85' 90hp inline 6 bogging down after 1/2 throttle. HELP!

[ryanalaska1990]

okay guys im stumped on this one.

i have had this motor running just about perfect, except a little carb heng up, and i took it out today for a nice day planned on the water and everything seemed normal at first, then i pushed it up to half throttel and it seemed normal then i pushed it to full and absolutly nothing happened. as if it stayed at half throttle. so i backed off to idel and spun the boat around and tried agian. this time when i get 1/4 throttel it just bogged down and shut off.and thats all it did the rest of the time.

now this was only happening when i had it in gear. when i had it in netural it ran up to full with absolutly no problem. .

the boat does have a onboard fuel tank but i havent been using it latly. i have been using a extiror tank and i keep it on the floor of the boat with the fuel line running up and over theupper buidge to the motor.

so what are you thinking guys.. i need suggestions. i have a extra fuel pump but i dont feel thats the problem.

thanks
-Ryan

 

[Chris1956]

Re: 85' 90hp inline 6 bogging down after 1/2 throttle. HELP!

Ryan, Running a motor at high speed in neutral is often teminal for the motor.

The obvious first step is to take a compression test. The motor won't make full power if a cylinder or two is down on compression. The next test is a max spark advance test. The spec for that motor is likely 21* BTDC. So remove the #2-6 spark plugs, install then into their plug boots, tape them together and ground the plug bases. Now advance the throttle to full and install a timing light on #1 plug wire. Crank the motor and note the ign timing advance