Total Newbi Question

[Rake]

I am wanting to build a 20-30ft open cruiser type boat. I would like to use an automotive motor to simplyfy and reduce cost over the use of an outboard motor.

Do I need to use a marine leg? Tranny?

I can fiure out the boat construction from plans, books, and this fine forum. But the motor problem has me baffeled!

[Bob Smalser]

If you really meant "total newbee"...you might consider building something smaller powered by oars, first....and make your mistakes there.

But yes, as a kid we used flathead 4 and 6 auto engines in work boats...raw water cooled and dry stack to overcome marinization issues inexpensively...and those engines didn't last very long.

I'd guess these days that marinizing a junkyard rebuild or crate motor with heat exchanger to use antifreeze and wet exhaust might cost more than shelling out for a rebuilt marine engine....not to mention the maintenance access issues of an engine not designed for tight boat applications.

And a lot of powerboat do-it-yourselfers live here:

http://boatdesign.net/forums/forumdisplay.php?s=&forumid=11

[Jack Heinlen]

Second Bob's a small skiff or sumpthin, before you tackle this.

Lots to figure out in a power skiff the size you say. Doable, but bite in small pieces.

OTOH some people larn really fast, so who are we to say?

"A man's reach should exceed his grasp, else what is heaven for?"

[Bruce Hooke]

I believe WoodenBoat ran an article a few years ago on converting an automotive engine to marine use. As I recall, it was quite an involved process to really end up with a safe and reliable engine suitable for marine use.

In any case, if you are interested in pursuing the idea you might want to dig up that article.

However, do you really mean that you want to substitute an auto engine for an OUTboard? If so, I assume you plan to install the converted auto engine as an inboard, no? If so, I would be very surprised if you could do it for less than the cost of a used outboard, and installing and maintaining an inboard is almost certainly going to be much more complicated than an outboard. That's not to say that there are not lots of good reasons for using an inboard engine, I just do not think that cost and simplicity are two of them.

[cbob]

Rake,
I would have to agree with the previous responses, however aside from the weight issues, there have been some B minus movies filmed in Bancok, Thailand, I think, where small speed boats full of desparados are blasting around the canals with stinger engines. A smaller four cylinder auto engine mounted balanced somehow, over the transom, with a propeller on the end of apparantly unsupported shafting, directly driving,and by lowering the front of the engine, the prop and shaft are hinged up out of the water. The overall length of this arrangement makes this a speed boat of overall length maybe 150 % more than with more conventional drives. This is no Hollywood trickery as I have seen one of these zooming up the Sacramento (California) River from about 20 yards away. That propeller spinning 50 to 150 H.P. 10 feet astern looks really scary, particularly when transiting areas of the river reserved for young swimmers. Check first with the U.S.C.G. (if you can find anyone who knows what you'r asking) and see if such an arrangement is legal.
Happy Speeding, cbob

[Rake]

Thanks to everyone for their suggestions and advice. I think I might just skip the auto motor idea.

The plan is to start to slowly build the motor boat, while at the same time woking on smaller craft. Such as canoes, kyaks, and skifs.

[L.W. Baxter]

"A man's reach should exceed his grasp, else what is heaven for?"[/QB][/QUOTE]

I wonder if heaven is where all those unfinished boat hulls go? I was at a farm auction this weekend and they were giving away a bare hull, what appeared to be a 30' by 10' fiberglass sailboat, ordered during the '80's, which had sat in this guys field for about twenty years, long enough for the trailer it sat on to rust beyond all recognition. The guy had feebly attached a couple of "gunnels", circa 1986, then I guess he got tired!

There were no takers on the "free" boat, by the way...

[Nora Lee]

Garveys race in organized fashion, along the NJ coast.

Went to see races as far back as 1962. I am sure that in the past 40 some years, it has been refined. Perhaps someone in this forum has some experience.

Regards,

Nora Lee

[Aramas]

I've seen raw water cooled/dry stack car motors used in launches for decades without problems. Some still had the original 3 speed/reverse gearboxes smile.gif However, they were old, slow revving, heavy british engines.

As a teenager I ran a 17' ski boat with a marinised but raw water cooled 350 chev. It was kept on a mooring and used nearly every day for around nine months of the year. By the end of the season it always crapped itself catastrophically - usually involving internal parts exiting through the side of the block :rolleyes: Modern engines with alloy heads and suchlike must have heat exchangers and anti galvanic water conditioners, or they would be unlikely to see a month out.

The cheapest/cleanest installation would be a second hand 4 stroke outboard in a well. A secondhand marine diesel might cost a little more, but is worth it.

I kind of like yulohs ;)

[Bob Smalser]

By the end of the season it always crapped itself catastrophically - usually involving internal parts exiting through the side of the block.... Didn't mention above that I've seen more than one fire caused by those old flatheads when they went south.

The waterjacket webbing in the block is thin enuf to rust thru eventually....and when it does, seawater enters the combustion chamber and ya eventually get a hydraulic failure when the piston tries to compress more and more water....usually throws a rod out the side of the block...and if it happens gradually enuf to break the rings first, then enuf gasoline can get into the oil to have large flames spit outta the hole the rod made in the block.

Always good for that adrenaline rush.