View Full Version : 2001 50 Mercruiser Throttle problem
"The motor lags or sometime stalls when I go from idle to full throttle, for pulling a skier. We have tried to have the problem diagnosed, but the mechanics seem to jerk us around by saying that they fixed it, or don't know what the problem is. What could be causing this?"
"Injected or carb? What service has been do to this motor? Has all of the scheduled service been done and is the gas clean/fresh?
Any popping sound when you hit the throttle? Is it due for a tune-up? Is the flame arrestor clean?
Look at the fuel system first, then ignition. Also, look for a different mechanic."
Thanks for the response. I dont't know everything about this motor, because it belongs to inlaws. We use it alot, so would like to get it fixed. The motor is fuel injected. The tune-ups have been done, supposedly. I haven't heard any popping, and the flame arrestor is clean. I will have to go back and check to make sure all the service has been done. I am wondering if the fuel system is the problem. If it's not in the fuel system, then would it be related to timing or maybe something else? Thanks again."
"Is this surging happening near 3000 RPM?
Look at the fuel system. The majority of driveability issues are fuel related. Look at the spray pattern (if it's TBI) by removing the flame arrestor. It should be cone shaped at all times. You should also check the fuel pressure and there may be a fitting with a black cap on the fuel rail. The cap covers a Shrader valve (same as a tire valve) and this is where the pressure is checked. You need to see about 30 pounds at this valve. Check it at key ON, idle, 2000 RPM and WOT. My guess is a clogged fuel filter or loaded fuel/water separator. Also, look at the fuel tank vent fitting and make sure it's not clogged. If the fuel pump is on the side of the motor, it has a screen on the inlet at the bottom. Remove the fuel line and look up into the pump's inlet for anything that could be blocking the screen. If the tank has run dry more than once, the pump's impeller may have problems. Never run it dry. Add gas when it shows 1/4 tank and make sure the fuel is dry (no water).
If you decide to buy a fuel pressure gauge, go to Sears and get he one with the relief valve and clear vinyl hose on it. The valve gets rid of air in the gauge (gives you a more accurate reading) and makes it easy to take a fuel sample. Let the gas go itno a clean, clear container and let it sit. The gas may be cloudy and if this is the case, you will see water droplets settling out. If the gas looks dark, it may be from Sta-Bil being added or it may be old gas. If the gas is reformulated, it starts going bad in about 3 weeks and the ethanol mixes with water so you will generally have a milky layer at the bottom. If you check this out and it still surges, remove the distributor cap and look at the terminals. If they and the rotor are fuzzed up, use a wire brush to clean them and try it again.
Make sure the spark plugs are good and are gapped correctly.
Also, make sure the fuel line from the tnak to the fuel pump isn't kinked or being crimped by something laying on it. There have also been cases where a specific run of fuel line needed replacement because of internal de-lamination."
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