Help with stern tube/propshaft design

Hi, I've been getting lots of useful info from this site for a while, but now I am stuck.
E-bays fault again, rush of blood and I end up with an 18ft fiberglass boat. Hours of searching the internet and all I can find out about it is that it was one of about 5 commissioned by Honda in the early nineties. Powered by the little GX-160 Honda air cooled engine 163cc 5.5HP.
It was a bare hull except for a propshaft and prop lying inside the boat.
I have found a photo of the engine bay and the engine was fitted with a 2:1 reduction gearbox with wet clutch, this has a 20mm keyed output shaft so only ever operates in forward, reversing (and steering) is achieved with a fancy sort of bucket system behind the prop. This is all taken care of and fitted/working.

My problem is how to connect the reduction gearbox output shaft to the propshaft. My blurry photo of the original engine bay definately shows them connected by some sort of flexible coupling - but after test fitting my engine, the fresh air vents for the engines air cooling fan is in a different place to my blurry photo - which leads me to guess that either this boat was not fitted with the reduction gearbox and just had a centrifugal clutch fitted to the engine output shaft, OR, that it was driven with the reduction gearbox but used a chain or a belt to drive the prop shaft.
After much reading I think I am right in assuming that the design of the stern tube will decide how I am going to drive the prop shaft due to how the thrust is applied the hull?

The image below is a drawing of what I have, another problem is that there is an unknown bearing, the shaft is 20mm and the stern tube is 40mm, the only bearings made in that size are thrust bearings but there is nothing to hold it in place (all I got was a ball bearing the ball bearing race and a couple of plastic bearing seals)



Just realised I missed a circlip off the drawing, it fits in the recess on the stern tube and goes between the lip seal and the bearing on the shaft.

Any help on how to connect the prop shaft to the engine and on the missing bearing please. The boat with this engine in is only going to do 5 or 6 knots and with the reduction gearbox about 1800 revs max.

 

Thought I would add the only info/photos I have of the original boat. On the photo of the engine bay the grey "tube" is offset to the left of the bulkhead, on my boat it is central, which leads me to think that on my boat there was no 2:1 gearbox or that it was belt/chain driven. The "tube provides cool fresh air directly to the engines cooling fan.

 

Honda Explorer

Hi, not sure if I maybe can help. I have purchased one of the same boats only this week. My boat is complete I believe, engine is out at the moment but I think I have the parts to refit. Certainly the complete prop assembly is in position.

 

Additional pic

My Explorer

 

Oh wow how exciting, I guess as you have noticed no info anywhere. I have just sent the shaft away to be modified, was just going to guess how it worked, must stop them doing anything to it - if they havent started.
Yes please, all info and photos very much appreciated. Is the big hole in the bulkhead for ventilation in the center on your boat or is it offset.
If you let me know your email ad I will mail you the magazine review I have of the boat.
Brilliant

 

pics

Yes, I saw this as an interesting project, thinking how unusual. . as you say very little around .. in fact yours was the only info I have found so far. The air vent is off set to port looking from the rear of the boat. I started the engine last night. I've only had the boat 2 days. It just needs some TLC. The top of the boat has oxidised the pic I have posted is just after I washed it off a bit. It should restore back to gloss red if I use the right approach, not sure what is best to use at the moment. Yes I will send my email address. Good to find someone with a some knowledge, hopefully I can help fill the gaps.

 

I have loads of questions, strange thing is the hole is central on mine, did not realise this until I had paid a fortune for the 2:1 reduction gearbox, I am dying to know what couples the gearbox to the shaft. Will you be removing the propshaft, on mine it looks like the bearings had corroded due to the engine bay filling with water and that water getting into the stern tube.

 

pic

I have to go out today however, posted some pics that might help.