CONTINUOUSWAVE

I have really enjoyed our 1991 Outrage 17. We are running a new Yamaha 90 and are very pleased with performance.

One problem: the boat sort stalls at certain points.

Does the stalling have to do with the fuel tank capacity?

I read [somewhere] posts on the 1990 Outrage having a problem [stalling] when [the level in the fuel tank] gets below 1/2-FULL.

[Do you think the cause of the Yamaha 90 engine stalling is due to the level of fuel in the tank being below 1/2-FULL]?
.

Should not matter what the gauge says. depends on what is left in the tank.

What exactly happens?

And what is the remedy?

An engine stall could be caused by lack of fuel.

Lack of fuel could be caused by a problem in the fuel hose rigging.

Use the fuel hose primer bulb as a diagnostic tool. Read my article in REFERENCE

A Primer on Primers
http://continuouswave.com/whaler/reference/primer.html

Another test: temporarily insert a short section of clear hose in the fuel supply near the engine. Observe the flow of fuel in the clear hose, looking for air bubbles in the fuel at the engine.

A problem with the fuel pick-up fitting in the fuel tank could also cause the behavior you describe. If the fuel pick-up tube is not long enough to get to the bottom of the tank, the fuel supply to the engine could become erratic as the tank level drops.

You should make a calibration of the fuel tank level gauge by running the tank to as near empty as possible, then re-filling to full while observing the tank level gauge and noting the fuel volume added at each 1/8th tank level graduation.

Another possible cause: there is an obstruction in the fuel system that caused fuel delivery to the engine to decrease as the tank level drops. The vertical lift of fuel to the engine increases as the tank level drops. The fuel lift pump may be unable to pull fuel up to the engine. A common cause of this is an absence of the tank vent working. Check the fuel tank vent. Determine if the tank vent is open and unobstructed.

The lack of tank venting will cause the fuel line suction (negative pressure) to increase, and it is possible that the fuel lift pump just cannot overcome the increased suction of the sealed tank. Check this as the first item. Look for a mud wasp nest on the tank vent. If the tank vent is integral with the tank fill inlet, there could be a problem there.

Please detail what "stalls" means. RPM falls, drops, shuts off, stutters, shakes? At what points? Can you make it happen? If so what do you do to reproduce.

How many hours on the engine.

I would take it back to the dealer and have them assess. They were the last to touch the boat.