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Merc 80 hp bogging down

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Kubie

New member
I have a 78 80hp merc that really starts well in hot or cold weather and when on plane, runs excellent.
The problem is when trying to accelerate from idle to take off. If I move the throttle to fast, the engine dies. I can move it slowly, it will pick up enough rpm to finally take off.
I've taken it to my local merc shop and they cannot duplicate the problem using their water tank. They tell me that the motor is strong and has good compression.
I'm thinking that because of the age of the motor, the carbs should be gone through.
What do you think?
 
guyjg said:
SN please. 3, 4, or 6 cylinder? Get a mechanic to go on the water w/you. Does it have an accelerator pump?
Click to expand...

I don't know if it has an accelerator pump but will find out. It is a 4 cylinder. I don't have the SN.# handy.
They offered a mechanic to meet me on the water, but the cost is quite high. If I do that and the carbs need rebuilding, thats close to $1000.
Thanks for the response!
Kubie
 
Try this: Get a can of SeaFoam or equivalent Gumout product. With the engine in the run position disconnect the fuel line at the tank and stick it into the can and pump it into the carbs w/the squeeze ball. Let the engine sit there and soak for 24-48 hrs. Then fire it up and run it at 1500 RPM...it will smoke like it's on fire until the SeaFoam burns off. The carbs will be cleaner and the engine decarboned. Throttle response will be quicker.
 
Noooo! Take a screw driver and open (turn CCW) each idle mixture screw 1/2 turn out.

Common problem with the advent of ethanol gas.

Jeff
 
I ran a can of Seafoam mixed with 16 gallons of gas when I first bought the boat. It helped with a more crisper throttle and smoother idle.

Before I pick the boat up from the shop tomorrow, I'll have them adjust the idle screws according to your instructions.

Thanks again for the quick responses. I do appreciate it.

Kubie
 
fastjeff said:
Noooo! Take a screw driver and open (turn CCW) each idle mixture screw 1/2 turn out.

Common problem with the advent of ethanol gas.

Jeff
Click to expand...

Isn't that a needless headache what the EPA & Big Gvmnt has done! Weedwackers, lawn mowers, snowblowers, and anything with an internal combustion engine has been crippled by this! I can't get at the mixture screws on my weedwacker, it is set so lean, it will only run on 1/2 choke, spewing more gas/oil mixture into the atmosphere, then if they had just left it alone!

I guess all the "corn huskers" are dancing with joy from all the subsidies! While everyone else has to suffer with crappy gas!
Where I live in Pa., near the NY, & NJ border, I haven't found a gas station yet in 3 nearby states, that just sells straight gasoline!
 
To answer some more questions, the motor does not have an accelerator pump.
It is a two carb 4 cyl motor.
I picked up the boat today and they turned the mixture screws out 1/2 turn for me.
I'll take her out, do some bass fishing and will let you know the results.
Again, a big thanks to everybody for the help.
Kubie
 
MikDee said:
Isn't that a needless headache what the EPA & Big Gvmnt has done! Weedwackers, lawn mowers, snowblowers, and anything with an internal combustion engine has been crippled by this! I can't get at the mixture screws on my weedwacker, it is set so lean, it will only run on 1/2 choke, spewing more gas/oil mixture into the atmosphere, then if they had just left it alone!

I guess all the "corn huskers" are dancing with joy from all the subsidies! While everyone else has to suffer with crappy gas!
Where I live in Pa., near the NY, & NJ border, I haven't found a gas station yet in 3 nearby states, that just sells straight gasoline!
Click to expand...

Our marina sells 100% gas and "marine gas" which is also 100% gas. Might want to check marinas instead of gas stations. Around here it only comes in 89 octane though and cost more than premium gas does.
 
fastjeff said:
Noooo! Take a screw driver and open (turn CCW) each idle mixture screw 1/2 turn out.

Common problem with the advent of ethanol gas.

Jeff
Click to expand...

Jeff-----That was it!!!!
Turned the idle mixture screws 1/2 turn out and it took care of 98% of the problem. I need to increase the idle adjustment up a bit thoughas it dies when put into gear.
Had a great day fishing yesterday. Lotsa bass and 2lb crappie.
Thanks again Jeff.
Carl
 
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