Inboard outboard air cooled engine

[Lone Duck]

Re: Inboard outboard air cooled engine

Yes! That engine will idle down to 800 rpm and if in good shape even lower. say 600 rpm. But you may get a hiccup if you accelerate to quick.

 

[DJ]

Re: Inboard outboard air cooled engine

Yes! That engine will idle down to 800 rpm and if in good shape even lower. say 600 rpm. But you may get a hiccup if you accelerate to quick.

That's doable. You just need to figure out a way to make the shift rod actuate, from the helm. It shouldn't be that hard. A little bracketry and an old two lever OMC shift helm and you're in biz.

Now that I think more about it, any single lever helm (two cable) should work.

 

[Kenneth Brown]

Re: Inboard outboard air cooled engine

I missed this the first time around and I love it. I saw a boat at a horse auction once that had a horizontal shaft 5 hp Briggs on it. It was connected to the drive unit from a jet ski all in the bottom of a 14 ft aluminum flat bottom. Never got to see it work but it looked very cool.

 

[maxum247]

Re: Inboard outboard air cooled engine

How about a suicide shift like some of the old Harley's used? If I could come across some sort of floor mounted shift lever like the old pickups used to use this would be a simple install, rock it back and forth, simple and sweet!

 

[tashasdaddy]

Re: Inboard outboard air cooled engine

the old chris crafts just had a lever in the deck, 3 positions f n r. the throttle was in the center of the wheel.

 

[maxum247]

Re: Inboard outboard air cooled engine

If I use a belt and pulley system to run the lower unit would I get less viberation than hooking up shaft to shaft with a wire reinforced hose connection between the motor shaft and the lower unit shaft? If I put a larger pulley on the motor and a smaller pulley on the lower unit will this speed up the turns on the unit? Any down side to using this system?
THANKS!

 

[MikDee]

Re: Inboard outboard air cooled engine

If I use a belt and pulley system to run the lower unit would I get less viberation than hooking up shaft to shaft with a wire reinforced hose connection between the motor shaft and the lower unit shaft? If I put a larger pulley on the motor and a smaller pulley on the lower unit will this speed up the turns on the unit? Any down side to using this system?
THANKS!

IMO, Usually you need a shaft pulley 3 times bigger then the motor pulley, to get the right amount of torque (at least on a go kart anyway) so as not to lug the motor too much, but you may have a problem with the belt slipping on a pulley system like this, unless you put on a tension held idler pulley. between them.

 

[maxum247]

Re: Inboard outboard air cooled engine

Thanks, thinking that if I were to hit anything with the lower unit being mounted under the boat that the belt, pulley system would let the prop stop and the belt would slip on the pulley. Maybe avoiding damage, and hopefully cutting down on viberation and gaining a little speed at the same time!

 

[MikDee]

Re: Inboard outboard air cooled engine

Thanks, thinking that if I were to hit anything with the lower unit being mounted under the boat that the belt, pulley system would let the prop stop and the belt would slip on the pulley. Maybe avoiding damage, and hopefully cutting down on viberation and gaining a little speed at the same time!

Your prop hub is supposed to absorb shocks. By the way, I don't know, nor do I think anyone here can tell you what, if any, gear reduction, or gear increase, as you might be thinking, is needed to drive that prop. Outboards usually have 2:0X1 gear reduction in the lower unit, so direct drive off the motor would probably be the best option. All you need is a good flexible coupler, maybe with a heavy rubber insert to absorb the shock, & vibration, or even maybe just a mechanical centrifugal clutch, like a go-kart?

 

[MikDee]

Re: Inboard outboard air cooled engine

What size shafts do you have on the motor, & lower unit? 5/8", 3/4", 7/8"?
I found a link to some couplings, in fact there is a "Lovejoy" coupling there. They seem like just the ticket, at a reasonable price, Here you go:
http://www.northerntool.com/webapp/wcs/stores/servlet/category_6970_96+1501[url]

 

[maxum247]

Re: Inboard outboard air cooled engine

Hey MikDee, thanks for the link! Motor shaft size is 1 in., the lower unit shaft is 9/16 in. as best as I can tell, measured using a cresent wrench didn't have the proper tool for that! Looking up different couplings was going to be my next move, which was just made a little easier, thank you!

 

[MikDee]

Re: Inboard outboard air cooled engine

I tell you what I would do, as an experiment, for the time being, I would get a short piece of heavy 5/8" ID rubber hose or clear hose from Home Depot (whichever is stronger), then a piece of 1" hose a bit longer, stick the smaller hose on the lower unit shaft, then the larger hose, on the motor shaft, and slide it over the lower hose so they're even top, & bottom, then put 2 stainless hose clamps on each end of the hoses, snugged up tight. This may make up for the difference in shaft sizes also.

Or, if need be, get a short piece of 1 1/4" PVC, or ABS pipe, and slice it straight down the middle (lengthwise) with an angle grinder (so it will now it will be a "split sleeve", and compress some when squeezed) next slide it over the hoses on the shaft, And then put the hose clamps on (to give it extra rigidity) this sleeve can also be something other then plastic, such as metal, but I can't think of what? at this time.

I got this idea from my Fast electric R/C model boats that I've sometimes used fuel tubing as a coupling between the motor, & propshaft.

By the way, here's a link to a real inboard motor shaft coupling, notice the split sleeve design for reference: "http://www.boatdesigns.com/prodinfo.asp?number=90%2D868"

 

[MikDee]

Re: Inboard outboard air cooled engine

Ok, I just thought of something else important, as I think about this project if you decide to try the rubber hose coupling idea I described. Rubber has good grip on metal, but it is even better with contact cement, or weatherstripping adhesive like they use on cars window rubbers, or on the bellows of the outdrive to make a good strong waterproof seal. I suggest once you get a trial fitting on the hose coupling,,, on final assembly, take it apart, and put contact cement on the shafts, then put the rubber hose coupling over it as extra insurance for grip, & waterproofing (You must let it dry for 24hrs at least) to cure completely. Don't fear using it, because laquer thinner, or acetone will disolve it, but you probably have to cut the coupling apart to get at it.

 

[maxum247]

Re: Inboard outboard air cooled engine

MikDee, that gives me something to think on! Looked at some of the couplings on the site you suggested, may just be an option! Will try the hose bit first if I don't like it then I can always move up a level! Thanks again for your help! maxum247

 

[maxum247]

Re: Inboard outboard air cooled engine

Think I've come to the conclusion that I'm probably going to have to raise the motor up above the stern about 2in. Not enough room inside the hull to make the shaft connections easily with the motor level with the top of the stern!
This will be a benifit when changing the spark plug and also will make designing the exhaust somewhat easier, and it will allow more room for the suicide shifter that I plan to use! I will need to drop the lower unit about an inch or so, so that I have access to oil drain plug that's in the engine! Glad the drain came to me now and not after cutting the drive shaft to length and sealing the lower unit up tight in the hull! I could see myself under there trying to guess where to drill a hole thru the hull to get access to the oil drain on the engine and putting in one of those little baitwell plugs to seal up the hole in the hull afterwards!

 

[Lone Duck]

Re: Inboard outboard air cooled engine

That oil plug under the engine is a pipe thread. Have you room to use a 90 elbow and a length of pipe with a cap and come out the side of your box?

 

[maxum247]

Re: Inboard outboard air cooled engine

Sometimes it is the simple things that are so difficult! Yes, there is room for a 90.

 

[MikDee]

Re: Inboard outboard air cooled engine

Just a note here, if you try my idea for a hose coupling, then you should be able to tell if you need any more gear reduction, or not, before you invest in more money for a "Lovejoy coupling", or one like it. At this point I don't know if the motor will reach full rpm, bog, or lug, with direct drive, even tho there should be approx. 2:0X1 reduction in the lower unit.

I have a coupla questions, does the motor have a keyed shaft on it? Also, are you going to cut the shaft on the lower unit to make it shorter? and what size motor is the lower unit off? finally what are you doing with the exhaust, are you gonna run it thru the lower unit spout? By the way, the lower you put the motor (reasonably), the better the center of gravity.

 

[maxum247]

Re: Inboard outboard air cooled engine

Engine is a 12h.p. Briggs with a 1in. shaft with a 1/4in. keyway. The lower unit shaft is about 9/16 in. I think, can't exactly tell. That will be cut to aproxamately 3in. as far as I can tell right now! Maybe more, maybe less! It's off a 1964 or 1966, 9.5h.p. Evinrude. Can't remember right now, got it written down somewhere! I think 66! I like the thru the spout idea but it looks like it will go over the stern unless there's some sort of flex pipe exhaust I could figure out! I agree the lower the engine in the boat the better!

 

[MikDee]

Re: Inboard outboard air cooled engine

Ok, just throwing out some more idea's here, because I'm fascinated with this project (like my fast electric R/C boats). On the hose coupling idea, I suggest you try it with the PVC, or ABS, pipe collar over the rubber hose (minus the key in the motor shaft) for rigidity, if the PVC, or ABS breaks, be prepared to row home,,,lol,,, But, if need be in the future, if you can get a short piece of 1 1/4" stainless tubing (not pipe) and do the same thing as I suggested, slit it down the middle, and clamp it over the hose (by the way, use as many hose clamps, as will fit) that won't break! I would also think this design whatever material you decide use, will have a tendency to keep everything inline (to run, or spin, true in a coencentric circle) in fact, I'd suggest to put it all together tight (without the glue) then mark out, & drill out your bolt holes, & mount your motor (temporarily) for best alignment. One final thought on this, in the future, you might need to add round rubber vibration dampers under the motor, I suggest you try it as is first though.

Next, I could be wrong, but I think you'll need to block off the exhaust spout on the drive, if you don't use it, (basically it is a hole in the bottom), and water will come into the boat, and seek it's own level inside, (matching wherever the outside waterline ends up being with weight in the boat). Besides, I like the put, put, of a lawnmower engine thru a long piece of ordinary threaded black pipe out the back of the boat (I believe that's the matching thread on the exhaust port of the motor) standard pipe thread.