Mercury 70 hp bogs down at full throttle.

Ethanol based fuel is always suspect in my book. I've had good luck cleaning low and medium speed carburetor fuel circuts by adding Chevron Techron additive to the fuel. Don't get the carb-injector cleaner with Techron. Get the 20 (?) ounce bottle of Techron additive.
The engines that bog after a few seconds at high throttle settings may have fuel starvation issues. I've heard of salt building up around the fuel line in tight places choking off the supply.

 

Fuel filters replace . fuel cap try it without the fuel cap on, change the fuel pump, check the auto choke bimetal spring is adjusted correctly.

See how you go with that, try one at a time.

 

i will try that thank you ,, i'm surprised that only under load it happens it starts up with a tap of the key cold or hot and i rev it up still nothing this is my first boat now i know why they say(B)rake (o)ut (A)nother (T)housand

 

How old is the fuel?

 

fuel is fresh 2 weeks old with star-tron ethanol buster

 

I think there is a little fuel stainer on the feed pipe on the carb, clean it.

I am assuming it is fuel as it runs ok up to a certain RPM then hasnt enough fuel to go more.

I am also assuming you know enough to check the prop for damage and that at one time the engine ran ok. If you have just bought it and its never ran properly well thats gonna be different.

 

thanks frosty the prop is new and so is the engine im going to clean out the filter on the carb and install a new water separator filter in it is slowly getting worse maybe there's crap in the tank that i pulled up i will be taking her out Thursday i hope that's all it was,,, i will let you know what happens thanks again for your input we need more people like you

 

and does any body know what was the stock size prop that came with my boat Chris craft Amerosport 230 1988 right now im using a 15 1/2 x 17 pitch im just curious what came with that boat

 

clogged fuel filter in the carb/ that's what it was thank you

 

clogged fuel filter in carb thank you