mcgyverk

Ok guys, my first post here. Been reading for a couple of years now, for ideas and inspiration. My question is about wet exhaust systems. Do I need to install some sort of check valve or one-way valve in my exhaust to prevent the water from backing into the engines when I kill her or she dies?

I am building my racing boat from scratch and just need some info. Thanks. I will post some pics and plans as soon as I can get a chance.

blizard05

(NO)

STEVE MARSHALL

blizardo5, Thats a bit blunt mate (NO) What kind of answer is that????
mcgyverk, welcom to RCU Gas boats, sorry I can't answer your question but I hope someone will answer it better than the first guy.

Steve

PEERPSI

Don't own a wet pipe myself but I understand the pickup is on the hull so no movement no water going in. If you have movement your engine is running producing exhaust and taking the water out with it to cool itself. I believe it also effects the engine tuning.

No check valve needed.

mcgyverk

Hey guys, WOW fast answers! Ok on the check valve. STEVE: I have not completely made up my mind yet, but this may be a squirt drive setup (jet drive). I guess I need to give you guys more info. This is a Sabre Canard hybrid ( [link=http://www.rcuniverse.com/product_guide/boatprofile.cfm?boat_id=204]This Boat[/link] ) that has a total hull length of 72" ( Yes thats 6 feet. LOL). She has twin inline 33cc gas engines. And since I work in a machine shop with nice equipment I have been toying around with Supercharging them just for kicks.

blizard05

May be blunt, but the answer is still NO. I have several WWH wet exaust set ups.NO water back up to motor

blizard05

Not the best choise of hull for a jet drive,Also stick with a (dry pipe)for more power

Jamming

Also if you are building a racing boat, You might want to consider a dry tuned exhaust. Wet pipes do rob some power and slow you down. Most boats that run a wet pipe are sport boats or better known as play boats. The pipes are designed to be wet due to the fact that most are running a clutch so the pipe doesn't overheat when running. They also run much cooler for enclosed applications. If you are building a race boat you will find a dry tuned pipe much faster and increased rpms. A can muffler is the slowest and wet pipe next and a dry pipe last for the most power. Depending on engine and pipe you can adjust the dry pipe for length "hence" tuned pipe. A wet pipe uses only a coupler and a pipe, So limited tuning because of the water in the pipe breaks up the sound waves and causes differnt back pressure depending on RPM's so tuning a wet pipe would be very difficult problem. But if you do use a wet pipe you won't need and check valve as people say. "no" You can run a dry pipe enclosed you just need to consider the heat and adjust the venting to compensate for the extra heat. I have two warehouse hobbies team pro boats and they are both fun and have wet pipes, but they would never be competitive at 45+ mph. same boat with a dry powermaster tuned pipe i got 55+ and found the limit of the hull.

pyro1

I have 2 boats with wet exhaust and if you pick up the boat from the water,remember bow up in case there is water in the pipe it will run out. If you are in an akward position like in a row boat and pick up the boat stern first you WILL have water run back in the engine. I know I have done it.
Glad to have you on board.

Pyro 1

TwinJetMax

Also bearing in mind that a valve in a tuned pipe will stop the gases getting back into the engine.

Being a jet drive guy I don't think that that hull would be any issue for a jet drive. It is essentially a tunnel hull with a bit of a hydro aspect to it. Many of the river race jet boats look similar to that. I am currently building a tunnel hull river race jet boat myself.

http://www.rcuniverse.com/forum/m_65...age_146/tm.htm

Mine is the boat at the top. It is a bit different to your but I wouldn't think that it would have any problems.

What sort of jet are you looking to put in it. It will need to be big.

MrMikeG

That hull is a reverse rigger basically so where would you put the jet intake?
If your "supercharging" a 2 stroke you don't need any tuned pipe as well, since the case will be pressurized from the supercharger it would not let the returned charge come back from the pipe.
I think you will have a hard time finding anyone to race with.

TwinJetMax

In the normal spot. The central hull.

mcgyverk

Ok, I think I have decided to go with a prop drive. I have to do some calculations on total weight, hull draft, on-plane height, and other stuff so I can order the correct prop. I would love to install a scale outdrive like the MHZ drives. Especially if anybody has one laying around for CHEAP ( or free). HA!!!!! LOL Yeah, right.

Justaddwata

My Feedback: (3)

You might want to express aloud a few more of the options you have in mind for this build as it is sounding like you may have plans to learn a few lessons the hard way.

Canards can be very quick when built and trimmed right. Trimmed wrong they can disappoint.

What motors are you using @33cc's a piece? She is sounding like a heavy Canard.

Save your time and $$ and go with a plain old strut and rudder. The stern drives wont take that kind of power for very long. An inline stock zenoah will have you grinding teeth in short order. Not convinced you will find too many going cheap (or free) but admire your confidence there

Trying to mechanically supercharge the motor is something that several have tried and thus far I dont believe any have achieved actual gains. The successful option that is a standard in the hobby is tuned pipes which make some very notable power gains. Blowers will always take power to make power - you will need a very efficient blower to give yourself any chance to make up for the losses. Dont get me wrong - I hope you succeed with the idea - The world will be your oyster if you do.

MrMikeG

The "central hull" doesn't touch the water on the rear of a Canard, so how are you going to pick up water?

TwinJetMax

Oh my bad.
Should have found that out.
It probably wouldn't work then.

mcgyverk

Just updating. Almost done with the cylinder water jackets. Been reading up on 2stroke turbo/superchargers.