Professional help needed-QSD4.2

[corsair.p]

Please can anyone tell me if there are any hardware differences between QSD4.2ES270S and QSD4.2ES350S or they just have software differences?
IS there any chance to convert the 270 to 350 with some reasonable cost?
I designed a 38ft with twin QSD4.2ES320S and bravo I expected to run 28kn at 10.3tons, but the boat was built 3tons heavier and the engine was changed to QSD4.2ES270S and Bravo II by a lot of unexpected and stupid reasons,now the boat can not get over the hump to plan and only can run 12kn.
It was a disaster and i really need some help,thanks.
The boat have:
Waterline length =9.25m
Chine beam =3.38m
VCG=1.45m
LCG =3.565 from transom bottom.
Deadrise @transom=18.26 degree
Deadrise @midship=19.75 degree
Frontal area of upper waterline = 6.2m2
Chine width=170mm with 3.5degree reverse angle

 

[Aliboy]

I can't tell you all the differences, but it may not be just a SW change. I Would be checking to see if the turbos are the same as one obvious possible difference and also the cooling systems.

To be honest I wouldn't be too happy running those engines at 350hp. They may not last too long. The drive is also a possible issue. Bravo 2 is much more suitable than Bravo 1, but those Bravo drives don't seem to last long on the 350hp diesels. at the very least you need to fit drive showers to them.

I am interested to hear that your boat won't plane with a pair of 270hp diesels.Are you sure that it has the correct props and that the drives are mounted too low? I own a 43ft game fishing boat that runs twin 330hp diesels on shafts and I don't need to use anything like the full hp to get planing. My boat also has a medium V deadrise, so not that different to your boat and almost identical weights. Before doing too much more I would look carefully at the setup of your existing drives and see why you can't get better performance with what you have.

 

[baeckmo]

Before digging into Engines: what is the total weight, fully equipped and including fuel and crew?

 

[WestVanHan]

The first and simplest thing to check is if the props are spec'd properly.

At a boatyard a few years ago was something like this on a new build.
Three weeks of fooling around trying to get more power,moving batteries around, swearing at the NA,etc and someone got the idea to check the props-they were an inch too pitched...