Inboard/Outboard vs Inboard

[Alan Peck]

I know this question is pretty broad to be answered in a few words. But, what are the general pros and cons of an Inboard/Outboard versus an Inboard.

I am thinking of building a 23 foot "lobster boat" I am not interested in great speed.

I have owned several outboards, but never a Inboard/Outboard or inboard.

I am wondering about cost, ease of installation, maintenance, fuel economy, etc.

I am thinking of a engine in the 75 to 110 hp range.

For use only a couple of dozen or so times a year, is it worth the (significant?) increase in cost to consider diesel over gasoline.

Thanks for any thoughts.

[WWheeler]

much pondering over this issue up my way.

diesel is easily twice the price, BUT it's safer.
diesel fuel is cheaper, BUT only if you're actually using the boat.
diesel is more reliably and easier to maintain, BUT infrequent use is bad for it. (condensation causes water in fuel, fuel gums up injectors etc.)
diesel has a lower power to weight ratio, BUT in most boats, who cares?

there's a real attraction to diesel because it promises long and hardy life, with low operating costs. however, this could be a sucker trap, if you attract some big mechanics bills.

I understand from other threads that inboard/outboard has better manouevring at lower speeds, good for canals / rivers with restricted speeds. Fixed propellers, however, has lower operating costs over the long term. (again, for infrequent use, this is harder to justify).

[Ian McColgin]

I am not a fan of gas engins, but in your case that might be the way to go. Cost matters. Also gas engins are often lighter, though this is less pronounced than in days of yore. Fuel costs have closed.

It's not at all hard to make gas a perfectly safe installation. On the other hand, it may be a bit crankier to start on a muggy day after a week's neglect.

Were I you, I'd be tempted to go all the way with an outboard. Designing a cover so you don't have to see the thing is a challenge, both to get enough air to the OB and to handle cooling water correctly, but Gerr and many other designers have solved that one. So why not stick the smelly thing all the way out there?

[gary porter]

Alan, I'm with Ian,,,I'd go for the Outboard, something like the 100hp Yamaha four-stroke. Quiet, economical , easy to maintain, plenty of power. Outdrive units for Inboard/Outboard are often a source of high maint. The inboard , in a 23' boat takes up considerable deck space etc.
IMHO...Gary

[Donn]

Ian's right...for a 23' boat, used only 25 times a year, an outboard will be cheaper in the long run, and much easier to service/have serviced. You'll keep all the interior space of the vessel for passengers and gear, without cluttering it up with the heat and noise of the engine.

I couldn't disagree with WWheeler's comments on diesel any more. It is, by far, the most proven propulsion system in marine use, and has been for quite some time. Initial costs may be higher, and may not be. Fuel economy, fuel cost, maintenance costs, and overall reliability will easily overcome any additional initial expense. Diesel engines are more economical to run at all speeds, and under all loads.

PS...almost forgot...diesel smoke smells like ambrosia! :D

[ 08-09-2002, 04:59 PM: Message edited by: donnwest ]

[ishmael]

If not interested in great speed, why build a planing hull?

How about a displacement launch or, for simplicity's sake and greater seaworthiness, a dory ala the St. Pierre? You could buy a used, slow turning Sabb(as are available quite often now that the fast, light Yanmars with reduction gear have come into vogue). Marvelous for pottering about, and with the right boat, even some extended cruising.

What is the boat to be used for? Always the question.

Jack

[rbgarr]

To add more confusion there's the inboard engine mounted amidships with jackshaft to through-the transom i/o drive unit!

[Alan Peck]

Thanks for all the input.

The boat would be used mostly in large bays and along the north Florida coast line in the Gulf of Mexico. Most of the time would just be puttering around with the occasional Gulf fishing trip which might be up to five miles offshore.

As I mentioned, I am not really interested in speed, except that we have freguent afternoon thunderstorms in the summer. Some of them can be quite severe. So a reasonalble turn of speed to help avoid the storms would be nice.

Based on advice so far, it sounds like the outboard has a lot of advantages.

I would like to know more about the idea of a mid-ships mounted inboard driving an stern mounted drive through a jack shaft. I've never seen that before.

Thanks again for the ideas.

[CharlieZ]

Our 23' MacKenzie is similar to your requirements and that configuration is near perfect for me. Definitely wouldn't go any smaller with an inboard, but Gawd an inboard is better propulsion: simpler, lasts far longer and costs far less to maintain. Can't have a tiller on the transom with an OB/IO, either. ;)

I'd love to have a diesel, but the $14k+ premium buys a lot of gas.

Regards,

Charlie

[John M]

My brother-in-law owned a 16 ft boat with an IB/OB. Nice boat. Pulled skiers. Very fast. He kept it in the water on a lake. A beaver ate through the rubber housing that surrounds the prop, the boat sank at the dock, and the insurance company totaled it. I believe he has given up boating for a while.

John M.

[Donn]

"I'd love to have a diesel, but the $14k+ premium buys a lot of gas."

$14K+ premium? What diesels are you looking at? I see good used diesels down here for under $5K, pretty regularly.

[CharlieZ]

Apples to apples: new gas to new diesel.

[Donn]

Charlie...is your MacKenzie new? BTW...is it a bass boat? Got a pic?

There's no reason to buy a new diesel (not that I wouldn't love to have a pair of new ones..my diesel wrench quoted me $40K installed for 2 new 100HP engines...said they'd take half the space of my old Nissans, and I wouldn't be able to hear or smell them). You can find used diesels with lots of life left in them, especially if you look for industrial rated engines.

[ 08-12-2002, 02:34 PM: Message edited by: donnwest ]

[Sheep]

Alan, perhaps I can return a bit of info. The last boat I owned was a custom 18'5'/8'4" CC. The local fellow who built them like tanks in f/g also built several 25'ers using a single FWC 330hp 454 with the engine deep under console and with jackshaft. You "lose" a tad bit more power (you'll never notice it!!!) due to rotating mass of shaft but for shallow areas, you can't beat that arrangement. Inherently nice balance with motor amidship and no motor box, and the ability to trim the boat as with outboard. IF I were going to that size boat again, I'd definitely consider it, but the person doing it better be meticulous in his setup. The man who bought the bought to use primarily as a king mackerel boat offshore loves it. Albemarle, a premium f/g built down here offers models with jackshafts to get motorbox off the transom to fight big offshore fish. Adding a transom/swim platform adds even more to practicality and usefulness. Big gas engines run at slower RPM's have wonderful longevity/economy, but 350cu in may be all you'll ever need.

[ 08-12-2002, 05:18 PM: Message edited by: Sheep ]

[CharlieZ]

Don,

She's presently a turf trawler; I'm redecking and re-garboarding now. She's a 23' bass boat built in '73; looks like a heavy-duty Lyman.

I wish there were new ones, but they're too wet for modern tastes. The closest design is the Eldridge-McInnis 25' listed by WB, which are more refined and a bit dryer, I am told. I wanted to go back to the Mac "guide boat" config, but the original owner is around and won't let me... ;)

I hear that there's a guy up your way that's good with Macs.

Charlie

[Donn]

Charlie...I know exactly what she looks like..."turf trawler"...I like that. When I was shopping for something to fill my shed with, I looked at several Cuttyhunks and Guides...dandy classic styles. I probably came closer to buying a 27' Cuttyhunk out in Montauk, than anything, but luckily discoverd a 30' with twin diesels, and that was all it took.

[CharlieZ]

Don,

You've a 30' Cuttyhunk?

Charlie

[Donn]

No Charlie...she's a 30' Eldridge Mcinnis Sedan cruiser.

http://www.imagestation.com/album/?id=4291583433

[CharlieZ]

Don, she's about perfect. What's the burn on those Nissans?

-Charlie

[Donn]

Thanks, Charlie. If by "burn" you mean fuel use, it's 2 1/2 GPH at cruise, 10-12kts @2800rpm. At top speed of 15kts @4000rpm, 4 GPH.

They're SD33's, originally used in the Nissan Scout, and marinized by Chrysler. Straight 6.