Outboard to inboard mod?

[Piraten]

This might be odd, I couldn't find anything with search.  The old inboard was pulled years ago, but the shaft is still there, currently have a 9.9 Nissan hanging off the back.  Since I don't use the engine all that much, I am wondering if/how I can yank the lower unit off the outboard and have it drive the old shaft.  I realize the transmission is in the lower unit, will need remote controls, and a way to get the exhaust out.  Maybe a reversing prop so I don't need the reverse in the transmission.  Or, a transmission from another boat that has a blown engine.

The thought was to put a much lighter/modern engine "that's already paid for" in there.  Lighter and smaller to yank out for repairs, easy to get and store parts.

I was going to try electric, but eee gads, the cost of the systems, batteries, make it not so interesting.

As much as I understand atomics and small universals last 30+ years, I can't find one at a price I am willing to pay.  Also, this was just just more a tinkering train of thought.

[Godot]

I've never heard of anyone doing that. I wonder how well matched the prop will be for the motor (is there enough torque to drive it). And I wonder what real benefit there is.

However, if you are in the mood for an engineering challenge, go for it.

If you are going for the  challenge I'd still go electric, though. I bet you could put together a system for far, far less than the commercial electric setups. What's involved? An electric motor of adequate power, some pullies and a belt to transfer the energy to the prop shaft, some batteries to hold the juice, and a way to charge the whole setup. Of course, batteries get heavy.

[Piraten]

I looked at electric and even am on an electric boats mailing list.  When they get into the different controllers and doohickies, my brain melts.

The thought was to get the outboard off and put it inside.  I've seen the briggs and stratton engines used, just wondered if I could pull it off with my current outboard.  Understandably I need to change the vertical shaft to drive horizontally.  Current OB has electric start and a charging sytem, although tiny charging. 

As to benefits? Dunno, was just an idea kicking around in my noggin.

-Most marine inboards rot before the actual engine hours are used up, rebuilds expensive, new inboards expensive.
-Made modular so the 80lb engine can be pulled and brought home to beat with a hammer if things aren't working, as opposed to a 300lb atomic that takes four midget gorillas to get it out of there.
-It already has electric start with pull start backup.
-Water Intake with "y" valve so it can be easily flushed with fresh water.
-Torque is easy enough to convert with gear reduction.

[tomwatt]

I don't know how well it functions, but there were a couple of designs putting an outboard well underneath the bridge deck steps on some Crealock-designed boats. Seems like the outboard would be starved for air in there, and Lord knows how the engine would perform in that position. A different kettle of fish from what you are asking though.

[Captain Smollett]

-Torque is easy enough to convert with gear reduction.

One question is that by the time you reduce the torque enough, do you have any rpm's left to do any work?

Outboards have small props, and compared to the shaft in your hull, TINY shafts.  They also have smaller flywheels for a given horsepower.  ALL of these things matter.

I don't know how well it functions, but there were a couple of designs putting an outboard well

A MUCH better suggestion, in my opinion, than trying to mate an outboard to an inboard shaft + prop.

[Wade]

Anything can be done but I could never accomplish that task. What about an electric motor to the shaft powered by a stand alone generator, I've been thinking about this a little.

[Captain Smollett]

Anything can be done but I could never accomplish that task. What about an electric motor to the shaft powered by a stand alone generator, I've been thinking about this a little.

Search this site; it's been discussed many times.

There are reasons a lot of people looking into this give up on it before implementation.  It CAN work, but there a LOT of downsides.

One of the biggest problems with electric is simply the power involved.  If using the motor to do much more than just get in/out of a slip, that is, to attempt to use it how we are accustomed to using our mechanical engines ("fighting currents," long days motoring on the ditch, etc), the power is nearly prohibitive.  40 Amp or larger cables, HUGE battery banks, etc.

If you are going to carry a mechanical engine driven generator, why not just hook that engine up to the shaft?  Why the "middle man?"  (I know there are some good reasons to do it, but EVERYTHING is a trade-off).

I don't want to sound like a naysayer on electric...I feel I always do...but the engineering demands of replacing a true mechanical propulsion system are pretty steep. 

And, by the time you climb those steep demands and have a system that actually functions ALMOST as good as a regular engine, your boat is far from KISS.

[Piraten]

Thanks for the responses, I wasted some time on the big web and it came down to...
-Yes it can be done.
-Not worth the hassle
-Water would need to be on a seperate pump.
-Gets complicated.
-I'll never finish the project.


Guess I'll go down to Don's marine salvage and look for something to rebuild, or just close my eyes when I look at the transom.

[CapnK]

Wade - Kind of a "hybrid" drive - yep, I thought about that too, found basically what Smollett says. If it would work, in an ideal world :), then Piraten could use his powerhead as the "generator".

What if you glassed a tube into the keel, and used a PWC-style jet propulsion, with the O/B being short shaft, located in place of the old A4...?   ;)





OK, just kidding - because an outboard with the jet foot loses like 15-20% of horsepower as compared to the same powerhead with a regular prop. But that makes me think - an old-school PWC like the original Wave Runners had IIRC about 55hp, in a smaller package than an A4. Why not put one of those...

Ahh, never mind. Back to the Merc 6 in the well... ;D

[Piraten]

Lol, I also have one of those pocket bikes in the garage.  I can pick the whole thing up, so the engine is only half that weight. But then I would need air cooling and it is two stroke. No reverse.  And...would sound like a angry hamster in there.

Not through the first cup of coffee yet.

[CharlieJ]

There USED to be an engine-drive setup on the market that did just that- outboard power head, and jet drive below, It fit through the hull, with the power head mounted down below, directly on top of the drive- Called a "seawolf"or something like that (Memory fails) In the 70's a buddy investigated one for use in a trimaran he was building.

Also, Evinrude used to make a SailDrive, that was an outboard  power head , coupled to a lower unit, but without the leg. Required a pretty large hole in the hull for the two halves to couple together through. 15 HP 2 stroke engine if I recall correctly.

I don't believe either unit is still on the market.

[SalientAngle]

I believe this may be the critter Charlie refers to:
http://impliedconsent.us/impliedconsent/Zephyr_Saildrive.html

[matt195583]

After spending around 12 hours in a muscle cramping head spin inducing position removing the prop shaft coupling to my 20hp yanmar. If I had a major engine failure I would very seriously look into fitting an outboard in a well.

$2500 for a new 15hp OB V $12500 for a new inboard diesel and the ability to lift it out and work on it in the comfort of my brothers workshop sounds pretty darn good to me. Plus massive weight savings 15hp OB about 40 kg 20hp IB about 220 kg.

[CharlieJ]

and I doubt you NEED a 15 HP.

Tehani drives at hull speed with an 8 HP, running UNDER the start setting, probably using 3-4 HP. I HAVE moved her with a 2.2, but stopping was a

B i**ch!

Necessity, my 21 footer, does 5-6 with the 4 HP, running at a high idle.

Amazing how little engine you REALLY need.

[CapnK]

CJ - how well did Tehani move with the 2.2? Every dang time I lift up/move around my 6hp in the laz, I look longingly at the sub-30lb 2.5 Suzuki on the back of the dinghy and think "Hmmm, that's *way* better than an oar..." :)

[CharlieJ]

Took a good while to get her going, and as I said, stopping was a BI**h, but it moved her ok. I was moving around in the marina, after a hurricane threat, and had the 8 HP removed. I wouldn't want to try cruising with only a 2,  ICW anyway, but a 4 would work well. Doubt we used that much HP at any time.

Oh- and my new 4 hp Yamaha weighs exactly 6 pounds more than the old 6 HP Johnson.

[matt195583]

Absolutely Charlie the 20 hp that is fitted is well over powered, before the trip north last year I had the prop pitched correctly and in smooth water can cruise at 5 knots a touch above idle......... Also on that same trip a friend in a 36ft spray with a displacement of around 13 ton had a water pump failure and lashed his dinghy to the side and motored about 20 mile all with his trusty 2.2 tohatsu  ;) 

[boblamb]

It looks like I 'm going to change  my inboard to an outboard.  The little 1gm10 has given up the ghost and there is no way I can afford to have it rebuilt.  I have 'read all the threads here and have a question.  What options do I have about selling the 1gm10 as is?  Who could I contact about buying it?

What to do, what to do???

Bob

[okawbow]

On a trip down the Tenn-Tom a few years ago; I repaired my 1 cyl. Yanmar at a marina. The cost was less than $150.00 in parts and took a few hours.

Get a good repair manual for the motor and follow it to the letter. It doesn't take a rocket scientist.

[boblamb]

Thanks for the reply...my cylinder head is shot...leaked saltwater into the engine possibly piston and crankshaft damage.  Head alone is$550.  Probably have to pull engine out to asses the total damage.

At this point I'd Rather just hang an outboard on it