Had similar prob

did fuel pump,  no diff

if you have a fuel connection at the motor   check the non return valve is not blocking fuel supply

it is on the engine side

i pissed the connection off all together and ran the fuel hose straight in to a T piece

no more prob

Hi I own the 115 Mercury that does not throttle up. I did rebuild the fuel pump, and the day I took it back on the Lake it ran the best it has for a long time,I thought my problem was fixed I was so happy.I took it out today and the same problem was back. The only thing I did was gas it up.

                                                               Any Idea's           Thanks for any help          Terry Lamos

hi terry

im sure you are trying everything and it gets very frustrating

is the tank breathing ok ?  did you check those fuel connections

its soungs like fuel supply

disconnect and eliminate every section from tank to carbies after that im stuffed

My Johnson 150 has the same problem, getting progessivly worse over the past two season. We have replace all external hoses, buld and now have gone to an external fuel tank. All to no avail. This year it was professionally severviced, mechanic provided a clean bill of health, note; using the external tank he test ran before I took her home. Yesterday I ran it before leaving for the ramp. Boats in, starts right up, idles nicely. As soon as I trottled up she dies, what a day.

Any suggestion? Thanks PSN

Patrick:

You may be running a little too lean on the midrange circuit.  Often a really smooth idle (too lean) will show up as a stumble when accelerating.  No offense to whoever tested it in the tank, but you cannot tune it up in the shop, it must be tuned on the water.  Try opening the idle screw (s) on the carbs 1/4 turn and see if it still stumbles.  High speed jets are not adjustable so no problem there.

Thanks for the info on the idle screws, After I replaced the fuel line and reconfigired the filter she runs much better, must have had an air leak? If she dosen't clear up I'll try the low idle screws.

Thanks Again

Hi Gents,

 same problem in South Africa if you leave old fuel in the tank (crap quality) Mine is autolube. Best thing is to run carbs dry by removing fuel line, if you are not going to use your motor for a while. To solve the issue, remove carbs and strip down. Wash parts in benzene or thinners to clean and reassemble. Our fuel here goes almost like a shallac and gums up jets etc. Worked for me.

If in doubt - flay out !!!!!!

exactly... take Grant Hardings advice.. the wonderful fuel product we are getting these days is just superb(sarcasm) unfortunately potatoes and corn dont store to well in the vented atmosphere of your float bowl. therefore stop being lazy and take it all apart. carbs all the way to the reed plate. clean everything. this winter when you store your boat.  or even this summer if its going to be parked for more than 30 days, drain the fuel out of your system.. a couple easy ways with a two stroke is to simply disconnect the fuel while you have it running on the trailor post your final load for the day/ weekend/ month. etc. .. keep the motor running after disconnecting the fuel use your hot start lever or if you have manual control capabilities(i.e. quicksilver merc remotes ) run up the rpm's over 1k 1.5k and when it starts to run out of fuel and die use your choke in short bursts to keep the motor running.. if you hold it for to long it will die.. if you dont hold it long enough it will die... youl get the hang of it..  make sure you get it all out...  even then a small layer of lacker will build up over time..  probly need to drop the bowls and clean carbs again in three seasons.. maybe four