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My Mercury 90hp appears fine at low speeds, but when I give it throttle, the engine will pick up, then lose power, pick up again, and then lose power. Sometimes I might get 2 minutes on a plane, then it stutters back down to just above idle. So far, I have done the following to fix the problem:
a) I removed the carburetors, cleaned them, and replaced the needles (which had a lot of built-up lacquer on them. I wanted to replace the main fuel jet but didn't: My original fuel jets have a hole bored the length of the screw. The ones that came in the rebuild kit have no hole whatsoever--I don't understand how fuel is supposed to make it through. As a result, I cleaned my old jets in carb cleaner and reinserted them. Perhaps they are the problem. Can anyone explain about the jets without the hole?
b) I also suspect the fuel pump might be to blame, but decided to do a test. I put the boat on a plane and as soon as the engine started to stutter, I squeezed the primer bulb. It did not improve the performance of the engine, leading me to suspect it's something else.
c) To check the flow of fuel to the carburetors, I detached the fuel line at the entrance to the carburetors, squeezed the primer bulb, and gas comes through fine past the in-line filter.
d) My spark plugs don't look fouled.
e) It's conceivable that there's a problem between the gas tank and the primer bulb, but the primer bulb does get hard when squeezed, and fuel is flowing all the way to the carburetor.
Does anyone have any idea what is going on? I appreciate any help you can offer.
a) I removed the carburetors, cleaned them, and replaced the needles (which had a lot of built-up lacquer on them. I wanted to replace the main fuel jet but didn't: My original fuel jets have a hole bored the length of the screw. The ones that came in the rebuild kit have no hole whatsoever--I don't understand how fuel is supposed to make it through. As a result, I cleaned my old jets in carb cleaner and reinserted them. Perhaps they are the problem. Can anyone explain about the jets without the hole?
b) I also suspect the fuel pump might be to blame, but decided to do a test. I put the boat on a plane and as soon as the engine started to stutter, I squeezed the primer bulb. It did not improve the performance of the engine, leading me to suspect it's something else.
c) To check the flow of fuel to the carburetors, I detached the fuel line at the entrance to the carburetors, squeezed the primer bulb, and gas comes through fine past the in-line filter.
d) My spark plugs don't look fouled.
e) It's conceivable that there's a problem between the gas tank and the primer bulb, but the primer bulb does get hard when squeezed, and fuel is flowing all the way to the carburetor.
Does anyone have any idea what is going on? I appreciate any help you can offer.
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