I agree that 14 knots on most any of these hulls is not where you want to be unless other factors dictate. On any of the marine dieses in sportboats, something else usually takes the engine out (marinized part failure, waterladen fuel, etc.) vs. I suspect mine will rot apart long before I wear it out. I think in a sportboat that doesn't see in excess of 500 hours per year, they'll both last about as many years if treated right. In a commercial environment, I'd opt for a lower revving bigger engine for "X" horsepower. The flipside is you're engine isn't even breathing hard at spec'd cruise rpm. That will tell you what headroom might really be there. I'd invest in a pyrometer before I started playing around with props though.
If you can hit 4K, loaded, there might be a little headroom on the prop. I think the hotrodded Cummins versions (HO, etc.) are up to 3400, maybe more. The newer Yanmar/BMW engines have a 4000 RPM WOT rating. I'd bet that the Cummins 210 HP in Mistress's boat is probably rated at around 2800 - 2900 RPM WOT. So far as not red-lining the engine, these lighter weight Yanmar marine Diesels are higher revving than what you'd expect in a truck. I'm just guessing that this is what's happening. Fiddle with the trim tab settings a bit to see if there is a better position that keeps you on plane at the lower RPM. If you like cruising 2800 (engine sound, for instance), perhaps you should try running the RPMs up to 3200 - 3400 to get the boat on plane and then back off to 2800. If you can reach RPM, I would think that you should be getting more than 16 at 2800. It may be that you are just below plane speed at 2800 RPM (always on the wrong side of the curve) - it calcs out that you are only doing 16 MPH (<14 Kts) 2800 RPM (based on the numbers you reported) - the hull may be plowing in displacement mode and that requires more power.
0 kommentar(er)
