Fuel starvation problems, 79 Merc 70 hp

dorsett59

Seaman Apprentice
Joined
Jun 4, 2008
Messages
49
I was having some issues last year with water getting into the lower unit. It's a complicated fix (20-something seals and gaskets), so I took it to a shop for them to do the work this spring.
Well, I got it back, they told me they did the work, and "pressure tested it."
Since then, the motor does not run right.
I took it out this last weekend for the first time. Fuel was 3 gallons of fresh, three gallons of stabilized leftover fuel. I spent the afternoon in a no-wake river. Lots of idling, but no issues.
Later in the day, I took it out onto Lake Michigan, and the thing just would not wind out. It would bog out and die when I increased throttle. I adjusted the carb settings I could get to, and managed to get it to 2500 rpm, well below the 5300 it did last year.
So, when I got it out of the water, I took it back to the garage, and reset the carbs to work as well as a I could without a run tank.
I took it back out last night, brought a can of new fuel, and a replacement fuel line/bulb.
Same issues. Started okay, but the engine would barely run over 1200 rpm. anything over high idle, and it would bog down and die. Adjusted the carbn, and was able to get back to 2500 rpm, but nothing more than that. After running 30 seconds at that, it would start to bog down again. Swapped out old fuel for new, same result. At this point, I noticed the bulb was getting very soft.
Tried running it again with me manually pumping the bulb. It kept the boat at 2500 rpm, but not any higher.
Looked at the fuel filter/screen, and that was fime. Hoses to/from the fuel pump are old, but are holding pressure. I'll need to replace them, but I don't think they are an issue at this point.

Any ideas? Would "pressure testing" the lower unit damage the fuel pump diaphragm?
Thanks in advance.
 
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