i have an 87 yamaha 115 etlh 2 stroke..idles great but has an obvious fuel starvation problem..when i give it throttle it'll go for a couple minutes then bog out. if the bulb is pumped while running it will run great and get to full throttle then the bulb goes flat and again bogs out. Spark tested good except questionable on two so i replaced the two coils.Compression is good,tested 130 on all cylinders.Timing was way out of whack, but good now. Has new spark plugs,primer bulb,and even put in new fuel pump as well as a new fuel line from the tank to the motor and also removed carbs and throughly cleaned them. After all this,it still has same old problem. The only thing i havent replaced is the fuel pick up. I should mention that when i bought the boat i discovered the bulb was deteriorated on the inside and had shot rubber sheds into everything but that should all be cleaned out now. The boat is an 88 starcraft 18ft deep v. Any help would be appreciated as my wife is about to ring my neck after spending 4,000 bucks on a boat that wont go fast.haha THANKS
There are only a couple things that will make your bulb go flat.
1. Gas tank not venting. Try running it without the gas cap on.
2. Debris in gas tank. At idle there is no problem because the pump isn't sucking very hard. When you give it throttle the pump sucks harder and sucks debris up agaisnt intake line causing bulb to go flat and the engine to bog down.
Make sure that the tank is well vented as noted before. Make sure that the fuel line back to the tank and forward to the engine are clear. Check the factory filter under the cowl. It lies next to the fuel pump, which by the way should be your next area to inspect. The pump is easily removable and can be disassembled to inspect the diaphrams.