bogging out

[deuce888]

I have a 74 merc 150 that is sucking my fuel prime ball flat after about 5 mins wide open throttle have checked vents pump screens replaced ball and tank connectors, cleaned carbs any ideas!!

 

[cwilt]

Re: bogging out

i just recently replaced my primer ball cause mine started to leak. the new ball started to do the same thing yours is, collapse on itself. it seemed unusually soft. so i bought a new one again (different manufacture). i think the rubber reacted to some fuel additive.

 

[deuce888]

Re: bogging out

i have thought about finding a stiffer ball now i will thanks for your time

 

[daveswaves]

Re: bogging out

I have a 74 merc 150 that is sucking my fuel prime ball flat after about 5 mins wide open throttle have checked vents pump screens replaced ball and tank connectors, cleaned carbs any ideas!!

Hey Deuce, I read your PM, a couple of things to look at here. Firstly if your WOT RPM is only 4500 to 5000 RPM then you are running too steep a pitch prop for this engine. Your target should be 5800. This is for the overall health and well being of your engine, the inlines do not like to lug, they like to rev.
If the engine will run at WOT for 5 minutes then the fuel pump is likely OK and capable of supplying the quantity of fuel at the pressure needed. If you can T in a fuel pressure gauge you need a minimum of 4.5 PSI at WOT to keep feeding this beast. If you are lower than that you will eventually drain the fuel bowls and your engine will bog or die out. The same thing can happen if the fuel float level is set too low.

The fact that the fuel bulb is collapsing indicates a restriction between there and the tank, too small a line, plastic seal from an oil bottle floating around the tank and blocking the intake, blocked air vent. See if you can borrow a different tank and see if it makes a difference.

 

[JimDD]

Re: bogging out

I have had this problem before and eliminated the hose/primer ball by using a separate 6 gallon tank. If after you run on the 6 gallon and the bulb does not collapse, you have eliminated the hose itself.

Your permanent tank has a vent fitting. Try to run with the fill cap cracked open only to allow vapor balance as you run. If the bulb acts properly your vent is plugged. If this does not work, next I would then look for the fine mesh wire screen at the base of the pickup tube in your permanent tank to be varnished up. Nowadays with the gasoline companies, you get a little different product specification excursion that are within EPA guidelines but sometimes these can present nuisance worries and problems such as yours. You could very well have run some gas that was rich on additives and wall washed your tank and created the pluggage.

 

[Chris1956]

Re: bogging out

If you are using a built in tank, your antisiphon valve may be dirty.