Carver 405 with 6BT prop size

There are so many variables that would keep the Revs down, Props would be on the bottom of my list.
Was this the boat surveyor or engine surveyor reporting?

Is the bottom and gear spot less clean?
What is the full model number and @ what HP tune?
What is the WOT high idle?
Last fuel filter service?
What does the primary fuel filter bowls look like.
When was the last time the boat made RPM?

To ad on my post #2, any comments on exhaust smoke color???
This could be important.

The 6BT (Not the 6BTA), just broke the 300hp ratings at 2600 RPM.
With the after-cooler (6BTA), more HP was developed at 2800RPM.
On the forward / port side of the engine is the serial number and spec plate.
This Cummins plate offers the HP at RPM. We like for the RPM to go past this number another 100RPM WOT on a light boat.

After a real Cummins tech surveys the engines and checks the governor high idle, he will run the engines, compare real tach readings below with what the dash states and make recommendations.
Engine service may be required, throttle cable adjusted, tach adjustment or just 2 inches of pitch removed from the props. You wont know till a real Cummins tech advises this.

Your fixing to make a heavy investment, even on a Carver, you need to ensure all is correct before your fortunes go into that hole in the water, as it all will eventually go.
It's a boat.

Oh, I forgot;
Welcome to Yacht Forums.
Your tapping on us in the middle of the week.
Hang on a while and others may come on this thread and offer other thoughts.

Your opening line was "Carver 405 with 6BT prop size" .
Now it's 6BTA?
My notes are correct but now you do need 2900 to 3000 on a light boat, WOT.
After high idle and all else is verified.

Still wish for exhaust smoke color when it was at WOT before.

Just making a low offer is not doing your self any favors.
What if the turbos are needing replacement? Injector pump issues? Air cooler fouled?
Long block issues? And More?
Cover Your Assets, Get a real Cummins Tech in there to survey the engine.

Or, have the owner fix all before sale. But still have them surveyed.

What speed thru the water was she making?
Spare props on board?

Once the engines are made right... it's not uncommon to do a WOT test... or use the results you have if the bottom was sufficiently clean and the engines were otherwise running well... then tell the prop shop what RPM you saw and what RPM you want. They can modify pitch, within reason...

20x24 may have just been Carver's best guess, and previous owners may not have done anything to dial in the props...

-Chris

Can't speak to sizes, but Carver is still in business... so you may be able to discuss with them,

If a real prop guy told me the props are "plain worn out" and tuning isn't an option I might believe that. Diesel mechanic, even well meaning, maybe not so much without educated confirmation.

-Chris

Carver Yachts permanently closed July 30, 2021

The main reason props can be “worn out” is galvanic corrosion. Does the metal show any side of discoloration, pink color?

if you give a good prop shop the info on the boat incl displacement, gear ratio, engine size etc they will be able to run the numbers and tell you what is needed. Missing 400rom is BIG deal

unless the boat is exceptionally clean and real cheap I would walk away. Too many things that can be wrong and expensive incl the engines

Ah. Better info. Didn't know. Sorry to have misled...

-Chris

All good brother.
I must had been one of their last phone / support calls earlier that year.
I was telling folk to call them also, till somebody slapped me down with "Their Closed"..
Shame also, That last call was very helpful.
Like the Lurhs, Bertram, Hatterass & other shops closing, lots of boats out there with no factory support.

So, the seller won't make this rite?
Or;
The selling price is that good on a 26 year old boat (near free)?

Dock queen engines may be an issue by itself.
It is the engines that is the only hard value here. The rest is land fill or artificial reef material.
If the engines don't spin up correctly, have been run out of tune, have been run over-loaded, been run full of soot or run with rust on the exhaust valves, it may be more than just removing a couple inches of prop pitch.
Not been running correctly in 18 years means some time has been placed on these engines with it's issue, that your still guessing at..

Not trying to upset you, wish you great luck
But if it is not running correctly before you throw a lot of purchase cash at it, it may take lots more unexpected cash to fix it beyond what you were day-dreaming.

Then, sometimes, good Barn-Finds do Happen..

Well said.