.12/.15 engine

[bangka]

hi! i'm going to build my first boat.. about 32" long.. i'm thinking of putting a .12 or .15 engine into it.. it will be either the os .12 cv-rx or the os .15 cv-rx.. does anyone have any inputs regarding these engines? also, is it ok if its not watercooled? even if its close cowled? thanks!! it will be a sport boat only..
also i will be using the mini-jet drive from graupner.. i already have 2 of these...

[Ron Olson]

Air-cooled engines need air! Otherwise they heat up the inside of your hull and drastically change the carb settings as the heat builds up. You'll be chasing the setting trying to get it right. Even with a watercooled head you can have the same problem.

[Hydro Junkie]

Listen to Ron!!!
In a boat, UNLESS its motor is totally out in the open, air cooling IS NOT the way to go. Even with water cooling, an enclosed engine needs to have vents of some sort cut into the cowl to keep from starving the carb of air. Since you are using the jet drive, this means no rudder. Most of the people I run with use rudders with a machined in water pick up. In the case of your boat, you will need a bottom mounted water pick up. Right off hand, I can't remember who makes one, though I have seen them on the market. It will require two lines to the motor's cooling jacket(or clamp) to keep the motor cool, one from the pick up and one to dump the water over the side. In my scale hydros, I have to run a cooling tube almost two feet through the hull just to get to the motor, and then another six to eight inches to get the water back out . Your boat will be much simpler,so don't be scared of water cooling-water is your motor's friend :)

[bangka]

hi! thanks guys!! well actually i'm thinking of wrapping it with aluminum or brass coil like in the electric motor.. and the water pikup, i think i have an idea where to put it. planning even 2, one for motor and 1 for muffler.
another thing, what is a good muffler, i like it to be quieter, even if speed is sacrificed a bit.. is an airplane muffler better compared to car tuned pipe, with respect to lower noise level.
thanks!

[bangka]

and what do you think about k&b .18 marine engine? is it as good as the os's?

[BoatDoc]

funny you should ask about that K&B motor. one of the other guys was just telling me about it and said it was a "slug". i'm going to take his word for it. as far as a quieter muffler, i've been testing a wet exhaust on one of my nitro boats and found it to be quite effective at dropping the sound. i don't know know if it's set up the "right" way, but i've had no negative results from it. but i would stay away from airplane mufflers as they don't allow the high rpm running that a well made tuned pipe has to offer.

[BoatDoc]

by the way...i forgot to mention, you can make your own water pickups instead of buying them. i use brass tubing that i cut to length and sharpen, and i mount it to the transom using a landing gear strap for a model airplane. it works well, and costs about 2 bucks to make.

[bangka]

thanks boatdoc! yup thats what im thinking. i think its easy to make. if i buy a tuned muffler, how will i make a wet exhaust? because as you've said, stay away from airplane muffler.. are tuned pipes under 30$ good?

[BoatDoc]

if you use a .15 engine you can get a mac's tuned pipe for something like 25 bucks from BBY racing. if you go smaller than .15 you'll have to look at the car pipes and i don't know much about them. what kind of speed are you trying to get out of your boat? the reason i ask, is because i use a .21 on my 31 inch mono! as far as the wet exhaust, i'm just trying it out right now. but here's what i did. i drilled a hole about 1/2 of an inch before the peak of the tuned pipe. i used a tap and drill for 6-32 thread. then i put in a 6-32 pressure fitting with some thread lock on it. i ran my water line from the transom to the head and then to the fitting on the pipe. i don't know if this is the right way to do it or not, but i'm satisfied with the results and it sounds really cool and helps to drop the temp inside the last half of the pipe.

[bangka]

it would be just a sport boat, not too much speed.. this will be my first boat, so i guess i just have to get the feel of driving a boat first.. i am from the philippines so i guess i just have to order everything from one source.. maybe from towerhobbies, because the shipping is kind of expensive, if i order from diff. stores.

[Hydro Junkie]

Just out of curiosity, where in the Philippines? I've been to the Islands several times, so I wonder if I was close by? As for mail order, you might also look at Sig Manufacturing(sigmfg.com). They have a wide assortment of plywoods and spruce to choose from. I know they have other materials as well, I just didn't take the time to really get into the catalog. They may even be less expensive than Tower :) This would be an option if you are scratchbuilding from plans. You haven't said what kind of boat you are doing, so I'm just trying to give alternatives :D

[bangka]

hi junkie! right now in metro manila, working here. but sometimes i do went home to hte province, but only sea water there, no lakes. here in manila i'll try in rivers.. at first i was thinking of a classic runabout. but right now i'm starting a plan for a sleek type boat.. something like a VSV type hull. powering it either by jet drive or prop.
my problem regarding the materials is the drive hardwares, hard to find it here.. no problem with balsa nd ply.

baruto

[Hydro Junkie]

I was in Manila December of 1985, with stays in Olongapo City and surrounding area in 1984 and 1985. Most of my time was in the Subic Bay area, as I was in the Navy at the time. Now that I know what your'e working with, let me make a suggestion. As you may end up in Manila Bay, try to get parts made of stainless steel. They don't corrode as easy. I read earlier you wanted to use a jet drive. Is this still the plan? For use in rivers, this would be a safer way to go. Come to think of it, I never saw a lake or pond anywhere between Subic Bay, Manila and Clark Air Force Base.

[bangka]

yup, jet drives.. yes you're right, i think its safer to use jet drives. in this way the impeller is protected from from accidents..
thanks for the advice!