50 HP Mercury 2-stroke losing power at wide open throttle
Had an almost exact same problem with 1990's 15 hp 2 cycle johnson. Lost power at 3/4 to full power and would stall. This was a first time new problem. The motor had always run great previous. Noticed small gas leak at hose to engine connector. Replaced all gas line and bulb and connectors from portable gas tank to engine. Problem solved, runs like brand new. Hoses, connectors, bulbs, check valves and gaskets just wear out over time. Simple and not to expensive of a fix.
Good luck, Shellfish
Your fuel line might be coming apart from the inside because of the ethanol in the gas. I had that problem before. The gas line looks great but on the inside is where the problem is. See of you could borrow a take and a hose from somebody and give that a try.. I use Mercury quick clean in my motor a little goes a long way.. Don't over do it.Hard to tell a man Folllow the directions.. Is that a Oil injector motor if so might want to check your oil level and make sure the lid is tight..
I know what you're saying...
I've manually closed my vent while transporting the tank, and when I opened it there was pressure.
The vented gas caps act as a check valve of sorts...
When a negative pressure is present, the cap has a flapper that opens to allow air in - under a neutral pressure the flapper is closed.
I would imagine a positive pressure would would likely press against the seat (flapper) causing it to seal. That is why (in my opinion) a manual vent is the way to go - nothing to break. Without a vented outboard tank you'll experience intermittent engine shut-downs, and the bulb mysteriously imploding phenomenon lol
PLMK , You may be right but I'm still doubtfull because when I take the cap off sometimes there is alot of preasure in the tank. Especially on hot days when the tank is getting low on gas? If it were vented this wouldn't be happening.
You likely had a self venting cap and did not realize it - they are fairly common.
Pumping the bulb simply gets the fuel to the fuel pump when the motor is not running so the engine can start. After the engine starts, the fuel pump takes over and sucks gas from the tank. If the tank is not vented, the engine will starve for gas and quit. I had an old tank with a self venting cap that did not work, I had to loosen the cap while the motor was running or it would starve for fuel and quit.
not saying he is wrong, but not all motors run on a vented system. My 50 Evenrude [2 stroke] is a sealed system. Tanks dont even have a vent. Some of the newer tanks have that to relieve the preasure on hot days when your lower on gas levels,but run on a sealed system. Google your motor for factory recommendations. Good luck
The vent on the gas tank you are referring to should always be open. It is a similar concept to sucking on a straw, if you put your finger over the other end the suction stops. If you remove your finger it returns. The vent on the tank has to stay open or you will starve the motor for fuel.
The leak I am referring to is after the tank, in the hose, bulb, or fuel line downstream. If you pump your bulb and it does not stay firm - you have an air leak, or a bad check valve in the bulb. Since you replaced the bulb already, your issue is likely between the bulb and the fuel pump.