Let me get the obvouse out of the way, Im new to boat motors and i dont know where to start or how to proceede<br /><br /> Im using a 1974 200 20 Hp Thunderbolt ignition mercury that I got when I bought my grandfathers 13.5 foot aluminum fishing boat, I am quite sure the only matnince that has been done was a $ 150 tune up when I first got it because of the same Issue it is having right now.the tune up was done about 3 years ago.<br /><br /> I took it out today after putting in fresh gas and oil, put it in the water and started it up it only took a few pulls because I started it yesterday, and to my suprise it did the same thing, it idles ok seems smooth, I let it worm up for a minite and then put it in drive and start off up the river, I start giving it more throtle and it starts picking up speed, about 1/2 throtle and let it sit there, I feel the bubble and it seem like it is full of fuel, Good sign I guess, then not more then 2 minutes later with out notice, it is like bogging down and shaking real bad, it is only going at idle seed at this point and I didnt back off the throtle just to see if it would come out of it, at this point the buble is half water and 1/2 air, Im not sure if this is the cause because the shaking and noise the engine is making, if I back the throtle off and put and let it sit or put it in Nutral for a sec then it seems normal for a minute or two, after running it for 20 Minutes like this it just bogs down starts dieing and it's real hard to start.<br /><br /> Any Ideas where to start or what is happening,
