Our Mainship is one of the later production 390 models, built at the peak of their popularity. By the time this one was built, Mainship had added a number of customer-driven features and upgrades, and had the benefit of more than five years and almost 400 hulls worth of experience in perfecting the design. She has all of the most popular options including the Stainless Steel Sampson Post, single Yanmar engine with bow-thruster, Cherry-and-Holly sole and the (rare) folding mast.
Single Yanmar 370hp Diesel (~1,100 hours)Upgraded exhaust; high-rise elbow and Centek backflow check valve
Kohler 8kW Genset
New Water Pump (2017) and New Heat Exchanger (2017)
New Dinghy (2016), Outboard (2016) and Davits
Raymarine Autopilot, Color Chartplotter/Sonar/Radar
Cherry interior, Cherry and Holly Cabin Sole
Bow-Thruster; Side-Power SP-95T
Optional Stainless Steel Sampson Post
Optional Folding Mast
Stainless Steel Railings
Interior LED Lighting conversion (2015)
New Flybridge Upholstery/Cushions (2017)
Newer Nova-Kool Refrigerator (2013)
Two new Air-Conditioning units (2016, 2017)
Both with transferrable 3-yr Extended Warranties from West Marine
New A/C circulation pump (2016)
Excellent condition, expertly maintained, located in Bradenton, FL $143,000
"Cruise speed" (as it is usually defined) is around 17mph @ 2,500 rpm, but we don't ever run that fast. The running angle is too high, the wake is enormous and...well...just too much drama being up on 'plane', with a hull that isn't really built for planing and with a high -center-of-gravity to boot.
We run her like a displacement-hull trawler, right at or a little above hull speed (8-10 mph). Once or twice we put her up on plane for an hour or so to outrun a front. Each time she goes out we do run her up to near WOT for a 3-5 minutes just because we hear you're supposed to do that.
We've not ever measured fuel burn carefully. A flow-scan was on my list, but after our first few longer trips, we were so surprised by how little fuel we used that the money for a flo-scan didn't make any sense.
I like to go slow, keeping the bow down and the wake small -- so we typically run her between 1,100 - 1,500rpm. At 1,100 we see about 8mph in calm water and about 7 miles-per-gallon. At 1,500 rpm we see about 10.5 mph and about 3.5 mpg.
In 1998 Capt. Bill Pike did a review in Boating magazine of the MS390 in both the single and twin version (attached).
He measured 20 mpg (!??!) at 900 rpm and 12.4 mpg at 1,200 rpm. Not sure we have ever seen numbers like this...but maybe with a light load, fresh bottom job and >>perfect<< conditions???
Bottom line, a single engine semi-displacement hull, running at hull speed is going to be very fuel efficient. We have been extremely happy with the fuel consumption.
One thing to notice -- look how much the fuel burn increases when you compare the single to the twin-engine version...
Agreed, they really are great boats, and underrated as far as construction/manufacturing quality goes. And they got better with time (once they got many of the 'bugs' worked out).
Regarding the fuel-burn charts, I have never confirmed .4 gph at 900rpm with my Yanmar, but Bill Pike's tests were conducted with a single Cat vs. Twin Volvos.
In the Cat 3116 documentation, that engine actually does burn only 2.2 GPH at 1400 RPM according the published curves. That's about exactly what the test reports said.
Now..whether the boat will actually go 8mph at 900rpm is another story. With a brand new bottom and propeller...maybe...and a stiff wind at your back... ;-)
Re: "The twin engine version of the SAME boat will burn very close to the SAME fuel at the SAME speed. Horsepower required to go xxx mph is virtually the same regardless if you have one or two engines."
Not quite true. Before I bought the boat I tracked down Jim Krueger (former GM and VP of Operations for Mainship) and asked him about the fuel numbers from that particular test. I too was of the opinion that the twin-engine version should burn similar fuel at similar speed.
Krueger pointed out that while equal HP generally does burn equal fuel regardless of the number of engines) with the twins there is substantial extra horsepower needed to drag TWO prop-shafts, struts and rudders through the water, compared to the single where the prop-shaft is on the centerline, and buried in the keel. Since the keel is there (and adding some drag) whether you have twins or the single, the twins should be expected to present more than 2x the hydrodynamic drag compared to the single.
Especially at low speeds, it takes very little extra drag to slow you down, and from this perspective it is obvious to me that the twins would burn a lot more fuel.
Bill Pike has an excellent reputation in the industry, and I'm inclined to believe the numbers he got (at least those above 1200rpm) for the twin vs. the single.
Steve Cyr (Stella Blue's owner) used to hang out here -- maybe he is still here?
MS 400 is both longer and heavier than the 390. The actual LWL on the 390 is 35' (minus the submerged swim-platform) while the MS 400 is 40' LWL. I think the beam is the same. One story I heard is that the MS 400s were laid up in MS390 molds that had simply been 'stretched'. No idea if that is true or not.
We have the same boat, model and year. We wish we had the folding mast. Could you send a pictures and any relevant dimensions. We have aske the yard where our boat is on the hard for an estimate to fold the mast.
We had the mast hinged on our 1997 MS350 in 2003. The yard cut it at about halfway up, making it real easy to single hand it up or down. Total cost was $1,800. They even made a little stand for it as well that it rests on when in the down position. We cruise the Erie Canal every year so the hinge was a must!
To close out here...if you calculate how many GPH are required to produce (for example) 80hp when comparing singles to twins, the number you will come up with is about 10-12% 'penalty' for using twins (like you said). Steve Zimmerman recently showed us this math over at Passagemaker. This is an accurate 'theoretical' number but it completely ignores hydrodynamics.
When all other things are equal, it takes substantially MORE horsepower to move any given hull through the water if it has twins vs single. The simple reason for this is that a twin-engine configuration presents (a) much more drag from running gear and (b) will weigh more and increase the wetted surface of the hull.
So...10-12% is only the starting point.
How much extra horsepower needed to overcome the extra drag will be a function of the design of the hull and running gear. Take for example a single-engine semi-displacement trawler that has the prop-shaft buried in a keel (Mainship 390), therefore does not need a strut. The only thing you are dragging through the water is the hull and the rudder. Now let's build a twin engine version in the same identical hull. The twin configuration is dragging two prop shafts, two struts and one additional rudder through the water, and the wetted surface of the hull has increased because of the additional weight (about 2,000 lbs extra in the MS390).
From this perspective it should be obvious that a single vs. twin configuration will save you far more than the simple engine horsepower math might lead you to believe. The difference in fuel burn will be greatest at slow (displacement) speeds, where hydrodynamic drag from extra running gear is a large percentage of total drag. As speeds increase, HP needed to overcome additional drag becomes a smaller percentage of the total, but you never get anywhere near the ~10% number you cited. At 10.5 mph (according the the charts I posted), the twin version is burning 1.7x the fuel of the single. The single will go 1,700 miles on the same fuel that the twin will consume in 1,000 miles.
It may help to think of this from another perspective. At 1,200 rpm, my Yanmar 6LYA is only making about 35hp but it is moving the boat at about 8.5mph! The boat is behaving very much like a sailboat under power, and any drag will slow you down, significantly.
We just bought the 2007 Mainship 400 and brought her up to Newport from New Bern in April. We really love her! After 30 years of sailing, she was easy to get used to!
One question for you, though, have you had any trouble with the stern decking getting soft? When we step onto the boat there is a bit of give and we are planning on having a marine mechanic put up the decking to check.
Some one told us this softness was "typical" of Mainships.
The MS400 and MS390 share a very similar design of the decking inside the cockpit. There is a common factory manufacturing defect in the structure that supports the deck in this area (on the PORT side only). It is easily corrected (once detected) but it is >>not<< easy to detect it. If this problem is not addressed in a timely fashion, the result will be a soft deck in this area. This is not so much a big deal to repair, but it is a big P.I.T.A. if you let it go too long. I know this from painful personal experience.
If you have a soft deck on the port side of your MS390/MS400 cockpit (aft deck) area, please send me a private message and I can talk you through what to look for and how to fix it.