1995 Tracker/Mercury 40 HP Bogs Down Under Load as Day Heats Up

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reedcbr

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Apr 23, 2018
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I have a 1995 Tracker/Mercury 40 HP that runs well early in the morning. However, as the day heats up, when I put it to full throttle the engine bogs down. It still runs but roughly and only at about 1/2 power. If I tilt/trim the engine up while under load it will rev up to high RPM and then if I trim/tilt it back, it will run fine until I throttle down or re-start. If I shift to neutral and throttle up, it revs up just fine. So the problem seems to be under load. The engine starts with no problem.every time. I bought the boat used, earlier this year I've tried the following to try: Drained all fuel and re-filled with Non-ethanol (with seafoam additive), Changed the fuel line and primer bulb, replaced fuel filter. Sure would like to figure this one out without taking to the shop. Any ideas would be a big help.
 
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reedcbr

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Joined
Apr 23, 2018
Messages
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Ok, finally had a chance to test this and still have the same problem. Even tried opening up another 1/4 turn
 
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reedcbr

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Apr 23, 2018
Messages
8
Update: Ran Seafoam (1 gallon gas/ 1 can seafoam) through gas line into motor and also sprayed into carbs. Smoked like hell but seemed to run much better after that especially after changing the spark plus. However, once again, as the day heated up (~ 85-90 degrees) the engine would not get up to full throttle (~5,000 rpm) until I trimmed the motor up quite a bit. Once I tilt it up, it comes up to full throttle and will stay there after I trim the motor back down. Hoever, If I have to back off the throttle or put it in neutral, it happens all over again. I also ran a compression test on the cylinders with all plugs out. The compression reads 55-60 psi on all for cylinders. Sure wish I could get this figured out....so frustrating. Maybe try CDI next?
 
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