The quest for the inexpensive small inboard with reverse

[mike hanyi]

I hope this shows some interest.
some years ago I purchased a small double ended traditional finnish boat type called a fiskari (fishermans boat) it is about 15 ft and maybe 5 ft wide, it is more or less a double ended rowboat with an inboard rudder and engine. engine being a B&G 5hp, directly hooked to the propshaft. now soon I will start its rebuild. over the time I started to appreciate the simple and inexpencive nature of this honest boat, its light enough for 2 people to pick it up and move it.the motor is more used for doing longer distances and is maneuvered under oar as there is no way to go slow with the motor.

which brings me to the idea of a cheap transmission for small aircooled engines.

Engine canadates are Honda, B&G, also are small aircooled diesels that seem to be now affordable.
there is no watercooled 5hps out there as there is no demand for them.

The Idea
cheap reversing transmission for small motors.

I will try to work on the concept of the motor mounted on a hinge,
there may be some kind of spring to lift the hinge slightly
the motor is equipped with standard pulley, and a wide collar,
directly under the pulley is another pulley which is on the propshaft, on one of the shafts is also a hard rubber tyre, the other shaft should have a smooth metal wheel to make contact with the tyre when the hinged motor is lowered.

how does it work?
some kind of hand lever lifts the motor and puts tension on the belt=forward
release the lever and the motor sits on the short springs=neutral
no tension on the belt
pressure is applied to the lever and the springs are compressed, the hard rubber tyre is now pressed against the metel wheel=reverse.

this whole idea should be able to be made easily, except for the pulleys,
there will need to be a thrust bearing in a bearing housing, the type that is self aligning, so that alignment between the motor and the prop shaft is no so critical.

also I have seen model airplane propellers used sucessfully on low powered electric motors, it would be easy to use this idea, cheap propellers that come is lots of pitches and sizes.

I am really interested in making several kits for a production run of these cheap simple boats. feedback on this concept would be great.
remember this is to be a cheap plan and not over engineered.

mike

[Canoeyawl]

http://www.robbwhite.com/rescue.minor.machinery.html

[Thorne]

Wasn't there a recent thread here about some small German diesel marine engine - probably worth a search.

[RonW]

I understand simply, cheap, readily available. BUT....

But on the other hand a 5 hp air cooled briggs and straton is the noisiest thing available to the public. Are you going to wear ear plugs.
Then also there is the vibration, and fumes.
Personally I wouldn't care if it got 199 miles to the gallon and only cost a total out lay of $150. to set up.

Sorry to be negative, but some things are not worth it.
A little quiet time on your boat is worth a few xtra dollars.

[Tom Robb]

How about the transmission from one of Europe's very small cars?
I'd think that the less "Mickey Mouse" the better, and why reinvent the wheel as it were?
But, the boat had no transmission originally. Should you ask yourself why you need one?

[Thorne]

From what I've heard, forget the aircooled option unless you are (or wish to become) deaf.

For a different motor, and/or possibly a transmission to fit, try this site, click on the Engines link on the left -

http://boatdiesel.com

Vetus and several others have old models listed that are 5hp, Thornycroft has an 11, Volvo has a current 10hp model in production. This was just with a quick look at various manufacturers on this site.

Also, somewhere on the web I've seen pics of a metal shield / housing that can be rotated around the prop to block the propulsion -- not a true reverse but does generate some backward thrust, and allows you to stop forward thrust without killing the motor.

[Stu Fyfe]

http://www.farymann.de/frames_englisch.htm

One of the few small diesel makers left. I've had two of them 5 1/2 HP and 9 HP. Reliable and easy to work on.

[Cuyahoga Chuck]

Most small motors have a powerband that is too high in the RPM range to drive a propeller efficiently. They need a gear reduction. That's why your boat was always trying to go so fast. Unfortunately, a suitable gear reduction box can be quite expensive (worth more than your motor) and a little hard to find and a little hard to install.
The motor/transmission setup is ideal because it can be compact and most of the rotating components are safely away from the passengers.
So whatever you create will have to compete with the traditional motor/ transmission. If it requires too much space and endangers the boaters no one will want it.
Airplane propellers are designed to operate in air which has different dynamics that water. While they may push the boat I doubt they will be as efficient as a boat propeller.

[mike hanyi]

thank you canoeyawl- you were the only good answer out there,
on the comment of "just buy a ferryman" we are talking the difference of 500 dollars verses 3500 dollars,
remember I wanted to come up with a cheap setup

Its the transmission I am interested in, people can choose whatever engine they like, about the reduction its pretty streight forward to use the pulleys as the reduction.
If only I could get a picture of the robb white transmission??

mike

[Bradley Stemen]

A small, lightweight transmission can be found at

www.olympicgear.com

These 3 speed w/reverse transmissions have been around for over 50 years, used in riding tractors, Crosley autos, factory/airport material handling vehicles, they are bulletproof and are still being made. Find a used one out of a riding mower or Crosley auto and the rebuild parts (if needed) can be had through Olympic Gear.

Brad

[openboater]

Aircooled engines can be made very very quiet.

Just look and listen to the Honda EU series of generator, These are so quiet....... Look at the technology used in the EU series for quietness.

[Rick Starr]

The Snapper concept is incredibly simple and works pretty well, and I have always wondered if there was a marine application for it.



It might need a vertical shaft motor, but that might carry hidden blessings in terms of mounting and removal. More about Snapper mowers on the web, principally here:

http://www.snapper.com/rear_engine_riders.html

[mike hanyi]

thanks people- I started doing some hunting for the troybilt setup- If someone knows an exact location many thanks, the snapper idea is worth looking at also, as the world is just full of used lawnmower motors, if people only changed the oil every year B&G,s would last forever.

mike

[P.I. Stazzer-Newt]

The infinte improbability drive.

[Paul Pless]

Have you visited this sight?

http://www.oldmarineengine.com/index.html

[Philip Maynard]

I have a direct drive 5HP in a 15'-8" sailboat. It is not quiet but I would not call it real loud either but I would like to find a better muffler for it, I am using a small tractor muffler but that really was not much better than a small B&S muffler I originally purchased for it. Once I adjusted the governor it has a little wider speed range, I naturally would like reverse but would not think the increase in complexity is worth it. The EU generators are not very helpfull in terms of adapting what they are doing for general aircooled engines - I see they are "totally enclosed" which must help make them quiet because I think a surprising amount of the noise is mechanical - does anyone know of a quiet in-line muffler with say 1/2 to 3/4" fittings for 5HP?

[openboater]

a nice little write up of various propulsion systems. Maybe something here will help the creative juices flow

http://www.dieselduck.ca/machinery_p...ion_layout.htm


I thing one of the easiest is a small gas motor running a large alternator that then converts to DC that runs an electric motor to tun the prop. easy to make go forward and backward and run at different speeds, something a mechanical setup has problems with.

Or possibly a combination system, the 5hp gas for forward, and a cheap trolling motor for maneuvering around the dock. But your oars are cheaper.

[Cuyahoga Chuck]

"a small gas motor running a large alternator that then converts to DC that runs an electric motor to turn the prop"

Easy? In the confines of a 15' sailboat? It would certainly do away with any need for ballast.

[PeterSibley]

I have a direct drive 5HP in a 15'-8" sailboat. It is not quiet but I would not call it real loud either but I would like to find a better muffler for it, I am using a small tractor muffler but that really was not much better than a small B&S muffler I originally purchased for it. Once I adjusted the governor it has a little wider speed range, I naturally would like reverse but would not think the increase in complexity is worth it. The EU generators are not very helpfull in terms of adapting what they are doing for general aircooled engines - I see they are "totally enclosed" which must help make them quiet because I think a surprising amount of the noise is mechanical - does anyone know of a quiet in-line muffler with say 1/2 to 3/4" fittings for 5HP?

I'm not sure how you would go fitting it ,but you might find the muffler from a small Japanese motorcycle useful..the road bikes , Honda etc ,are very quiet .

[openboater]

Chuck, I think you might find it smaller than you think. The motor alternator can be put anywhere in the boat,just run cables from alternator to motor. and since he already has a 5hp in the boat, that part of the package is the same with the addidtion of a 100 amp truck / car alternator. when I said large I meant in output not size. Simple rectifier to go from ac to dc.

The electric motor of 2 hp is about the size of a 1 gallon jug. that mates up to the prop shaft with a small and easy to build reduction belt drive. forward nuetral and reverse consists of a switch. gas motor is measured in peaking hp and electric is measured in continous, that's why a smaller electric is the same as a larger gas.

it's just that sometimes you can make things simpler by making things seem more complex, but really they are simpler.

making all these mechanical gizmo's plus a clutch, and forward neutral and reverse with belts, somebody's gonna start loosing fingers and toes if they aren't careful.

[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

[geeman]

How about possibly a 12 hp B&S lawn tractor motor.More power,your transmission is there(reduced) maybe drop the exhuast in the water ?I've heard its being done.Change the gearing in the tranny to get the prop speed closer to what you want?Just thinking out loud here.The biggest problem I see here would be closing in the air cooled motor too much to suppress noise and smothering the engine to where it cant get enough cool air.With this set up you also get a charging system for running electronics.

[mcdenny]

I've done a lot of web searching for a small marine motor and have not been able to find anything "marine" other than expensive yanmar diesel engines.

There is no more economical marine drive than an outboard motor for lower horsepower needs. The trick is packaging it so it doesn't spoil the looks of a traditional boat. Maybe you could mount a short shaft engine is a well and perhaps still steer with the rudder. A lot of extra space is needed to accomodate the tilting function but if you were happy with the inboard maybe you could forgo the tilt feature.

A brand new 8hp Yamaha 4 stroke OB is only $1500. 5 hp Tohatsu is $1100. What, maybe 10 minutes of labor to install? Works good and easy to resell if you change your mind. Hard to beat that.

[George Ray]

Look at the scooter market.
Several SMALL fluid cooled engines with transmissions.

Honda =>Rukus:
Aprilia => ?models?:

The aprilia engine is apparently very sopisticated but I can't speak to any details.
***************

[Paul G.]

It all depends on how far you want to go.
This bloke converted an outboard into a saildrive by shortening the leg and making a mounting plate. The boat is 13 feet long. I have seen it in the flesh and if I could've I would've!

[Jay Greer]

There are two tiny two cylinder two cycle marine engines on the market. The "Vire" built in Finland and the Dolphin, made in England.
Both engines weigh about 120 lbs, including the reverse gear and put out 12hp. I have installed the Vire in one Danish double ender and it is more than adequite to power the little 23 footer. How ever, the engine has an aluminum manifold that requires a heat exchanger in order to prevent electrolosys. My prefrence would be for the English Dolfin as it is built of cast iron.
http://www.fairwaysmarine.com/vire/index.asp
http://www.dolphinengines.co.uk/
JG

[merlinron]

what about the hydrostatic drives that are used in riding lawn mowers. has anyone ever tried one?
they all have infinite speed, neutral and reverse. most have a fan built onto them for cooling and i would think they would work with electric or int. combustion power sources.
possibly, they might be a bit slow at the axle, but some of that can be sped up with a different size pulley on the input shaft and on the motor. the guys that race riding mowers speed up the living daylights out of them and they don't have any problems with them. i do know that they replace the standard oil with synthetic because of heat break down from the mineral based oils normally used. that, and small horizontal honda from a push mower might make an easily built, quiet drive for a small sailboat or launch.
i have been thinking of looking into that for my boat, i already have the hydro unit. i just don't know if i want all the drag from the prop being in the water all the time, vrs using a trolling motor. if a guy could get a small folding prop, that didn't cost an arm and a leg, i think it would be ideal, at least for my purpose of just getting to and away from the dock.
if you wanted to get really fancy, you could remove the unused side of the drive axle at the differential, cut/machine the corresponding axle housing off and cap it. with that removed, you could mount the motor lower in front of the hydro unit and jack-shaft the belt drive back up to the top of the hydro unit, where the input shaft usually is.
there are also horizontal input shaft types, from club cadet shaft drive riders, these actually have the axles housing bolted to the differential, which would make removing the unused axle and capping the dififferential a snap. you could then use a horizontal output power source and make i neat compact drive unit.
this could actually be done with any of the gear drive differentials from older riding mowers as well..... there's tons of both types laying around in junk yards.

[merlinron]

i just thought of another way....
there are snowmobiles that have tiny reversing gear boxes, with a neutral station as well. snowmobile drive systems are pretty highly stressed,pretty much, constant drag, expotential to speed. i would think one of these might be rugged enough able to survive a marine application. could be used direct drive, in-line with the motor and the prop shaft.

[Cuyahoga Chuck]

Most of the tractors that feature hydrostatic drive are the upscale moderls which feature fairly large motors. Even if it would work it would not be cheap.
I have an old 11HP lawn tractor with 5 forward and one reverse speed. They can probably be had quite cheaply but, I wouldn't call it very compact. It has an axle coming out of each end of the transmission. And there is a question of proper lubrication if the unit had tobe oriented differently than it was in the tractor.

[geeman]

No need to change the engine orientation,move the tranny closer to the motor pully using a smaller belt I think the tranny wouldnt be a problem.I've got a 12 hp tractor motor in my shop I've been experimenting with along the lines you are talking about.I believe the tractor motor concept is very doable.It sounds weird because we tend to think in conventional terms.We need to start thinking outside the box now days .Remember ,no alternator needed with that set up too.

[merlinron]

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.

[geeman]

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,,,,,,

[Cuyahoga Chuck]

"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

[merlinron]

"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.

[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..