CAUTION: Metal boat stuff advice sought

Thanks for the pain advice Richard. But I've been dealing with this pain 1999 and have tried everything. The problem isn't as simple as joints wearing out. Both wrists were crushed and after all the bone graftsand reconstructions they just aren't the shape they used to be and the missing cartilage can't be replaced. I do have a couple 3 hp trolling outboards. They are noisy and 2 strokes. I bought a small 4 stroke from Honda before they were available on weedeaters. They are rated at 1 hp. I bought it to make a small trolling motor. Though it worked well it was noisy and the aluminum the motor is made of did not tolerate salt air. In just 1 year the corrosion from living above the beach was severe enough that the clutch housing couldn't be removed. Eric

Reply to
etpm
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blades really be that simple and work well? I mean, can flat blades resembling ping pong paddles really work well? I've read a couple books about propellers, fixed blade types, for boats, and even used the info with a pitch block to change slightly the pitch on a bronze prop in an effort to get it to work better with an antique outboard motor. But if I can get by with flat paddle shapes then it may be possible for me to make a CPP that actually works well. Eric

Reply to
etpm

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They can be but they won't be as efficient. What you can do is to make them curved more like an airfoil. Take a look at a common fan blade for an idea. You will want to make the root thicker though, far more stress in water than air.

Reply to
Steve W.

Hop in your boat and go find this old friend of mine -- he's practically your neighbor. Note the photo labeled, "1970 - Cohasset Harbor, Massachusetts Designed and built a boat with lawn mower engine for power."

I haven't seen Gary in almost 30 years, but unless he's got cranky in his old age, he'll talk your ear off about this stuff and give you lots of practical advice.

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Reply to
Ned Simmons

Gary is not that close to me but I'll contact him and see if he'll see me. I have to drive 70 miles and then take a ferry to Orcas Island. But there is a place called Rosario Resort on Orcas that's nreally nice and I know my wife would love to spend a couple days there. And winter ferry fares are cheaper and reservations are easier to get. I suppose I could take my boat there but it would be over 100 miles and I'd probably be frozen by the time I got there. Eric

Reply to
etpm

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I should have been clearer. A boat prop is cupped. What I'm thinking of is a shape like a foil with the curve equal on both sides of the blade but otherwise flat. Is that correct? Another way to describe it would be a teardrop cross section. So if the blade was horizontal and moving through the water it would have equal lift on both sides? Thanks again Steve for the previous links. Lots of food for thought. Eric

Reply to
etpm

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Teardrop would work but not very well. Now if you make the front side curved but the back side flat or even slightly cupped you would get more thrust. With a CNC or a good template it wouldn't be that difficult to make.

Reply to
Steve W.

SNIP

So I make the part like you describe above, which I can do, but still make the blade resemble a ping pong paddle? Or would it be better to make it look more like a normal prop blade? Since reverse doesn't need to be very effiecent it seems that might work best. I obviously need to do some more reading. Eric

Reply to
etpm

Normal prop blade shape would be better BUT remember that it can change pitch so you don't have to create a profile that works only at one set load/speed like a conventional prop.

Here are some different examples. The last one shows a complicated hub but in the home shop it would be easy to make it simpler.

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Reply to
Steve W.

Stupid question: Why not leave the boat alone (through hull = leaks = that sinking feeling...) and just build a davit hoist at the dock and modify a 4-wheeled hand truck for handling the engine?

You find yourself a really nice 10 HP 4-stroke outboard...

Then either take some steel stock and build a lifting yoke that wraps around the housing and puts a hoisting eye right over the CG. Or you pop open the little plastic plug on top of the engine (or take off the top shroud) and find the factory lifting hole at the balance point, and buy a lifting eye with the right threads.

Oh, and put a second eye on the side of the motor where you can clip on a tag-line rope, with the other end attached to the dock - Just in case the motor takes an unscheduled swim...

Davit hoist on the dock, that's a no-brainer of engineering. But considering the proximity to water, I'd use a 12V winch and a battery box so you just hit the "UP" button when you want to go, and you can trickle charge the battery. Even a solar panel.

120V winches and GFCI's don't get along well, so forget that.

And you take (or make) a 4-wheel dolly with a bracket that looks suspiciously like a transom, drop the motor on it and wheel it off to the garage. Could even have space planned in for a plastic trash can on it for flushing out the motor.

10" pneumatic tire casters if you'll be dealing with grass and dirt, and humongous flotation tires and a "Radio Flyer" steer axle if you have to cross sand.

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Reply to
Bruce L. Bergman (munged human

Greetings Bruce, If only I had a dock. Everywhere I launch the boat is from a ramp. So I need to get the motor on and off while the boat is on the trailer. I suppose I could build some sort of crane on the trailer. Takes the fun out of building an inboard though. And doesn't address the noise. And I would need to get a smokin' deal on a 4 stroke outboard. But at least for now I could use the trailer mounted davit to put the Merc on. Cheers, Eric

Reply to
etpm

You must be at the far end of Whidbey Is, Eric. Or I'm completely wrong and you're not on the island at all. In any case, I'd love to know if you get in touch with Gary. I worked in a boatyard with him in the mid 70's, and built one of his skiffs with his help. Your talk of putting an air cooled 4-stroke in your skiff brought his lawn mower skiff to mind immediately. I was quite surprised to find a photo of it online.

Reply to
Ned Simmons

Greetings Ned, You're correct about me living on Whidbey Is. I'm on the south end, about 3 miles from the ferry dock. So to take the ferry to Orcas Is. I need to drive 60 miles which includes the length of Whidbey, over the Deception Pass bridge, and into Anacortes on Fidalgo Island. If I get in touch with your old friend I'll tell him Ned sent me and I'll tell you about it. Cheers, Eric

Reply to
etpm

Seriously, can't you just leave the motor on the boat and trailer it that way? Maybe make a hoist/engine stand on wheels for removing the engine at home if you need to do maintenance on either the engine or boat? Certainly the blokes with the three 150 H.P. outboards on the back don't take the engines off to trailer the boat and I used to see a lot of "fishing boats" with 5 HP outboards being trailered.

Sure, building a spiffy liquid cooled engine and all the fixins would be fun but I'll bet that either, A. It won't be very serviceable, or B. it will take a lot longer then you estimate to finish it.

I just had a look at small liquid cooled Komatsu diesels - all in the

115 lb. dry weight range. An air cooled engine initially seems lighter but adding water cooling, water cooled manifold (although not strictly necessary) and this and that may raise the weight to about the same as the diesel. An air cooled engine with a water cooled exhaust with an add on pump to supply the water would be the lightest and noisiest. The air cooled engine would also be the hottest but as a liquid cooled engine is running at about 200 deg. (F) it will burn almost as well as the air cooled :-)

Nope, my suggestion is to leave the motor on the boat. If you feel it hangs down too far to trailer then you could fit the sort of retracting engine mount that they use on small sailboats that use outboards for auxiliary power - Richard (cavelamb) can probably describe them if he is reading this thread.

Nope, like the day job, I wouldn't throw the outboard away until I had actually built, tested, rebuilt and made the revisions for the air cooled motor design :-)

-- John B.

Reply to
John B.

Well, there are a few angles to this. Beginning with the boat being rated for a 10-HP outboard, but you can throw all the ratings out the window when you start cutting holes for a shaft stuffing box and through-hull fittings for cooling and return lines, and making an inboard out of it. How are you at TIG Welding to put the engine cradle in?

Any hole in the hull is a potential sinking-at-sea leak, and a homebrew inboard rig has lots of failure modes - and an aluminum hull only magnifies that, the prop gets badly out of balance and you have to keep pressing on towards shore, you'll have fatigue cracks springing up everywhere in the hull...

Even with a life preserver and the typical small-boat survival gear are you in good enough shape to survive an extended stay in the drink? Old Farts in bad shape... Not Sayin', Just Sayin'...

KISS - If you want an inboard, build or buy a hull made for it. This is a Life Safety thing you shouldn't take lightly.

Or go to a local Marine Architect with your plans and drawings and have him sign off that the plan is sound - or engineer a proper solution that won't send your little aluminum skiff to the bottom with all souls on board.

Otherwise I'd go get your dream quiet 4-stroke outboard and leave it mounted on the boat while you trailer it, it should be just fine.

Or put a Davit Hoist on the rear of the trailer, the Harbor Freight

37555 is perfect, just get a longer piece of pipe to weld it to the trailer chassis in the corner. Oh, and spritz the jack cylinder and winch every time with LPS so the rust worms don't get it.

But now that you have the engine off the boat and on a dolly at the Marina, you have to wrestle the engine in and out of the car trunk or truck bed... Why?

If you think that rough dirt roads are going to make the weight of a

10-HP outboard wreck the transom and fall off on the road, add extra bunker rollers/pads at the back of the trailer to support the transom better.

And you can always get bigger cushier tires for the trailer to cut down on the shocks - instead of 4.80X8 tires at 60 PSI you get the 10" wide flotation tires off a Tent Trailer (215-60/8 AKA 18.5-8.50/8) and drop them to 20 PSI. Swap the fenders, and they'll fit.

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Reply to
Bruce L. Bergman (munged human

I put a 4 horse 4 stroke on our 14' jon boat. Trailer has 12" tires. I leave the motor in place and launch off a ramp. I expect it to outlast us.

2 hp would have been fine since we're not going to plane and power past that required for hull speed is wasted. I found the 4 hp lugs and just generates more wake above 1/2 throttle. Everything seems much happier at 1/2 throttle or below. To plane my wife and I would take 15 hp. I don't think a 9.9 would do it. Fuel consumption is miserly. Our other boat is a 22' Pathfinder with a 150 Yamaha down at the coast. Not so miserly.

The jon boat's good points are it's cheap and will take a beating. Bad points are it's not an efficient hull for displacement speeds, and aluminum doesn't absorb vibration. Maybe I'll build a plywood boat some day (different forum).

Be aware that current 4 strokes smaller than 8 hp are single cylinder. Much more vibration than the 3 hp 2 cyl 2 stroke Evinrude I ran 40 years ago.

Pete Keillor

Reply to
Pete Keillor

Add to that (downsides) having a prop and rudder under the boat would mean the boat can't be beached without certain damage.

Reply to
Richard

Good idea, as long as you can lift it off to store inside so it isn't stolen. They are heavy and awkward.

I would consider a lightweight shear leg hoist made from chain link fence rails that rests on the edges of a seat and is controlled by the trailer winch. Get the HF 1/4 ton hoist to lift the motor:

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jack stands tall enough to support the transom when you back the vehicle up to it to lift the motor out.

So far my 1/4 ton hoist has worked well. The only problem has been getting the automatic brake to release after overloading it.

jsw

Reply to
Jim Wilkins

Greetings Bruce, I thought about all the stuff you mention above. The plan is to build the drive as a unit that mounts in the boat so that the hull is stressed where I want it to be. I also though about having the motor and all mounted in a well just in case it does leak. It may be that putting a davit on the trailer so I can remove the motor and lay it in the boat is the best way. I have tried leaving the motor attached to the transom. Once. By the time I got home the transom was already damaged. The trailer really does bounce around. So now all I need to do is find a good deal on a 4 stroke outboard and get rid of the Merc. Eric

Reply to
etpm

There's the solution! Put a Transom Saver on the trailer to transfer the weight of the motor to the trailer, and put fat flotation tires on the trailer so you can lower the pressure and make them cushier.

You don't have to take the motor on or off every time you want to use it, and the boat will last a whole lot longer even when you tow it on rough dirt roads.

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Reply to
Bruce L. Bergman (munged human

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