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Old 15-09-2013, 17:35   #1
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Whitcraft 45' LRC

I have a 1970s Whitcraft 45'. Technically I guess itís a house boat, but it's been called a Coastal Cruiser, river boat, etc. Back in its day, it was supposedly the only house boat you could water ski behind. LOL. I love the layout and the build quality. I have been living aboard for almost 4 years. Prior to that I lived on a classic 30 ft sailboat.


I would like to pose a question to the group. If you were going to repower this boat for long range cruising, how would you do it? Now before you pass out and hyper-ventilate, let me explain further.

Iím not interested in converting to diesel engines. And I donít want to keep the v-8s. I plan to do the Loop,, the ICW, Bahamas, great lakes, inside passage, sea of cortez, that kind of stuff.


I am thinking I would ditch the twin Chrysler 318s. One doesnít run. The other is unreliable. Instead I would repower with twin 4 stroke outboards---but only 40-60hp each. Basically new twin Honda 50hp. I am not interested in driving the boat on plane, I want to cruise at displacement speed. No idea what that is, but I am guessing 6-8 knots. I want to attach two outboards to brackets on the transom, keep the existing tanks, and use the existing steering/rudder.


I donít know what the hull lines look like below the water. But I have somewhat of an idea of the hull shape(on profile) from an old brochure. I know the boat draws 3í and weighs about 21,000. The hull was a Hatteras mold, Jim Wynne design, but the topsides were a house boat boxy shape. Built by North American Rockwell. I'm guessing its not a full keel all the way aft.


What's the min horsepower I could go? Two engines or one?

Any thoughts would be appreciated.

Thanks
J
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Old 10-11-2013, 13:46   #2
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Re: Whitcraft 45' LRC

Steering around a marina might be a little tricky with one outboard because the outboard prop will be behind the rudder, so the rudders won't work without a bit of speed to get the water flowing over them. Twin engines or a bow thruster could be a good option.

Have a chat to the dealers to see what props are available for a displacement craft because you really need to get this right.

Pete
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Old 10-11-2013, 13:57   #3
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Re: Whitcraft 45' LRC

There are guidelines for power needed for a given weight of vessel.
I don't have them handy, but at 21,000 lbs, I'll guess 25hp.
My suggestion, with no real experience mind you, is to keep the inboard setup,
but just use two much smaller engines. A couple two-cylinder engines would be a whole lot smaller and give you the space back in the engine room.
I am personally looking at building a direct-injected 2-stroke 2-cyl 650cc kawasaki engine as my generator/drive hybrid motor, stock HP was 50hp. But I don't think you need the weight savings, so a four stroke might be better.
Outboards are pretty expensive really. Just some thoughts.
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Old 10-11-2013, 16:08   #4
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Re: Whitcraft 45' LRC

Another thought is using a pair of Mazda rotary engines. They are very compact size.
I'm building one for my jet boat, twin turbo, but you wouldn't need that.

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Old 10-11-2013, 18:19   #5
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Re: Whitcraft 45' LRC

My calculations, and I have no idea what I'm doing, is I need 44hp total. Needs to be two engines, one in each quarter.

I agree with the bowthruster idea. $2,000

Twin 30hp 4 strokes $10,000
or
Twin 25hp 4 strokes $8,000

I don't know that small diesels or even smaller gas inboards would be that cheaper?
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Old 10-11-2013, 23:07   #6
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Re: Whitcraft 45' LRC

New marine inboard engines are also expensive. However, just rebuilding the 318 isn't really a 'marine' operation, so would not be expensive. This is the difference, as outboards are totally marine parts, one can't easily make one from less expensive parts,
whereas inboards can be common engines with marine parts added.

My 650cc jetski engine was essentially free. Rebuilt ones are only $500.
I figure one can carry a complete spare engine (or even two) they are so small and cheap.
My rotary engine really just needs a custom water cooled exhaust, and then a heat exhanger. Atkins sells marine parts for them if you want to write the check.

I saw that you have V-drives, which will take up space inside even if the engine itself is smaller, so maybe the outboards are the best way to go.
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Old 11-11-2013, 07:37   #7
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Re: Whitcraft 45' LRC

Don't think I'd want to be on the Great Lakes or in the Bahamas and underpowered.

Rebuilding the 318s probably least expensive, assuming possible.

Otherwise, replacing with small block Crusaders -- perhaps remans, if you're into that sorta thing -- maybe next level of expense. Especially if your existing gears will bolt up easily. (We're it me needing engine replacements, looking at Great Lakes and Bahamas, I'd prefer new. Your wallet may vary.)

The whole diesel conversion would come with additional issues: genset? feul tanks? weight distribution? gears? shafts? props? And so forth. Start with a $50K boat (for example), spend $100K on the upgrades, and end up with a $51K boat.

If you run the boat at Loop/ICW speeds, fuel consumption won't be bad... and you'll still have room for margin of error when it comes to handling various sea states in bigger water.

-Chris
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Old 11-11-2013, 08:25   #8
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Re: Whitcraft 45' LRC

I concur that rebuilding the 318s would be by far the least expensive route. However, running a pair of outboards is not such a dumb idea but as has already been pointed out the existing rudders would only work when you have some way on so you have flow over them, so you would want the motors to steer. On a boat with that much windage you would probably want a bow thruster.
I recently did 1500 miles of the loop with a 30 x 14 x 7000lb sailing catamaran with no rig driven by a 9.9hp outboard, I actually had two identical motors but only used one at a time, I mention this as one was mounted in the center with remotes and steered along with the rudders,the other was mounted off to one side with no remotes and when that one was run it was locked straight ahead and steering was by rudders only, needless to say all close quarters work was done with the middle one.
One problem with using outboards to push a displacement boat is that there are very few that are geared correctly to swing a large prop to give you the thrust you need, typically they are only in the smaller sizes, my yamahas for example have 2.92:1 gearing vs 2.08:1 for the standard motor so it swings a huge prop, probably bigger than your typical 25hp. I dont know if for example you can buy a true high thrust motor in the hp range you will be looking for, you will also be looking for a extra long 25" shaft.

Steve.
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Old 11-11-2013, 08:40   #9
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Re: Whitcraft 45' LRC

Oh, also not all manufacturers version of a high thrust are created equal, you need to look at the gear ratios and hence the prop size, make no mistake, thrust is what you are after when pushing a big heavy boat with a lot of windage at displacement speeds with low horsepower so look at prop size and the gearing to turn it, numerically higher is really lower gearing which is what is needed to swing a big prop.

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