steady at 43psi at all rpm. Brand new NGK ITR4A15, cap and rotor, wires, distributor is phrased in by using mercruiser service bulletin using led light. New crank sensor, Fuel filters(both of them) have been changed, injectors have been taken out and professionally clean. No paint issues,Total timing is 26*. Just replaced sea water pump, and manifold and risers. Bellows,gimbal bearing, shift cable have been changed, alignment is good. The boat is bottom painted but is clean. Engine serial number is 0w661357. The boat runs great, it just seems like the faster you go the higher the prop is "slipping" it seems like everyone eles with the same setup is crusing around 3200ish rpm at 25 and i am at 3700. Unless my tach is off but i have a diacom and it is matching the gauge.
 
It is wet slipped, but these numbers are from the the day in the water and is still current 3 months later.
 
Also the props are installed by "clocking" them.
 
That would prevent the engines performance no? The engine seems to have power, its the rprm/MPH ratio thats seems wrong
 
According to serial number its a 2.2
 
Try confirming rpm with a digital tach, boat gauge could be off.

serial number on engine or drive? Drive could have been replaced over the years.
 
Serial number from the drive. I am getting the same RPM from the gauge, and the tech mate scan tool.
 
Some possibilities:

the props were damaged and repaired to the point that the diameter is now reduced. Measure the clearance between The top of each prop and outdrive. See how that compares to others with the same props.

Do you have a strainer or anything else installed on the hull ahead of the drive? That can upset the water as the boat travels possibly creating cavitation.

Have you removed the fuel pressure regulator on the cool fuel 3 module (not the one on the fuel rail) and looked for paint debris?
 
There is no strainer on the boat, its still using the outdrive as the pickup. I have looked on the regulator on the actual module and it was clean and was also replaced. Thanks about the measuring of the props.
 
Is the serial number off the engines tag or the drive tag?
See if the drive itself still has the serial number tag and ratio tag?
Where are you located geographically?
And where did you buy the boat geographically speaking?
Because there is no 2007 240 prop chart I can find on the SeaRay.com site
But the 2006 alludes to and the 2008 lists a high altitude option 2.43 gearing
Which just about fits all those RPM/speed differences in a prop calculator I ran.
 
Serial number is from the engine tag which matches the original sales invoice from marine max and also called mercruiser and thats the same outdrive number in there system. I am located in New Jersey on the barnegat bay.Drive serial number is Ow922026. Thank you
 
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