1979 Mercury 140hp bogs at WOT

[SPLMAXSAM]

My friends and I rebuilt a 1 owner great compression 1979 Mercury 140hp Tower Of Power outboard. It is the 1st generation of electric ignition. We rebuilt the carbs, replaced wiring harness, internal fuel lines, fuel pump gasket , and spark plugs. I have had the problem pretty much since splash 1/6/2016. What happens Motor starts fine after bout 5 ball squeezes and throttle advanced. Runs smooth at low and medium throttle. At wide open throttle: A) motor bogs down and eventually speeds up and then bogs back down B) fuel line and ball collapses What i have tried to resolve the issue 1) changed spark plug wires 2) removed fuel filter 3) changed fuel bulb 4) switched fuel line to non collipsible fuel line 5) open fuel fill latch to allow tank to breath better Motor still bogs. If i prime the ball when running full throttle it will run fine Assimption - starving for fuel?

 

[SPLMAXSAM]

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I am boating on 2/22/2017 and willing to try suggestions

I ran a "red gas can" above deck and the motor appeared to run at WOT. I will repeat the test again on thursday

 

[SPLMAXSAM]

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I am thinking i need to add additional tank venting? Reason bulb and fuel lines collapsed liking drinking a milkshake through a straw

 

[SPLMAXSAM]

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Under deck tank, fill line and vent line , fuel filler and vent

 

[racerone]

When the bulb collapses you have a restriction between the bulb and the pick-up inside your tank.

 

[merc850]

Unscrew the fuel tank pickup and check for a filter screen on the end, if it's dirty clean it by pumping fuel backwards or soaking. The tank might be dirty too and that inline filter might be interfering with the flow; they aren't usually installed before the fuel pump.

 

[Faztbullet]

Get rid of the anti siphon valve that appears to be in the tank withdrawal tube and loose the filter.Its harder to pull fuel thru filter than to push thru with your style fuel pump....

 

[SPLMAXSAM]

Thanks will dig down and look pick up screen

 

[jimmbo]

If the filter is very large, like a water separator filter(about the size of a Chev oil filter from the 70s) the pressure drop would be insignificant to cause issues, unless the pump was very weak. Anti-siphon valves are required by Federal Law(US) and the USCG on all permanent fuel tank installations. Some times they do stick from gum and varnish.

 

[merc850]

What is that setup in your 2nd post (motor well)? appears to be a T fitting and 2 primer bulbs which could be causing flow problems. You need 1 fuel line to 1 tank to motor.

 

[jimmbo]

What is that setup in your 2nd post (motor well)? appears to be a T fitting and 2 primer bulbs which could be causing flow problems. You need 1 fuel line to 1 tank to motor.

It looks like a line going to a kicker motor. Not the best way to feed two motors.