Sea Trial; It went well, then it didn't. AITAH?

We got the boat going, it fired up quick, no smoke, good water flow each side. Gen fired up fast too, and wasn't working under full AC and other loads. Shifts smooth, and engages without drama. We eased out of the harbor and did fine in no wake, everything working well. Settled in at 65PSI oil pressure both engines, and stable at 180F on the temps. Things were going great! Soon to be a yachet owner.

We got out into open water, carrying half fuel and half water, 4 people on board, no isenglass on the fly. About as min wind and weight load as possible. 87F, 66RH, winds 7-9 out of the SW. I've got 1350HP on two D12 TAMD Volvos on tap with 17" props. I don't know the pitch, but they are factory props.

I advanced the throttles, no black smoke, the turbos start doing their job and give us a nice push. We get going at 1800RPM, and it's all smooth, making about 8.8kts. Hmmm, that's a bit low I think? I get approval from the captain, and push it all the way up WOT. We don't get much bow rise, which I'm used to on my 38' twin Yanmars, but maybe this is different. Keep pushing all the way to the stops. Still, not much bow rise, or drop at all. Just a diff of maybe 10deg. This doesn't seem right.

I've got a digital RayMarine suite with radar, depth, temps, environs(whatever?) and speed. Digitals tachs and analog engine gauges. I start trimming, up, down, up, back down, finding the sweet spot. The trim tabs aren't doing much to the ride of the boat, hardly any change in ride angle.

Top out, full bore, all she's got: 2046RPM, and 11.6Kts. I - am - PISSED.

The captain 'takes over'. He can't do any better than I did. We turn around for a pass opposite direction, and get basically the same thing. 2049RPM and 11.7Kts. I - am - PISSED.

I did my diligence and got the factory numbers, and also some real world reports. It should do 2300min at WOT, max is 2375. With ave load, we should be doing at least 16Kts, and more like 20. The broker is talking about cleaning the hull and props, and old gas, and maybe fuel filters are dirty, plenty of excuses, but no more speed to be had.

I told him this was a rejection of the boat, based on **** performance. He's going to haul it, clean up the bottom, clean the props, repl the fuel filters, and we'll try again. So, what min RPM and speed should I demand? Boat and trans, engines have 220 or less hours. It's not overloaded, we're at 1100' elevation, no isenglass in the fly, the engine look and sound perfect. But - this is a deal breaker for me.

Ideas, thoughts, opinions? Am I way out of line to be asking this tub to do better than 12Kts WOT?

Maybe 16.5"? The broker doesn't know for sure but he thinks they are 17". We will know for sure when it gets hauled. There's no record of prop change from mfg, so it's whatever came on the boat from Carver.

Carver 56 Voyager.
OK, it's clear I got the prop size way wrong. I'm going to need to get it hauled and look at it. We are in the middle of the survey. The in-water survey was yesterday, and we were supposed to haul it at 2pm. The lift op was unavail so we did the sea trial first as we had to run the engines to get oil samples.

Bottom line, I'm going to reject the boat if the speed isn't near 17Kts. The rest of the fleet can do it, I better be able to do it unless something is way out of whack.

We are going to have a close look at those too. I had one go bad on my Sea Ray, and it was noticable. Lucky we got to it before it scored the shaft. I repl both while we were on dry.

Let me clarify a bit. The schedule was: wet survey in the slip. Sea Trial. Haul out, dry survey. The wet survey part went great, the few things we found were agreed to fix before sale. Then, the haul out called and cancelled due to illness. We were still on for the sea trial. I'm in the middle of the survey, and this is when the sea trial went Tango Uniform.

I asked when I gave the deposit if we could take the boat out for a ride, and the seller said no to that until the survey was done. Maybe he knew something, maybe not, but it didn't happen. The broker has never moved this boat under its own power. The seller is 85 and in bad health. Anyway, he didn't want people moving his boat until it was time for the survey. I'm $1300 into the survey right now, and another $300 due after the dry check. It HAS to be hauled to clean the bottom. I might find half or more of the bottom paint missing. While I'm a cert scuba diver, and have done that kind of stuff before, there is no way I'm going under that boat with a scrub brush, and get funky. No - way. I have no idea what the cost would be, or if the seller would even allow it.

I will report back after the haul out on Tue and new sea trial. I've advised the broker by email that if it doesn't make 2300 min RPM and about 17kts on plane, we're done and it's rejected.