Hampton 630 motoryacht

I have spent more time sitting on the toilet on yachts, then you have spent on them. I have forgotten more about yachts than you will ever learn. Everything in my thread is accurate. I have read your thread, I have extensive experience with the sistership to YOUR boat, and my figures on fuel burn and speed are accurate. I can also tell you where every access panel, every piece of equipment, and every nuance to your boat is. including the dozens and dozens of Y valves on all of the drains for a/c's, sinks, etc. Hampton hasn't quite figured out how water is supposed to drain. Like how you don't run a 3/4" master shower sump pump discharge hose with an 1100 gph pump to a Y fitting that also has 2 air conditioning condensate drains that gravity drain, then have the common discharge hose the same size and the discharge fitting just below the waterline so that when 1 barnacle grows in it that restricts it 30% you have grey water from your shower shooting out of your master a/c drain pan and all over the closet. OR, how the Flybridge sink shouldn't have a 3/4" drain line that runs 10' down to a Y that also has the FB air handlers also running into the same Y and the discharge hose the same size, so that when you run the sink for a few minutes it backs up and drains really slow when everything is clear and comes out the air handler on the FB. FB sinks should have a 1 1/4" drain hose to begin with. Ohhhh, and how every pump on the breaker panel, turning the breaker on for the sump pumps, bilge pumps etc. puts them on ALL of the time, so brokers turn the breakers on and most captains and burn all of the pumps up.....and how the boat has dozens and dozens of 1980's glass fuses hidden rather than relying on the breakers.

800 RPM's gets you over 8 knots at 8 GPH or less on both engines.
If you want to treat a yacht like a sailboat, why didn't you simply buy a sailboat, rather than quickly destroying every system on your yacht? Perhaps you should give CAT a call and ask them how their engines will fare with what you're doing to them? If you are such an expert, why on earth did you come here to ask for everyone's advice and then argue with everything every expert on this forum has told you? If you are THE expert, WHY ARE YOU HERE????

For the master sump box. In the master walk in closet, you pull out both drawers on the inbound side of the closet, behind those is a white hatch, behind the white hatch is the sump box and clean out for the sump box. BUT, chances are the Y is semi clogged, OR the thru hull discharge has a barnacle in it because it's slightly below the waterline. The Y is located behind the wood panel on the outbound side of the closet below the air handler. Air handler is in the top, aft, outbound side of walk in closet aft of master bed. Not to mention the a/c drain pan lines will be sagging and not supported properly, so you can fix that while you're in there......seems like I'm in there every 3-6 months!!!!!!!!!!! Buy a 24 volt 1100 gph rule mate pump, because they go bad all of the time and is probably whats wrong if the shower is draining really slow.

BTW. The boat has a hydraulic pressure gauge right at the front of the engine room on the front bulkhead, just to starboard of the aisle. The Wesmars should be 800-900 psi to run properly.

That's exactly where it is on the Hampton 620 I have managed and maintained for over 4 years now. I can most likely even find pictures on my phone if I look hard enough as I had all of that apart 2 months ago for the above mentioned issues. Considering Hampton never made a 630, I'm not quite sure what YOU are talking about. Hampton made a 620 which is now replaced by their 650, which can also be verified by looking up the 620 under previous models on Hampton's website. The owner of the Hampton I take care of, uses it for it's intended purpose as a YACHT, does love the boat, it's his favorite and it's his 17th yacht, and the Wesmar stabilizers work perfectly because they are being utilized in the manner they and the yacht were designed for which is utilizing both of it's engines. The boat is very stable both at 8 knots and 20 knots cruise...…..wet, but very stable and a good ride.

Here is Hamptons section of all retired yachts, on the Hampton Yachts website. Nowhere is there any mention of a 630.
https://www.hamptonyachts.com/models/retired#

They did make a 630 PH based on the hull of the 680 around 2007

This question was a fit for task question. Hardly fair to judge a boat based on what it's not really designed for. I would venture an opinion that many boats would not perform well at 8 knots on one engine. I can't imagine any of ours would. Clearly, the stabilizers weren't designed for that use. It's like buying a Ferrari and saying it's lousy at towing my boat. This doesn't mean you might not be happy with the Hampton, but don't criticize it for doing a poor job at something it was not designed for.

Also, don't compare everything to some sailboat you once owned. If that sailboat is your ideal boat, then why don't you have it or one like it now? You can't judge different types of boats against each other fairly. It would be like me buying a full displacement Burger and then complaining because of how slow it is.

Bad Kitty , when I'm stinkin' my way on the Chesapeake bay over the years during a sunny perfect 20mph blow, I am always amazed to see a few sailboats with there sails in/down...just motoring along..really?
I suspect you were not one of "those" sailors.
But with your new power boat, you are now a ''stinker'' and you are running you boat like the captain with the sails down in the wind.

I would heed what Capt. J said. run with both engines and bump up the rpm's a bit and you boat will perform like a dream.

A very reputable Cat surveyor recommended running on one engine at higher rpm's when making long cruises in open water. He said modern gears will handle being off line for fours hours then switch to the other engine. It will cut engine hours in half for maintenance and much better for the high performance engines at more rpm and load. His point was it saved run hours and maintenance at about the same fuel burn and better for any high performance engine. Makes sense for longer cruises in the right conditions.

Well, I'm not a very reputable CAT surveyor but I respectfully disagree. CAT says best to measure engine live in fuel consumed. By following what is outlined in your statement, that changes the fuel consumed by each engine very little. They each consume nearly double the fuel for half the time. CAT says fuel burn, not hours, is the most indicative number. Hours is just a convenience and approximation.

Now, you also said one engine at higher RPM, but there's no indication the OP does that. By all indication he runs one but still at low RPM, at 1250 RPM to be precise.

Now, as it applies in this case, the drives are both well off the center line and running one as opposed to two does impact the angle of propulsion and the effectiveness of the stabilizers. Your shaft and prop are to the side by a significant amount with no counterbalance. They are also very near one stabilizer and distant from the other which could contribute to the "jerky" actuator arms. To what degree this impacts it, I can't say, nor can the engineers I've spoken to say. What we can say clearly is that the boat was not designed with running on one engine at 8 knots in mind. Therefore, to criticize how it runs or it's stabilization in those circumstances isn't really reasonable. My wife equated it to running her Porsche on three wheels. If you had two engines on a single shaft and chose to run only one, it would be different. I see triple engines which allow running just the middle or just the two outside, but never a recommendation of running one of the outside engines. Note that Wesmar basically said the same, that if you're going to run it like this, you have the wrong size stabilizers.

It sounds like the OP has a boat that is not ideal for his primary use and now must figure out how to make it fit that use better. Things like larger stabilizers might help but no one can be sure as the boat hasn't been tested on running one engine and having larger stabilizers. Another option is different stabilizers but clearly not an option Wesmar would propose. Now, any of these changes would also make the boat perform poorer used as it was designed to be used. Ultimately, the OP has to decide whether to accept the shortcomings as he sees them, to make changes trying to address them, to run the boat differently, or to get a different boat.

As to comments from other Hampton owners, they're not likely to be very helpful, because those owners aren't running their boat the same way he is.

OB, was replying to OP wanting to run 1250 rpm around 8 kts not running hard on single engine. I hardly see where that would be a problem for open water straight line cruising, with the exception of the stabilizer performance he was having. Cat does rate their engines by total fuel burn. Just had a conversation with my Cat mechanic during a sea trial this week and his comment for our 3406E's are designed to perform best around 80% load and rated at 1o,000 hrs life with good maintenance. My point to the OP was (according to my engine surveyor) there is nothing wrong with running his Hampton at that rpm and speed on a single engine and was better for the engines than lower rpm operation running both. Besides cutting scheduled maintenance in half is not a bad thing either, would buy a lot of fuel and beer.

YES there is something majorly wrong running 1 engine at 1250 rpms in a boat that is propped for twin engines. CAT and most other engine manufacturers require the engines to be propped to achieve WOT at 2300 rpms or better (whatever the engine is rated for RPM's) in this case 2300 rpms. If the boat is propped based on BOTH engines at WOT and the engines making 2300 rpms utilizing both. Running on only 1 engine at 1250 rpms results in a severely overloaded engine (excessive load factor for RPM point) at that RPM in the propeller curve because it is only utilizing one engine. If the boat was built with the same engine in a single engine application, it would be swinging a propeller with a hell of a lot less pitch. Now, you add that the boat is crabbing and the rudders are fairly hard over creating more drag, AND the stabilizer fins being cocked over to try to make up for the unusual rocking due to the crabbing and you're overloading the engine leading to a very short life. CAT C18's burn very little fuel under 1000 rpms (almost all diesels sip fuel under 1000), and in that boat around 800 rpms, gets you 8 knots and a total of 8gph with BOTH engines and it will ride right and be stable with the stabilizers because it's tracking straight . At 1250 rpms you're spinning the turbo and burning considerably more fuel, 12.5 GPH for the 1 engine at 1250 rpms and probably at 80% load or higher because you're overpropped.

Whoa! School is in session! Very well put and explained Capt J. That's something I never gave much though about. Your YFs name should be elevated to Professor Capt J !

Capt J, that is some good intel. Figured there would be no fuel savings running one engine but never thought there would be 80% load or more at 1250 rpm. Running both at 800 to 900 to get that 1 mile to the gallon is probably normal for boats such as the OP's 63 Hampton, but still not good for the HP engines. I agree with you about running booth engines because that is how most of us operate when cruising. I was surprised when told about running one engine for extended cruising, but it made sense reducing run time per engine at same speed and fuel burn. Apparently will not work if stabilizers are needed. Did you actually see 80% load at 1250 on a C18 in that mode?

Pascal, I knew you would have some numbers tuck away in that file. Yep, just splitting hairs. The only time we have ran on one engine was also because of mechanical problems. Running at 8 kts does build hours on engines, gears, and generator per mile, when you add the scheduled maintenance the cost per mile is not so good.

A lot of this is basic knowledge...but I will admit often basic knowledge is dangerous...unless of course it's coupled with intimate knowledge and educated experience...like it is in this case...While I do not believe there is 80% load to achieve 1250 rpm...I agree that it takes a lot more load to turn that prop 1250 RPM's then it would require to turn that prop 1250 rpm's when running both engines..hence the over load situation. Just an tid bit...diesels generally burn 1 gallon for every 20 hp utilized...throw out the below 1000 rpm's and those over 80% load. So 12.5 gallons an hour is about 250 hp of the engine being utilized...I learned something tonight. Thanks Capt J