gonggongboy

Hi im planning on making a 7ft cat. I found a guy on ebay that sell pocketbike for little to nothing so i was going to use two of them with a 70cc upgrade kit x2. Im gunna make as much of the hardware my self and im building the hull. Im just wondering if i dresesed up the motors and lightened them that they would move the boat really fast.

gonggongboy

I just found a big-bore kit that can make a pocketbike motor 100cc. Also im planning on using two motors not one. Or should i have one with a gearbox. I want two drive lines.

Justaddwata

My Feedback: (3)

I guess I am not sure just what your direction is with this project.

Catamarans are very tight on interior space to accomodate power plants. Mounting a power plant on the tunnel can work though can also make the boat top heavy. Mounting the motors in the sponsons will lower the center of gravity and make the boat more stable in corners but not many motors are narrow enough to fit in most large cat sponsons.

Not knowing what motor your considering it is also hard to tell where you plan on fitting them.

Are you building the hull yourself?
What motors are these and any idea on their weight.
I have a bunch of pocket bike motors - all much smaller capacity (39-50cc), water cooled, high reving and good HP. I would recommend looking for a water cooled motor - for both performance and cooling considerations. Bike motors also tend to be pretty heavy - even the 39cc is probably 3 or 4 times the weight of a zenoah.

I have a couple of 6ft cats with a single motor mounted on the tunnel and it does impact the cornering. I have a bigger cat though the motors are in the sponsons.

I would focus a little less on motor displacement and more on weight and fit - adding more power to a heavy boat wont necessarly make it much faster.
Let us know more about the motors and hull your considering and I am sure we can get you some better advice.

Heres a few of my cats
http://justaddwata1.multiply.com/pho...y_Motor_MH_Cat
http://justaddwata1.multiply.com/pho...Cat_Dewalt_Cat
http://imageevent.com/justaddwata/myboats/geicocat

Also a bunch of other peoples pics that may give you some more ideas
http://imageevent.com/justaddwata/mo...herpeoplespics

gonggongboy

Im gunna lay them on there sides tight against the hull and then im gunna grind the cooling fins and make my own waterjacket.

Also im building the hull myself. But yea ill be working with the motors a bunch to lighten them and ill remove the pull start for something else.

gonggongboy

http://cgi.ebay.com/ebaymotors/Pocke...Q5fAccessories


http://cgi.ebay.com/ebaymotors/Mini-...ltDomainQ5f100

gonggongboy

Also the hull im gunna build from brain or if i can find plans blow them up

Justaddwata

My Feedback: (3)

Just a suggestion but I would stick with a motor that is already water cooled personally - you might spend a little more upfront but I can see you spending a lot of time modifying a $60 aircooled motor only to have something go wrong and your back to square 1. IF you look at the transfer ports on the air cooled motor vs the water you will see there are 5 on the water cooled (the large one over the exhaust is a water gallery - not a transfer port) http://cgi.ebay.com/2-STROKE-MT-A4-3...3286.m20.l1116 and I would bet it makes more power stock than a modified air cooled motor.

If your set on the aircooled motors and building on a budget then I would leave them aircooled and just make sure the design has good airflow past the motors.

A single motor setup with a gearbox may be easier in someways though the expense of having a good gearbox to handle the power is in the order of $400 unless you build your own.

gonggongboy

I know a guy that builds custom race cars and other custom stuff and im good friends with so im thinking of having him make me custom parts and waterjacket.

Also the waterjackets you showed me are a little to much than i want to pay im trying to build this boat under $500.

I dont care if its race qaulity since im just gunna cruise around with at a local lake.

Also do you know of eny plans for cats ill just blow it to size.

HendricX

Do a search on this board for member MaxCorvette , and/or MaxCat .

Anywhere you would find the drawing for a MaxCat-V1 you've just to scale up .

It's a proven concept ... there are already scaled-down and scaled-up builds.

viperhulls

Honestly do not waist your time and money on the engines you have chosen, compared with a 39cc water cooled genuine or replica Blata engine there is no contest. I don't know how much you can pick them up for in the States probably around a few hundred each which will be worth it instead of sinking your money into a project that is going to cost you more than it is worth. not trying to be a kill joy but don't get caught up in engine capacity over quality. I will bet my left nut that the blata engines will run better than the engine you have chosen even if you modify it. I have to agree with Jaw on this one, he knows his engines. Good luck with your project.

sikR31

dude i was looking at a 70cc pit bike motor for my 65" deep v. now i am going with a 50ccw/c polini replica. a lot easier thanfarting around with air cooled.i can get it for $350 AU not too bad considering genuine are at least 3 times that.
my build has cost me $150ishin materialsso far. nearly finished my mould...now i have to convince my missus to let me buy my motor

jacob711

blata replica engines are pretty cheap too, i can get new ones for $180au well last time i checked i could

sikR31

thats pretty good. i did some research on them on the pocketbike forums a nd found that the polinis are a bit more reliable and powerful. I LIKE POWER...
those engines have got a bit of guts... they push a bike+rider up to 90 kph i wonder what they would do in a boat....

gonggongboy

Ive been looking around on ebay for watercooled pocket bike motor kinda hard to find for cheap.so i may stick to air for a little bit and build waterjackets ive got what im gunna do planned out real well.

Im still trying to find a hull help me out. i need one were i can cut the pics out and use as stencils.

sikR31

www.zuma.com.au pocketbike dealer in aus. chuck them an email see what they say
about the hull, pm dwr9 and ask him about his plans... i forget where i got mine from.
i think i had them on disk around here somewhere from when i went to the print shop

viperhulls

I haven't had much to do with the polini's but what I here the bizetta top end on a blata bottom end can't be beat, I know Matt had a polini in one of his boats maybe he can shed some light on them how they compare to a blata. I am very happy with my 50cc genuine Blata which iv'e clocked with a gps on several runs now at 96km/hr or just under 60m/hr.

jacob711

the only way i could see the air cooled engines going into a boat is if they are mounted on their sides with the cylinder heads going into the sponsoons so their is enough room to fit exhaust headers under the cylinders

your also going to need counter rotating engines, which means you have to turn one engine around and run the drive off the pull start end which means you need belt start and you also wont have any clutch which will make it hard to launch the boat unless you might be able to fit the clutch to the other end of engine

you will also need a walbro carb and manifold for each engine, reason being is stock carbs are gravity fed and wont work in a boat and they are also non adjustable and crap, the walbro carbs however pump fuel themself and are easily tuned by the turn of a screw and give better performance

it will be an interesting and challenging project for sure, but it would be cool to see done properly for sure

however don't expect it to be very fast, the air cooled engines even after being fully ported and modified still make less power than a stock blata replica enigne (water cooled)

do what hendricx said and get the maxcat plans and enlarge them



ey viper i actually just picked up bizetta replica 50cc engine, apparently the fastest out of the replica engines, only cost me $160 too bad its going into a bike not a boat

sikR31

hey jacob where u pick that up from?

jacob711

www.pocket-bike-racing.com.au someone was selling it used but just rebuilt and with a new dellorto replica 19mm carb, only problem with the bizetta engines is that they have an inbuilt water pump which is at the bottom of the crankcase when the engine is mounted in a boat which makes the engine 2"-3" taller (top heavy) you could probably cut the water pump part of the cases off though

gonggongboy

http://www.youtube.com/watch?v=Ebl0OLekygw

viperhulls

Check this one out, this is my 50cc Blata that nooh took some footage of at Carbrook on a practice day. Play it through to 2:25minutes and you will see real horse power, this is my Viper Stealth clocked at 94Km/hr and I now have it doing 98km/hr. http://www.youtube.com/watch?v=hiom4TI5smI

nooh

Remember it well Tony, Big Boat you brought with you that day, And the Power it had [sm=spinnyeyes.gif] Could have water skied behind it I reckon.


Henry..