2002 340 6.2L’s 16mph max

speakrdude

speakrdude

Well-Known Member
Feb 21, 2009
1,214
Northwest Arkansas
Boat Info
2002 Sea Ray 340 DA
Raymarine C80 Tri Data
Engines
twin 6.2 MX MPI
Weird issue. Every since I’ve owned this boat.
Clean bottom, lake water. Unknown prop size.
Factory trim tabs. (Ordered new Bennet add ons)
With both engines at 4k, Max speed 16mph (on my phone) built in Raymarine speed way low. Mostly plows, Not much on plane.
WOT is 4500. Both fuel tanks full. 2 adults. Full fresh water. Empty holding tank.

Purchased Rinda scan tool. says everything is fine, no code history. 700 hits each engine. Someone suggested pulling the props and have scanned for size.

Anything else? Injector cleaning? Would scan tool show dirty injectors? New cap, rotor on the port engine. Cleaned flame arrestors.

F089A815-2062-448E-93AF-A86CD72B9929.jpeg
 
Is it an I/O or v-Drive? If its an I/O, are you sure that your drives are trimming in properly to get on plane? If its v_drives that seems really strange. When you say WOT is 4500, is that where you are at 16mph? Should be more like 5000 to 5400. It seems like it may have the wrong props? WOT for the 6.2s should be a lot higher than 4500. Maybe the prior owner hit something and installed the props for the 8.1 version?
 
Have same setup 6.2MPI V drives and run 20MPH at 4K RPM.
 
That's crazy slow. But handles good around the dock right? LOL.

Have you calculated the prop slip on that? What pitch prop and what transmission ratio?
 
GuyFM said:
Have same setup 6.2MPI V drives and run 20MPH at 4K RPM.
Click to expand...

20mph or 20kts? Either way, that still seems way slow. I would not expect these results to be indicative of normal performance for the 6.2L.

To the OP - sounds a lot like props to me. Also sounds like a prior owner pulled a fast one on you, unfortunately. Bent some props, found a cheap set not intended for the boat, sold without a sea trial. The trifecta :)
 
Very possible.
8mph at 1800 rpms. How does that compare with others of the same ?
 
I'm running over 30 MPH at 4000 RPMs with 7.4s.... I thought you had this boat for some time... Is this a new problem? The props should not magically change. seems to me you might have you anchor down our something wrapped around you your rudders or prop... Since both engines are running the same RPMs I am not sure if is a transmission problem.
 
Only had this boat for four years now. Have had a few others, with 7.4’s before this one.
This boat has 6.2’s. It has run like this since day 1. However, I just realized that full of fuel, that’s an extra 2000 pounds, plus full of water, more tools and personal stuff, she’s pretty heavy!
 
I have the exact same boat and year with a generator.
The original props are 17 x 19 with medium cup.
My boat full of fuel water and 4 to 5 people will run 4800 to 4900 RPM at 36MPH.
3400 to 3600 is typically around 25 MPH
3200 is right around 20 MPH
3000 is about 17 to 18MPH.
Those motors cruise really nice and are happy around 3400 to 3600.
I have fuel meters and burn 30GPH combined at 3600 RPM
........................................25GPH at 3200 RPM
If the motors are running well its sound like you got a prop issue..
 
speakrdude said:
You have 6.2’s and vdrives?
Click to expand...
Yes.
340 Sundancer 2002
6.2 Mercruiser with ZF V Drives - 2.5:1 Ratio, Props 17 x 19 med cup.
Garmin Nav, Radar and Autopilot
 
Last edited:
People have posted that the 6.2s have similar performance to the 7.4s. For reference my 97 330 (same hull as the 2002 340) runs right at 30mph at 3400 rpm and is “singing along” in its sweet spot. 3000 rpm is about 25mph. At 20mph it is right about to fall of plane and is not efficient at all for a planing hull. I still think you have an issue with the props. Its possible that the 6.2s are very different from 7.4s though so may not be comparable at all. I know the RPMs to get the same speed is different.
 
Regardless of the power, Same hull, rpm's, gear ratio and the same props should give you the same speed.
 
scoflaw said:
Regardless of the power, Same hull, rpm's, gear ratio and the same props should give you the same speed.
Click to expand...
I think the gear ratio is different between the 7.4s and the 6.2s given the different power bands or maybe its the prop pitch that Sea Ray altered to match the higher rpm power band. But maybe not.
 
Agree with the difference in ratio and probably props as well. OP doesn't seem to want to research his specs. and calculate his slip.
 
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