The quest for the inexpensive small inboard with reverse

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  • merlinron
    Senior Member
    • Aug 2005
    • 978

    #31
    upscale models, i don't know about that, my hydro unit came out of 15 year old craftsman( crapsman) 11 hp. rider.just about the lowest scale rider you can buy.most all of even the lower power riders could be had in hydro or ger drive, so it's just a choice, there.becuse of the inclination of the drive, i would think a hydro unit would eliminate the possibilities of lubrication problems. the hydro differential is about the same size as a football, with the axle housings hanging off each side. elimination of one axle housing makes it about 18 inches long total, 12 of that being the axle housing that woud be in line with the prop shaft. that's not too big, i would think. i don't think orientation would be a problem, most marine drives aren't much more that 15 degrees inclined, i have almost a half acre of my yard on slightly more slope than that and i never had a problem with the hydrounit starving out.
    most riders do have bigger moters, granted, but it's not for moving the mower, that doesn't take a bunch of power, the bigger motor is for swinging the blades.the hydro unit doesn't know how big a motor it's attatched to, it just changes the direction of whatever torque is applied to it at whatever reduction ratio is designed into the hydraulic transfer.
    setting it up for a sail drive would simply mean changing the axle orientation from being at right angle to the drive belt line (as it is in a riding mower) to being in line (or parallel) to the belt drive line.
    eliminating one axle side would allow the drive unit to be moved closer, by the length of eliminated axle, to the power source, using shorter belts. with the axle eliminated, the power source (a verticle shaft lawnmower motor of any hp. rating chosen) could be lowered in front of the drive unit and a jack shaft could be inserted between the hydro unit and the power source to transfer the belt drive back up to the top of the unit..... the pto on the motor is on the bottom.... belt to bottom pully on jack shaft,positioned verticaly, between motor and hydro unit... belt from top pully of jack shaft to input shaft/pully on hydro unit. the entire drive unit could be fastened to a fabricated frame of angle and plate that positions the motor, jack shaft and hydrounit in the proper location to each other, then mounted to bed rails in the boat. i would think entire unit wouldn't be any bulkier than any other drive beng concocted here. the length of the axle housing can't be included in the overall size of the drive unit, because it is in line with the prop shaft and only would take up some of the space of a normal prop shaft, the shaft being shorter by the length of the axle housing.

    Comment

    • geeman
      Senior Member
      • May 2003
      • 5522

      #32
      We're so caught up on what is "boaty" we dont take a close look at what can be done.A motor set up like that could be run all day long high rpm, tractor motors like high rpm's btw.on a couple of gal's of gas.Not just sail boats,but about any reasonable size boat.Parts are easy to get,and not expensive,,,,,,

      Comment

      • Cuyahoga Chuck
        # 7727
        • Dec 2003
        • 12984

        #33
        "The quest for the inexpensive small inboard with reverse "
        This is where we started and I think we are hung up on what "inexpensive" means.
        A small 1960's era outboard with enough refurbishing to keep it reliable could easily fit into my "inexpensive" catagory. But, I doubt that many of the suggestions made here could come within $500 of said outboard even if you left out the reversing requirement. If the inboard setup required any amount of professional welding and machining the price could soar.
        American ingenuity could , probably, produce everything that was mentioned here. It's when you put a pricetag on it that things start going to hell.
        I wish Mike luck but, I think he is going to have his hands full for a while and I think the idea of doing it on the cheap will take some readjusting.

        Charlie

        Comment

        • merlinron
          Senior Member
          • Aug 2005
          • 978

          #34
          "on the cheap" in relation to what a small commercial inboard drive costs would be pretty easy to do, i think that's the criteria, here. i don't think i'll have anywhere near 500 bucks in a drive like i described. everything but the prop, shaft and stuffing box is readily available at any big box store, mild steel angle and plate is dirt cheap from a salvage yard, hydros can be had from bone yards for 20 bucks and i see small push mowers for sale all over for 25-50 bucks. i guarantee you i could put this together with no machine work beyond a shaft cut to fit the prop to. it could be done without even welding anything if you wanted to. the sahft ,prop and stuffing box might put me in that 500 dollar range, i'll admit... i don't know what that stuff goes for, but it wiil still look better than a 500 dollar outboard hanging off my classic boat.

          Comment

          • paladin
            Senior Senior Member
            • Dec 2000
            • 26476

            #35
            re the above comment on the size of electric motors.....I just tossed a motor 5 1/2 inches in diameter and 11 inches long rated at 10 hp at 24 volts........it was a starter motor modified for use with a gatling gun.......so they can be small.....
            Transmissions.....think chevy cogged belt drive....will give reduction when the proper pulleys are chosen, also the timing belts for the small 4 banger chevies.....they are strong enough to use with a 225 hp six cylinder buick V6 modified for aircraft use...
            mufflers...ain't difficult to make your own, think silencer for 50 cal machine gun....as designed and invented by Hiram Percy Maxim....can be made from stock stainless pipe, and bronze wool packing...put a water jacket on the outside for additional cooling...rig it to a bilge pump for water when the air cooled engine is running...youse guys gott move to china or thailand to see some real innovations..
            Wakan Tanka Kici Un
            ..a bad day sailing is a heckuva lot better than the best day at work.....
            Fighting Illegal immigration since 1492....
            Live your life so that whenever you lose, you're ahead."
            "If you live life right, death is a joke as far as fear is concerned."

            Comment

            • merlinron
              Senior Member
              • Aug 2005
              • 978

              #36
              yup, if a guy's wprried about slippage with a v-belt, the cog belt's the way to go. only problem with them is that the pullies don't come cheap. they sure can handle the horsepower though. subaru aircraft conversions use cog belts also.... reliable, less friction and heat. essentially, chain could also be used, but would require some guard fabbing to keep lubrication from contaminating everything. chain might be a little less maintenance criticle(?)... maybe chain on the bottom drive (harder to get at, less likely to be inspected) and belt on top for ease of tweeking final hydro drive speed.
              i jiust looked at my hydro unit, it's 19.5" outside axle housing to ouside axle housing, with about 4.5" of 3/4" dia. axle stub extending from the ends.one could easily eliminat about 4-5 " of axle housing on one side. the othe side is longer( 10") and about 1.75" in diameter, which would be pointed at the stuffing box, in place of the prop shaft. the end of the axle is just a shoulder with a 3/8" threaded hole for the bolt that holds the wheel hub on. this would easily accept a commonly available flange-type rubber flex coupler that any bearing house would be able to get, they probably would show up in a granger catalog, also.
              if, by chance you can't get the hydro unit's final rpm. up to good prop speeds, you could overdrive the prop shaft with another belt drive at the axle. this might allow you to keep the hydro unit inside it's normal operating rpm range,wear and tear wise. there is quite a reduction there... (between input shaft rpm. and axle rpm)..., it probably would still have enough power after overdrive to be efficient enough at the prop.
              so far this is all just ideas, but i'm getting more interested....i have to look into these hydrostatic drives by manufacturer's specs and find what rpm range they are supposed to be run at.
              paladin,
              you wouldn't need to rig an electric pump for cooling water. any small gas engine can be tapped for a tillotson type pulse fuel pump. the go-karts racers do it all the time when they run their 5hp briggs class engines on alchohol with a tillotson carb, they use secondary compression from the crankcase to run the pump.
              as for muffling, most of the small engines are actually pretty quiet as soon as you put any length of exhaust pipe on them and get the exhaust pulses organized, as you would routing the exhaust out of a boat's motor well.
              china and thialand... yup... the macgivers of the world.

              Comment

              • Excalibur
                older than my boat
                • Sep 2006
                • 295

                #37
                Originally posted by Cuyahoga Chuck
                Open,
                No engineer here but, I think you are creating energy out of thin air.
                A 5 HP gas motor puts out only as much torque as a 1¼ HP electric motor. You couldn't run your generator with a 1¼ HP electric motor and expect it to simultaneously make enough juice to run a 2HP electric motor.
                I would think with the expected energy losses from the various conversions involved you would have to start out with a gas motor of 10 HP to generate enough juice to run the 2HP electric motor.
                The math to proove this point is beyond me but, I know from past experience that an electrically driven air compressor needs a gas motor that is rated at 4 times more HP to provide the same torque as the original electric.

                Charlie

                Chuck, I'm not certain where your math is going, but race car battery chargers run by lawnmower engines are a pretty common sight around racetracks. An article on building one can be found here:

                Emergency Power: How to build a generator using a horizontal shaft engine from an old lawn mower/edger. Do it yourself generator tips.


                I'm certain there are others. Also, modern auto alternators usually have rectification and regulation built in, so they are really putting out full wave DC, not AC. You just need a battery (a motorcycle battery will do), to smooth out the waveform. According to Honda, their 2500 watt genset (that is what we are bulding here, of course), uses a 5.5 hp engine. 2500 watts of power ( 208 amps at 12 volts) will drive any most high thrust trolling motor on the market and get that little 15 footer moving.
                Thurman

                Comment

                • alkorn
                  Senior Member
                  • Jun 2006
                  • 504

                  #38
                  Go-Cart Reversing Gearbox

                  Hoffco-Comet http://www.hoffcocomet.com/comet/index.asp makes a small reversing gearbox for use on gocarts. I don't know what it costs, but I assume it must be fairly cheap. They don't show it on their website, but I heard about it and inquired. They sent me a PDF file which I've posted to http://www.filebox.vt.edu/users/alkorn/FNR.pdf .

                  I've thought about using this with a small air-cooled engine as an inboard drive. I think it would work. I don't know how long-lived it would be. Go-carts don't run many hours compared to boats, but then again there is a lot more shock loading in driving a wheeled vehicle than in turning a prop.
                  I will beg you for advice, your reply will be concise, and I will listen very nicely and then go out and do exactly what I want! (Apologies to Lerner and Lowe.)

                  Comment

                  • brian.cunningham
                    Multihuller
                    • Jan 2002
                    • 2451

                    #39
                    Well, feathering props are great on sailboats.

                    Why not find one that can be 'reverse feathered' if you catch my drift.
                    Then you can skip the gearbox.
                    Brian T. Cunningham
                    SWIFTWOOD - my schooner rigged trimaran sailing kayak
                    http://members.aol.com/swiftwood/

                    Comment

                    • Cuyahoga Chuck
                      # 7727
                      • Dec 2003
                      • 12984

                      #40
                      Ex,
                      Charging a battery is done at a low amperage so not much HP is required. And it's much different than running a gas motor to drive a generator that supposed to power the electric motor that drives the screw. That's where this thread was going when I made that comment way back when.
                      In general, present day electric drives are hostage to heavy batteries. The longer the cruising range desired the bigger the array of batteries that have to be installed. And if you discharge a battery array too severely it takes a lot of time to bring it back. There are some new electric drives on the horizon that have improved motors and improved batteries but they are wildly expensive.
                      So, electric drives are available for those who can afford them and those that are not in a hurry. Most electric drives have to be kept at 50% power or so if you expect to cover any distance and have enough juice to get home.

                      Comment

                      • leaotis
                        JuniorJunior Member
                        • Apr 2004
                        • 666

                        #41
                        I found a very small 4.5hp water-cooled ATV engine on a Chinese website. My excitement was short lived when I saw that it idled at 4,000 rpm.

                        Air cooled engines can be made quiet but only ones with overhead valves.
                        =~=~=~=~=~=~=~=~=~

                        When we remember we are all mad, the mysteries disappear and life stands explained.

                        Mark Twain

                        Comment

                        • stef
                          Member
                          • Sep 2001
                          • 83

                          #42
                          It looks like a pretty basic transmission. Any cost guesses?

                          Combine in with a honda 4-stoke with a reduction gear 6:1 (I think this is a standard ratio off the shelf that is). Swinging a real sized prop on a displacement hull should be expected.

                          Best regards,

                          Stefan.

                          Comment

                          • Cuyahoga Chuck
                            # 7727
                            • Dec 2003
                            • 12984

                            #43
                            Originally posted by leaotis
                            Air cooled engines can be made quiet but only ones with overhead valves.
                            This is a distinction that doesn't seem rational to me. Without a water jacket there is nothing to soak up the noise and all aircooled motors need a fan which also produces noise. And, if you try to operate a fan cooled motor at low RPM's to keep the noise down the motor could overheat because the fan isn't processing enough air.
                            Whether the valve stems point up or down doesn't seem to be much of a distinction in terms of DB output.

                            Comment

                            • Ron Carter
                              Senior Member
                              • Aug 2004
                              • 743

                              #44
                              [quote=merlinron;1337254]" the sahft ,prop and stuffing box might put me in that 500 dollar range,quote]

                              My experience is if you can't find the above used you will have well over $500 in the three before you even buy a shaft coupling much less the other components. Propellors for low hp applications that don't turn at outboard speeds are almost impossible to find unless ordered new. Seroiusly spendy in that case.
                              If you don't know where you're going, you might not end up there.-Yogi Berra

                              Comment

                              • zenda
                                Senior Member
                                • Aug 2005
                                • 155

                                #45
                                Originally posted by paladin
                                re the above comment on the size of electric motors.....I just tossed a motor 5 1/2 inches in diameter and 11 inches long rated at 10 hp at 24 volts........it was a starter motor modified for use with a gatling gun.......so they can be small.....
                                Transmissions.....think chevy cogged belt drive....will give reduction when the proper pulleys are chosen, also the timing belts for the small 4 banger chevies.....they are strong enough to use with a 225 hp six cylinder buick V6 modified for aircraft use...
                                mufflers...ain't difficult to make your own, think silencer for 50 cal machine gun....as designed and invented by Hiram Percy Maxim....can be made from stock stainless pipe, and bronze wool packing...put a water jacket on the outside for additional cooling...rig it to a bilge pump for water when the air cooled engine is running...youse guys gott move to china or thailand to see some real innovations..
                                Paladin,
                                You're the man!
                                “It ain’t what ya don’t know that hurts ya.
                                What really puts a hurtin’ on ya is what
                                ya knows for sure, that just ain’t so.”
                                Uncle Remus

                                Comment

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