Motor Woes Continue

Carl

Carl

Well-known member
Staff member
Got the boat out this weekend to do some fishing and see how the 25 Merc ran after I cleaned the carb.
Previously, it had been idling fine but would bog down under load when trying to get up to speed to get on plane.

Saturday morning, she cranked right up and then jumped right up on plane! For about 1/2 mile.
Then the motor bogged down and puttered along for a few minutes. Then jumped up on plane again for a hundred yards or so. T
hen bogged down, would not like to even get about in-gear idle. This continued all morning.
On the way back to the ramp, it then ran 1/2 mile with no issues.
Seems to me like the needle or float is sticking/unsticking randomly, starving the carb of fuel & then refilling.
Or the fuel pump is randomly not delivering enough fuel.
Any thoughts??
I'm leaning towards another carb cleaning & a fuel pump rebuild.
 
A friend had similar issues with his kicker, also a Mercury on his brand new Lund Mr. Pike. Have you done anything with the supply line, particularly did you replace it or the pressure bulb? Kareem eventually found a piece of plastic inside the bulb just large enough to mostly impede fuel flow to the motor...why it kept happening intermittently. Just another thing to cross-off.
 
Have to check all those little things. After all the work I did on my motor this summer, I had it out and it was sluggish, I was like WTF?!?!?!?!?!? I had changed out the hose ends and the spring on valve of the new hose end was not strong enough to open the valve of the tank pick up. I messed with it and the pick up valve was bad and would stay slightly open and was very hard to fully open.
 
Carl said:
I'm leaning towards another carb cleaning & a fuel pump rebuild.
Click to expand...

From what you had reported before it did not sound like you had done a complete carb teardown and cleaning. (just removed the bowl, sprayed the internals and blew with air) If there is a blockage behind the needle or trapped behind a jet, a complete teardown usually is required to clear the entire carb.

As has been said intermittent blockage could be in the tank pick up, at the primer bulb check valves, at the fuel pump, or at the carb. A blockage if often associated with an intermittent fuel delivery because the foreign object(s) are free to move about within the confined space where they are trapped. The main thing you need to determine is what type of contaminants and where did they originate? Dirty fuel? fuel hose breaking down? primer bulb breaking down? fuel line between pump and carb breaking down?
 
Just replaced the bulb and fuel line a month ago after all this started.
 
Some one else suggested a bad coil, hadn't thought about that. It ran good first thing and then after sitting at anchor for 2 hours. Might be onto something.
 
I did remove the needle, clean it & spray all the openings well.
But I did not remove the jets.
No sign of water or junk in the filter.
I will check the pickup again.
I think my fuel lines breaking down is where the original gunk came from.
 
Never thought about the pickup valve on the tank. Sonething else to check.
 
Watching another rebuild video, I might have put my float in upside down. Will check this weekend.
 
Carl said:
Watching another rebuild video, I might have put my float in upside down. Will check this weekend.
Click to expand...

Please report back on that. Never done something like that, myself. [whistle]
 
I had a new fuel line from west marine go bad from ethenol gas. The inner liner came loose. Do you have a extra long gas line, friend put bulb near tank [ in bow], had to move close to motor. Did you paint the motor and mask off the air intake?
 
Cap vent open? I know, dumb thing to post but I know someone who had similar problems who didn't vent the cap. Problem solved
 
Sometimes idling on the hose the coil will be fine but under heat and load they act up. I used a hair dryer once to "warm" them up. Take a fuel sample in a glass or clear plastic jar as well. I had a fuel tank was fine under the deck but once out in the open rain got in.
 
I have a heat gun, after I check the float, I may try to heat the coils and see what happens.

Gas is good, I emptied the tank into a clean bucket a month ago, cleaned and dried the tank & pickup and replaced the fuel line & bulb. A full can of seafoam went in as well.
 
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