Planing Hulls with Twin Diesels...Economical?

[gosstyla]

Other than being out of your price range a "trawler" catamaran would likely meet your objectives.

[jm21]

Yes, A trawler catamaran would be great but way out of the price range.

I'm not sure how much of a difference there is between 6 knots and 8 knots for weekend trips, but trawlers do have a ton of space and amenities. A ~34' trawler is still in my sights. Maybe a good deal on a sunbridge.

[Mule]

My $.o2... I just bought a Mainship, with a repower from Perkins to Cummins. 200 hp is more than enough, though I have 250. There is more under "I be one of ya" thread.

I, like you could afford about 50k total. A large part of my decision was baised on which boats were being repowered in the recreational fleet. Mainships are. My logic is that if people are spending the bucks to repower then they must be a good platform. I paid 34 and not to worry I will hit 50 after routine bottom work, new Air, electronics, redoing the cored flybridge floor, rewiring and so forth without breaking a sweat.

That does not mean the boats do not have some warts but in the greand scheme of things any high production boat that is being repowered in siginificant numbers must be good. The 1975 to 85 900+ 34 Mainships have issues with coring on the flybridge.

As for the bayliners, I feel they likely got a bad rep due to the poor quality smaller boats they put out. They were called bay "liners" for a reason. The largerones I have been told were pretty well built. The question that begs to be answered is, "Are they being repowered?"

mainship : This list is for Mainship Owners and others who want to own a Mainship.

Go to this website and almost more than you will ever want to know will be provided for you.

[robw_fl]

I personally have a hard time finding any advantages to gas engines over diesels, aside from an initial savings when purchasing.

As for docking one of the um...well, less than stable boats where they forgot to put any of it underwater...the best way when short or single-handed is not to try to do the scramble all over the deck and get them all. Just snub the midship line as tight as possible on a cleat or piling right next to the midship cleat and you're done. One line, and you're tied up. Then take you're time getting the rest of them.

If you're feeling like a traitor looking at powerboats, don't - if you end up with one of those - you'll have as much of a sailboat as a powerboat.

And I agree - bayliners are not the way to go. They have a reputation for a reason.

GOod luck though, no matter which direction you go...

Rob

[RaySea Lady]

Just wanted to reply to the fuel efficiency issue.

I have a 65 OAL Bluewater with twin cummins 450hp,

The following stats are from a Motor Yatch Magazine review and it is pretty much what I get.

800 rpm (Idle) 6.5 Knots 1.7 gph
1500 rpm 9.8 Knots 9.6 gph
1750 rpm (Planing speed) 11.1 Knots 14.2 gph
2800 rpm (WOT) 22.0 Knots 50.8 gph

As you can see, if you want to run a cruiser at Trawler speeds they are pretty economical also. And this is with a 54000 lb displacement.

Not sure that half the displacement would be half the fuel but there would certainly be a major difference.

Diesels are definitely more fuel efficient than gas.

[RaySea Lady]

Originally Posted by jm21

From what I'm reading it sounds like the higher repair and replacement costs for the diesels outweigh the fuel savings.

My 450 cummins have 1300 hours on them and not much in repairs other than oil, filters and raw water impeller pumps every couple of years, and they are in great shape. Just had a cummins diesel tech go over them last month.

I don't know what repairs one could expect on gas engines with similar hours.

[RaySea Lady]

Originally Posted by GonzoF1

Yea... I've seen Carvers that made me scratch my head and ask the same question.

"So you have to go from the bow, run across the deck, up the stairs, down either the cockpit stairs or down the ladder, then open the surround glass to grab the stern line?... Ummm... Good luck with that on a rainy day Mrs. First Mate." :-)

Not sure what equipment the carver had, but on mine, I dock it alone and I also have to go to the upper deck and down to the cockpit.

But I have dual thrusters and I also have a mather portable helm that I take with me down to the bow and to the cockpit. It gives me full control of my engines and thrusters. So, with the right equipment, it is easy.

I would rather dock my twin engine 65 footer than a single engine 25 footer.

[boatpoker]

My Dave Martin designed "Trendsetter 40" with two heads, two staterooms, saloon, dinette and galley will cruise at 8 knots at 1.4 imp. gallons per hr. with a top speed of 20 knots at 4.5 gallons per hour with a single 235 Volvo TAMD 60B.
Power boats do not have to be fuel guzzlers !

[jm21]

Originally Posted by RaySea Lady

Just wanted to reply to the fuel efficiency issue.

I have a 65 OAL Bluewater with twin cummins 450hp,

The following stats are from a Motor Yatch Magazine review and it is pretty much what I get.

800 rpm (Idle) 6.5 Knots 1.7 gph
1500 rpm 9.8 Knots 9.6 gph
1750 rpm (Planing speed) 11.1 Knots 14.2 gph
2800 rpm (WOT) 22.0 Knots 50.8 gph

As you can see, if you want to run a cruiser at Trawler speeds they are pretty economical also. And this is with a 54000 lb displacement.

Isn't it bad for the engines to run at that low of rpm though? I had always heard diesels should be run at about 80% of max rpm.

50 GPH...my god...

I am pretty young and was a poor college then grad student for years, so I don't have much in the way of stuff. One of the main reasons I'd like to try the lifestyle out now, while I haven't accumulated much and most things I can get rid of without any heartbreak.

[RaySea Lady]

Originally Posted by jm21

Isn't it bad for the engines to run at that low of rpm though? I had always heard diesels should be run at about 80% of max rpm.

50 GPH...my god...

.

Yes, it is normally bad because the oil does not get up to the required temperature to lubricate properly, but my engines have compensators for that, the oil pump does not start until the engine gets up to the proper temperature to insure proper lube so that they can run at low rpm without damage. A cummins option.

the 50 gph is not what I run at normally but it is nice to have if you have to get to port to avoid a storm or some other emergency.

[cat man do]

Originally Posted by boatpoker

My Dave Martin designed "Trendsetter 40" with two heads, two staterooms, saloon, dinette and galley will cruise at 8 knots at 1.4 imp. gallons per hr. with a top speed of 20 knots at 4.5 gallons per hour with a single 235 Volvo TAMD 60B.
Power boats do not have to be fuel guzzlers !

Never heard of them any more info?
Google wasn't my friend

[boatpoker]

I just up loaded a few pictures of the Trendsetter 40 to my "photo album". I have never used this feature of the forum before. I believe you have to go to my profile to look at the album. Let me know if I have that right.

[jm21]

Is it possible to run gas engines at near idle and have them still be healthy?

There are plenty of cheap gas-powered powerboats out on the market right now...awfully tempting until I think how much it would cost to get to Friday Harbor and back. But I guess the money you'd save by getting say an old planing boat instead of an old trawler would pay for a whole lot of gas.

And if weight is a big deal it seems like the ~10,000 lbs sunbridges should get way better mileage than the ~17,000 lbs flybridges?

[LtBrett]

There is a large bias on this board towards long range cruising, thus the recommendations for hull speed and diesel power. Let me put a different spin on it. Fuel should be a small part of your budget. You are looking at older boats that will most likely need substantial refit. If your entire budget is $50k, I wouldn't look at boats priced much over $30k, then plan on using the rest of the budget to make her yours. For a weekend cruiser like you, diesels are an order of magnitude more expensive than gassers, both on the initial purchase price then on the annual maintenance. Gas engines are simple to repair and parts are much cheaper (I'm writing in very general terms here). Do the math--30% less fuel used vs. higher initial and ongoing costs. Unless you are putting over 200 hours per year on the engines, the math isn't even close.

Now for displacement vs planing. How far do you intend to go? How much time do you have to spend? If you are primarily making weekend trips, a planing hull is probably preferable so you can get where you want to go and have some time to spend there. You can run a planing hull at displacement speeds, perhaps 6kts, while maintaining good fuel economy. But you'll probably end up cruising on plane and simply budgeting for it. To answer you question about idling gas engines, yes, you can. They are not subject to the same kind of fouling diesels are.

One last note: IIRC, Bayliner motor yachts are completely different beasts from other boats in the Bayliner series, and are much higher quality.

The best boat for you comes down to how you you intend to use it.

Brett

[jm21]

I don't suppose anyone's ever thought of putting on a 50hp or so outboard on a planing boat and motoring at displacement speeds? It seems like with a new efficient outboard that might work pretty well, and would probably save a ton on maintenance compared to idling two inboards. Would look pretty silly and you'd probably have a lot of people asking you if you had engine problems, but...

So what's the advantage of the trawler if you can get almost as good mileage on a planing hull if you idle the engines? Just that the trawlers are built to be a bit more stable (e.g. with a small keel) and they seem to be typically built with more amenities and tankage?

Sorry for all the newbie questions. I'm not very familiar with powerboats at all.