Jet Boat conversion... Ideas??

[Guyph_01]

Only problem with a 50hp as seadoulou suggested is the weight as i only be able to afford the older engine that weight quite a bit.... I was thinking 30-45 if i can find something smallish. Hummm, I'm serious until i find a wall like lake of funds or something. We use to have a 15ft boston whaler square nose type fiberglass boat back in Mauritius and it was powered by a 25hp Mariner. Had plenty of go to pull us on ski's, a knee board and a wake board. And i lifted this explorer and it doesn't fell that much heavier.

Crisso, What do you have in mind for the rear alu transom? Could you explain or draw something up? Yes i'll get the jet intake area. Thx for the tip

Seadoulou, inboards are 3times the price of an outboard unfortunately

Yes it would be easier to find a small working boat but at the moment i'm at the stage where i want to build my own stuff and like it better than buying something already working. Maybe when i get older and wiser i'll just buy something thats already working or new

Did the last round of patches 2day and will let it set for 36hrs. Time will tell if i fixed them all.

Thx for the input guys has given me ideas and much appreciated thoughts


Ohhhh and check this out if you ever want to go on holidays
www.dodolidays.com

 

[crisso]

What I had in mind would be virtually a box.Slightly tapered.The biggest end would bolt to the boat.Smaller end would have the outboard mounted to it..This would be able to be fitted without any chopping up of the boat.Being a sealed unit,it also provides extra bouyancy.Go to a boat yard and wander around.You will see many alloy boats with a similar setup.Installed in the top would be a waterproof access lid and some bungs at the bottom of it.Any alloy fabricator could make it.Were it bolts to the boat would be at least 600mm and the outboard end about 400mm.

 

[Guyph_01]

Is that what you were thinking of?? Won't that cost quite a bit to fabricate?

 

[Guyph_01]

Well 2day i pumped up the tube and i'm happy to say i've stopped 97% of the leaks. Found two small ones and forgot to patch one up. So quite happy with this and seems like the next step is to figure out the transom build

 

[Guyph_01]

Ok stopped all the leaks

Now i though of doing the transom out of a 3 or 4mm thick stainless steel plate bent to shape similar to the drawing below and welding two triangle on the sides and bolted to the back fiberglass...

 

[crisso]

Do it in alloy.Get all the holes drilled and get it powdercoated.Lighter,cheaper.The plate for the motor mount needs to be at least 20mm thick.Turn those triangles into rectangles and put a plate between the two of them where it fits onto the boat.BUT 100mm wider than the engine end.This will stop any sideways movement,and make it very strong.I have done this many times.Good to see you got away from the wood and f/glass

 

[Guyph_01]

hummmm, didn't think of Alloy, you mean Aluminum right? Isn't Aluminum very expensive? Could you draw something up? i'm not to sure of what you mean.
Thx

 

[Guyph_01]

Is this what you mean?

How thick should A,B,C and D be?
Thx

 

[Guyph_01]

After some more brain storming it looks like getting a think plate or plates welded together to make the required thickness for the above A plate for the transom will be quite expensive and will add weight. So i thought of building it using bars. What do you think?

 

[Guyph_01]

Also, I want to try and keep the fuel and speed senders and gages. Is there a way of hooking it up so i can work without the control box?
I'm no expert with the electrical side of things and get a bit confused when i look at the wiring diagram.
Thx

 

[LouDoo]

Theoretically both should work, but there's a big difference between theory and practice. I don't have a wiring diagram for your explorer, but looking at a diagram for one of my ski's it looks like all you need for the fuel gauge is 12v. and ground for both the sender and the gauge and a signal wire. The speedo you will need 12v. and ground at the gauge, and just a signal wire from the sender.

The speedometer runs from a small paddle wheel attached to the ride plate, I don't know exactly how you are intending to close off the pump area you may need to relocate the speedometer sending unit, the other problem that I see when you add the new transom it's probably going to cause increased turbulence and cause the speedometer to loose more accuracy than it already has. You might be better off to mount a pito tube type speedometer to the new transom.

Lou

 

[Sink]

This is just a thought but how about building it out of plywood and covering it with fiberglass then reinforcing it with aluminum where the engine (motor) will attach??? Kinda like they build most boats. It just seems this would be strong, light weight and not as expensive as building it out of all metal. This may have been discussed before so if it has... NEVER MIND!

 

[LouDoo]

Sink,

It has been discussed before and I personally think it's a good idea because it would add buoyancy where it's need at the motor. I'm not sure why the idea was dismissed.

Lou

 

[Guyph_01]

This was also my original idea, i'm still not sure what direction to take.

So far the materials cost for the aluminum is going to be cheap as i have a scrap metal yard close by that i ask will charge about $50 for all the aluminium i need. Then the welding will need to be done by some one and this i think will cost as estimate $100-300. Plus powder coating would cost about $100 plus the odd stainless screws.

For the Plywood option, its only the cost of the materials that will be there as i'll cut and do it myself, Total marine plywood needed is about $100, not sure yet on fiberglass, resin and hardener. Can i use any type of plywood or should i stick only to marine plywood?

Cool well hopefully i'll be able to get both the fuel and speedo to work. If i can i'll compare it to a gps and then see if i need to go with the pitot type.

I have been removing all of the parts on the boat that isn't needed, stripping it. I'm stuck with the reverse and steering cable that are bolted to the back of the boat. I know i've got to undo that 19mm nut from the inside but the cable turns on itself. even when trying to hold it with vice grips or a 10mm spanner and with loads of crc, it just doesn't want to undo... Is there any trick to get it out?

Also started to block the holes, i.e the exhaust, water pickup outlets, main shaft hole. Still not sure what to do about the pump area. I'm thinking i'll just try it as it is and see what happens with the outboard.

 

[Sink]

Maybe try heat to the nut. If it's corrosion, that should break it loose. If not, just cut it!

As for the marine grade plywood, I wouldn't think it's necessary but how about some more input? Since the fiberglass will completely cover the wood, it wouldn't really matter if the plywood went away after the fiberglass was added.

 

[LouDoo]

Just my opinion, like rectums everybody's got one. I would use marine grade plywood, if the plywood rots you'll lose all structural integrity, or course if the fiberglass job is done correctly you shouldn't have water intrusion, but for a few dollars more I would go with the marine plywood or at least treated plywood.

Just one more thought, I really don't want to muddy the waters, but for the price you can get aluminum, sounds pretty cheap you might want to reconsider using the aluminum, it's going to be a lot lighter.

Lou

 

[Guyph_01]

Don't worry about the muddy water, nothing has been bought yet and yeah Alu materials will be cheap but welding might be expensive if i can't find a "Friend" to weld it up for me. Weight will definitely be less with Alu.

Thx for the input.

 

[Guyph_01]

Good news, Have pumped the tube 24hrs ago and its still holding plenty of air. It did go a little softer and i did find three very very small leaks. Quite happy and confidant now that it will be good enough for a day out on the river.
Doesn't look pretty with all the patches lol... and still needs another clean

 

[crisso]

Guyph.If you can get the aluminium,do it out of that.Ring around to get a welder.Ring a powder coater.They know all the best mig and tig welders.I set up and ran Australian Powder Coating on the Gold coast for many years.So I am not talking out of my arse.The P/C should only be about 60-80 dollars.It's only a box.
The design is pretty good but put a top on it.Then an access hole like a spinout so you can do the bolts up.The bigger you make it,the more float you will get out of it.On any other boat,they are called in Aussie,a pod.Every 2nd boat has one.The motor sits further out the back,runs in cleaner water and in hard turns you get a lot less cavitation.
Look at it another way.Would you buy a bodgy plywood/glass layup over a well made aluminium pod?Probably no.Do it once and do it right.God man.I have run and set up that many boats.Do it in Aluminium.You will find a bloke that would weld this up for a couple of cartons

 

[Guyph_01]

Would you be able to draw something up for me? Also should i also add another plate on the bottom of the boat so that it bolts both side of that flat extension and vertical face also covering the pump hole? I'm scared that with the force of the engine it will rip and cause the engine to fall off...

Add something like this, with the triangles on the side for added strength..

Bought some alu tubes and plates at the scrap yard net to me. Got everything i need to do that last design i drew up and it cost me $30.

As you said, now i'm ringing around to find a welder

 

[crisso]

Guy ph.I am absolutly crap on the net.I can type,I can answer,I can shitstir ,I can not stir,.Please read what I previously said.I am flat out posting a letter letalone a drawing.Mate! I would if I could.it took me 1year to get a photo on here.Ask the others.I can tell you how the ins and outs of a ducks bum works.I can tell you how to build a triple compounding turbo diesol motor..You post a drawing and I will say yes or no.please

 

[Guyph_01]

Ok well this is what i'm thinking. The blue is the boat sandwiched between the two aluminum custom parts.

(The top plate will have two sides. Only one side is shown in the drawing)

What do you think?

 

[crisso]

You have now got the idea.Make the bottom plates as thick as you can.That is great!!!,,,3-4mm
Top plates.Where it bolts to the boat is where it has to be the biggest.Its called torsional twist.The bigger plate on the boat,the better.Beef up the connecting side plate.You are now on track for this:thumbsup:

 

[Guyph_01]

Should i do all the plates in 4mm? Or do i need thicker? Also would this suit 25-40hp or is 40 pushing it?
Is this design good or does it need more? Lol the drawings has well evolved from the first one
Thx

 

[crisso]

4mm is very good.If you can get a sheet of that or a good sized piece,all is good.Tell me what you can get and we will go from there.God man! don't you sleep.Only kidding.Tell me other sizes you can get for cheap.