1974 mercury 1150 stalls upon fast accelleration

bassboy416

Petty Officer 3rd Class
Joined
Jul 9, 2013
Messages
79
1974 Mercury In Line 6 cylinder 115 hp 2 stroke outboard.... Boat starts (likes to be flooded) and runs great. Boat idles well and runs even better at top speed... Using Surface Gap spark plugs per recommendation of seloc service manual.... When accelerating to tow a wakeboarder, if you go from barely in gear to wide open throttle too quickly boat will die leaving wakeboarder in water.... Boat will tow wakeboarder no problem but takes a little bit of feathering for the throttle to get where it needs to be without killing the motor... Boat has always been winterized and taken care of at a marine shop... Not the end of the world, but would like to be able to pull a wakeboarder up as fast as possible without any drag... Where can I start and how hard is a complete carb rebuild on this motor? Symptoms that seem to possibly be related to this- Boat does not like to start without choke or advancing throttle after long periods of sitting, boat does not like to idle for long periods of time (but its a 2 stroke so I don't worry too much), boat seems like it loves fuel... You can't flood it (or so it seems)... Seems to love the upper RPM range..... so is this an issue that requires maintenance or is this just owning a 1974 2 stroke motor? By no means am I unhappy with the performance of this motor, it just has its quirks...
 

bcboy13

Cadet
Joined
Jul 12, 2012
Messages
20
Re: 1974 mercury 1150 stalls upon fast accelleration

Cant completely answer your question but will give my experience. I have an 1981 1150 tower of power and was having the same issue with pulling a wakeboarder up, if you hammer the throttle it bogs out and dies, but runs great overall. If your engine is running good, i.e no spark issues or anything then I suggest running a can of seafoam through the tank. Every year my engine has a bog like this until I dump and can of seafoam in the gas tank and run it through, after that no problems. I've learn to just run it through my first tank now. Anyways something to think about. good luck.
 

mr 88

Commander
Joined
Nov 3, 2010
Messages
2,111
Re: 1974 mercury 1150 stalls upon fast accelleration

Your idle jets have to be turned out. Start out by going a blade width of the screwdriver and do all three,then test.The transistion circuit is non-exsistant on these carbs[ going from low speed to high speed.] For starting issue, try priming the bulb some more after you think it is hard,basically trying to force more fuel into the system.
 
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racerone

Supreme Mariner
Joined
Dec 28, 2013
Messages
35,927
Re: 1974 mercury 1150 stalls upon fast accelleration

That motor in good condition will idle all day long , no problem.--------Try opening the low speed jets 1/8 turn at a time and see if bogging goes away.------What I have done is installed an OMC electric primer system on these.---No more cold starting problems after that procedure.
 

bassboy416

Petty Officer 3rd Class
Joined
Jul 9, 2013
Messages
79
Re: 1974 mercury 1150 stalls upon fast accelleration

Will put this to the test this weekend thank you for the advice! Extremely excouraging.
 
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