Mercury 3cyl 90hp loosing power

[wan]

Hay every body. I always find help and support in this wonderfull forum.

Please help. My 3cyl 90hp (serial# 97xxxxx) is starting when it is raised up enough gust to get water. It is speeding ok in hi gear at that posission, However, when I get it down in the water it goes and gumps well then it is losing power, and going only around 10mph and no matter what I do the speed remains the same.

Here is what I did with no use.

Cleaned and changed the carb kits by mechanic.
Treid to turn carb screws

Thanks in advance for the help.

 

[crem1]

Re: Mercury 3cyl 90hp loosing power

Check the fuel pump, then I would question the mechanic as to how well did he clean the carbs. Has to be taken off and soaked in solvent for a day with the idle screw and others taken out of the carb

 

[wan]

Re: Mercury 3cyl 90hp loosing power

Thanks for the fast response. He soaked the carbs parts on gasolin while instaling the kits. He mentioned to me that he suspects that one of the cylinders is sometimes not firing up, but I am not convinced as to why it is working ok on high gear while the engine is raised to the water level. I will check the fuel pump.

 

[sschefer]

Re: Mercury 3cyl 90hp loosing power

Raising the engine helps to releive backpressure and requires less compression and horsepower to keep a motor running smoothly. It's the same reason that a lot of engines run fine on the hose but not in the water.
I've seen engines with a cylinder down, running fine on the hose. You couldn't even tell it was down until you put the boat in the water and then they'd act just like you describe.

Get compression test done first. Read the plugs and then decide your next steps.

 

[verado7]

Re: Mercury 3cyl 90hp loosing power

we'll assume the carbs okay for now - test the ignition , if the mechanic was suspicious of it he should have just simply test it -it's not that hard to do . it does have all the sighns of igniton trouble but testing will tell and save money in the end .

 

[wan]

Re: Mercury 3cyl 90hp loosing power

Nice and thanks.

I will go step by step as advised starting with the ignition system.