zellos 48g issues

Bought this boat about 8 months ago, finally took it out 2 weeks ago to break it in (weather it needs it or not is unclear in man.) Runs for 15 min ok then dies, almost impossible to get it going after this. Did the exact same thing 4 times on 2 separate outings. After the last time I had the boat back in the truck and decided to check the gas, upon opening the gas tank you could hear a Pssss--- it had a vacuum in the tank. The one way valve air valve on the tank lid was not working. Nipped off a bit of valve just so you could see crack----Problem solved. Next issue, approx. 21/2 tanks on it and you can not get past 1/3 throttle or it just boggs down and will die, if you let off the gas and keep it at 1/3 (approx. 15mph) it will go forever. When you first take off it goes like a bullet for the first 50 feet then bogs down. Slow idle at 1 turn and the fast anywere from 7/8 to 1 3/4 does not make much diff. Checked fuel lines fuel filter. Next issue Muffler noticed that almost no water was coming out of the muffler cooling port on side of boat (motor port has good flow) Brought home and hooked to water pump and ran engine,90% of water comes out of tail pipe. Is this designed this way or do I have a lemon? Also auto sinkers (bailers) let 10x more water in than out. Any insight into these problems would be appreciated. I have 2 other Zenoah motors in my 1/5 trucks and they run flawless. This boat is possessed!

Change the diaphragm on the carb throw some 5 min epoxy in the auto balers keep us posted

really

You shouldn't have water coming out of the exhaust unless the water out is plumbed into the end of the exhaust for silencing. Some pics may help.

No mods this is stock zelos 48g, water just goes in and out of the cooling ring. Did not know if there was a hole on the inside of the muffler to cool the rest of it. Could not find any info on the mfflerAttachment 166000Attachment 166001Attachment 166002