Too Slow? 2002 Silverton Motor Yacht

[Mer Vin]

I am thinking of buying a 2002 Silverton Motor Yacht with 370 Cummins. I’m open to any input/experience you might be able to share. Specifically, two questions are popping up.
1) The listing states that the boat goes 18 knots at WOT of 2,900 RPM. Seems too slow, what might this indicate? Everything I read for similar boats weighting 24,500 lbs it should be high 20.’s at WOT. A 2002 review of a boat with 385 Cat’s gave a top speed of 28 knots. 2,900 RPM seems right.
2) The motors have 1,940 hours. The listing shows the following maintenance. Should I just be happy it’s done, or worried that there is another underlying problem to fix? What else happens to diesels around 2000 hours?
* Stainless steel risers on both engines in 2023
* New ceramic coated after coolers and turbos 2020
* Main engines and generator raw water pumps replaced 2023

thanks
Doug

 

[kapnD]

Crunch some numbers on a propeller calculator, to make sure that you’re in spec there.
An accurate, and actual weight reading will help a lot. Boats gain weight over the years.
Beyond that, clean bottom and running gear can really knock down top speed, and overload motors.
If my memory serves me correctly, you should be seeing more like 3100 rpm at wot.

 

[Mer Vin]

Thanks for the feedback. I spent a lot of time on the Boat Diesel Prop Calculator, which helped clarify the issues. The props on the boat are correct. At 2,900 WOT it using 9% extra power. If it's only making 18 knots at WOT that's 22% below expected speed indicating engine problems (bottom is clean and props are correct). An extra 2000 lbs only changes the speed by 0.8 knots. I suspect the listing is worded incorrectly, time to dig in with the data.

Thanks for steering me to the calculator.

Doug