1996 Evinrude Intruder 150 losing fuel prime while setting

Motor is a 1996 Evinrude Intruder 150 Model #E150GLEDB. VRO pump with oiling function in place, WOT RPM is a little over 5,000 with 3 passengers and full tournament load, 4-blade SS prop (24P I think). This is on a 1997 Ranger with dual fuel tanks and an OEM 4-position selector switch: Port, Starboard, and 2 off positions.

The engine seems to be losing fuel prime when setting. Starting is easy and the engine seems to run smooth at idle. I can run to a spot with good acceleration and smooth running through entire throttle range. When I get to a spot and fish for a while the engine starts easy as I leave but when I hit the throttle it bogs. Re-prime the bulb until firm (several squeezes) and I can take off just fine.

My first thought is to replace the primer bulb as it might have a failed check valve. I don't smell any fuel and I don't see any sheens on the water to suggest it's leaking out. Where else should I look? Vapor tank? Carb floats and needle valves?

When I have used the Ranger fuel selector to turn off fuel when the boat is parked (engine tilted up) I have noticed the primer bulb gets sucked flat. That suggests to me that fuel is leaking out through the carbs or evaporating and that the selector switch is sealing well. Any thoughts on this?

Today I'm going to get a new primer bulb and install that. We'll see what that does for me. I would appreciate any suggestions of what else to track down as I troubleshoot.

Thanks.

Primer bulb was the problem. I had a chance yesterday to install a new one and the fuel line filled immediately and the bulb stayed firm. I put my finger over the outlet of the old bulb and squeezed and it kept no suction. The old bulb was totally shot.

Kevin... Also keep in mind the following:

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(Fuel Anti Siphon Valve)
(J. Reeves)

Many of the later OMC V/6 engines incorporate a fuel restriction warning via a vacuum device attached to the powerhead. If the engine overheats, or if you have a fuel restriction, the warning is the same.... a steady constant beep.

NOTE... Only the V/6 & V/8 engines have the above "Fuel Restriction Warning". The warning horn will not sound on the other models.

The fact that a engine is not overheating, but the warning horn sounds off with a constant steady beep, and that the rpms drop drastically would indicate that the engine is starving for fuel due to a fuel restriction. Check the built in fuel tank where the rubber fuel line attaches to the tank fitting. That fitting is in all probability a "Anti Siphon" valve which is notorious for sticking in a semi closed position. It will be aluminum, about 2" long, and the insides of it will consist of a spring, a ball, and a ball seat. If this valve exists, remove it, knock out those inner components which will convert it to a straight through fitting, then re-install it. Hopefully that cures the problem.

The above procedure will cure a restriction problem with the anti siphon valve as stated. BUT, it may also allow fuel to drain backwards to the fuel tank when the engine is not running (siphoning backwards) due to the fact that the carburetors/fuel pump etc are higher than the fuel tank. This condition is not an absolute as the valves in the fuel primer bulb usually prevent this backwards siphoning problem. However.... if this does take place, the cure would be to install a new anti siphon valve.

NOTE: There has been cases when the output valve in the fuel primer bulb would come apart, and the inner portion of the valve would actually reverse itself and be drawn back into the primer bulb's output valve body. This in effect would create a shut off valve and result in a fuel restriction. If this is the case, you should be able to feel something laying in the bottom of the primer bulb when held horizontally.

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Thanks Joe. This is on a 1997 Ranger with built-in dual 18 gallon fuel tanks. Since the fuel seems to flow back to the tanks through the failed bulb I'm going to guess there are 2 possibilities: 1) I have no anti-siphon valves or 2) both have failed. It happens when both tanks either tank is selected so I'm more inclined to think I have no anti-siphon valves.

I have a 4-position fuel tank selector switch which came from the factory. It has options for starboard, port, and 2 off positions. In the past I have put the switch in the off position and found the primer bulb sucked completely flat. My guess is fuel has left the carbs while setting in the tilted position and resulted in fuel getting pulled through up to the vapor tank.