can anyone please tell me what are the MAIN CAUSES of zenoah gas engines in boats cutting out ,i have a fairly new (less than 4 litre ) omen modded zen in my mono and without fail everytime i take it out it will run good 10 mins then just out of the blue cut out ,now cause engine is new i wouldent suspect electrical problem ,i have good fuel and filters ,put carby back to stock setting ,do kits on carby often ,always get new fuel ,plugs always good ,now when it knocks out ill start again runs perfect about 10 mins then just cuts out (somedays better than others some days worse ) ,,i have an open hull ,no hatch cover could splashing water be shorting out plug to earth ,,any help as this is really P.....ing me off ,,,i thought gas was supposed to be easier than nitro ,but my nitros run perfect all the time

Nitros are reliable, I like that. They only stop if ingesting water or a bad tank interrupts fuel supply. Pretty much the same with gas, your problem sounds like you have tank issues.

I agree... I would be looking at the tank. First thing to check is that you have a good vent if using a hard tank. Second is fuel pickup location. Sounds like a bad vent to me though.

If you are using a HARD TANK remove it and inspect the line to the clunk as well as the vent tube as others have mentioned. Some people use a hard tank with the stopper to the rear and a solid pick up to the left rear corner , this works very well until you turn left or quickly slow down with a low fuel level . I use a hard tank set up as you would in a model airplane with the stopper to the front..There are many ways to keep water out of your vent line , do a search here and on Jim's site. I'll give a plug for my favorite systen,a IV bag on the vent tube. Good Luck Ed

Need to figure out if FUEL or Ignition ....

Fuel type missing is a soft power loss that sound odd, but not a sudden herky jerky sound that an ignition issue has.

Most common ignition problem is a BAD GROUNDING of Grey Coil to cases.

i will check my tank ,i have hard fuel tank with clunk just loose on about 3 inches of fuel tube (IS THIS NORMAL SETUP )and my vent is siliconed to top of hull so its easy to get air but minumul chance of water going in ,,,,,, ??also ed what do you mean by you favorite system being a bag on the vent vent tube ??

or experienced boaters just tell me whats most trouble free sytem for fuel tank and vent as said i have hard tank 600 ml bought from model boat shop think it was dubro and it has three brass tubes on it one for clunk and fuel to engine,as mentioned my clunk is on about 3 inches of fuel so its free to move , other for fuel in which i have connected to gas fill connection point and third is vent just siliconed out of the way to top of hull to get air to tank

When I first started in boats I ran clunks in the tanks and I never had good luck with them. In my opinion a rigid piece of brass tubing going the bottom of the transom end/port side of the tank is the best setup. My favorite tank system is by far an IV bag though. No vents, no fill lines, no return lines. One line to the carburetor with a "T" fitting inline with it to be used for filling the bag. Very trouble-free.

I think what Ed is describing is using an IV bag on the end of the vent line. Start with a full tank and IV bag full of air. As the fuel is drawn from the tank, air for venting the tank will be drawn from the bag. When refilling the tank the air will be pushed back into the IV bag. Sounds like a good setup to me if you really want to keep the hard tank. This would provide a good venting method without allowing any water into the tank in the event of a blow over.

marc wrote:


That's the system Marc , I still like a hard tank but I'm trying a IV bag at the present time in my Lazer 45. Jury is still out. The nice thing is that the vent bag can be placed anywhere in the hull with no balance problems and the hard tank keeps the fuel weight in a smaller footprint which does not move the balance point with fuel usage as much as a IV bag with a larger footprint does. Also I have the same amount of fuel in the hard tank each time I start a heat. This is not as critical on the Lazer as it was on the Hurricane. Be shure that the fuel line and the tank stopper are rated for GASOLINE and not silicone glow motor stuff.

thanks marc for all your info think im going to change to a bag setup ,have seen a IV bag advertised at my local boat hobby shop as im in australia ,where its summer now !!!,but there bags are intrevenous bags cleaned and flushed is this normal ??,where is site i can get from in us and what is normal size as IV seems small only 300 ml ,what sought of run time with a zenoah ,as im only sport baoter not racing THANKS