73 mercury 650 3 cyl. bogging loss of power

dogyerf21

Recruit
Joined
Apr 18, 2009
Messages
4
I have a 1973 mercury 650 3 cyl. two-stroke. I had it running great after messing with it for two full seasons. I did carb clean,Idle adjustment, link sync, replaced most of the ignition system, impeller, new L.U. seals and this motor was running like a champ. The problem: I have had this boat out four times this year and it ran great. The fifth time, it started right up, idled great, but after about a minute on-plane the motor started to slowly bog down. It was if i backed it down to half throttle. I checked the fuel filter, the throttle cable, the butterflys, and i also pumped the primer bulb while it was doing this and nothing seemed to make any difference. The problem seemed to get worse. By the end of the trip the motor was only running at about 1/4 of the power it should have at WOT. I took it home checked spark on all three, that was good. Checked compression and had almost identical 120 psi on all three. Im looking for some direction here as I'm running out of patience with this motor. It sounds to me like a fuel problem but i'm not sure where to start. The fuel pump is old but when i pumped the bulb it made no difference. The fuel tank has a vent on the cap b/c it leaks when it sloshes around. When I had the carbs apart last year everything looked great so i readjusted the floats and didnt replace anything. I do recall last year that one of the floats would hang up after being tilted all the way up then back down. I would tap on it and that would fix it. I would really appreciate any insight on this issue. Thanks in advance, Jason K.
 
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