Have a 2000 Carver 396 MY with 7.4MPI mercruisers with only 276/296 hours on the engines.
On the original sea trial for purchase, she would only turn 3400 rpm's on each engine, (they were identical), found out the risers and manifolds were in terrible shape, so had them replaced, hoping that would help the rpms. No help at all to the rpms, exactly the same as before 3400, but engines are running nice and cool. Had the injectors removed and inspected and 8 of them were totally fouled, replaced them all, changed the fuel filters and added fresh fuel, (fuel was low during initial runs). This time I was expecting a big change in rpms as the engines started easier and sounded smoother, but absolutely no change to rpms at all, still tops out at 3400.
The bottom is clean, the running gear is clean, the props are original, (24x25 4 bladed nibrals), gears are original, (Hurth 800A with a ratio of 2.8:1. Compression is good on all cylinders and oil samples were good as well.
Fuel pressure is being checked next, but doesnt seem that the failure could be so identical for each engine?
The hull had a moisture reading taken, was normal and there is no water in the bilge anywhere.
She does have the single lever controls, which seem to have excessive play, but my tech says they go all the way to the stops on the engines.
The weirdest thing is that both are identical, its usually one engine or the other?
Does anyone have any idea what we could be missing here? At 3400 she will not get on a plane and just plows and plows and nothing has made any changes?
Any help would be greatly appreciated?