7.5 won't go full throttle

[Rude55]

I have a 1980 7.5hp that will idle fine and will run fine except when you start to give it gas , it won't go to full speed I'll just start to bog down , Iv changed spark plugs , fuel lines , cleaned the carb twice , it's also a new gas tank.

[phillnjack]

check the timing, check the plugs, if ngk throw them in the bin.
cleaned the carbs hey !!!! did you soak them in carb cleaner a few hours and then take out the little freeze plug and then blow out every hole with high pressure airline ?
if not then you did not clean the carbs.

Now also check the float level and check that the float itself has not got a pin hole in it .


phill

[Rude55]

Hey I did everything you said and just took it out and it will still do the same thing but every once in awhile when you have it full throttle it'll random kick to full speed and perfect but as soon as the slow down and try again it dosent throttle up again .

[RedNeckDeluxe]

Check the plug gaps,play with the throttle in a rapid motion. It's not the fuel tank but it could be an air leak in any of the fuel lines. Also mess around with the throttle and choke inside the motor (while it's running)to see if there's a sweet spot while your out on the water with the throttle on full bore position

[Rude55]

i tried that out yesterday on the water with no luck. how would you test for a fuel pump?

[PtownBubba]

Sorry to jump into thread, but my 2000 50HP is doing the same exact thing,,,, starts, idles, yet under load, no power or rpm,,also it does not vibrate or shake, so I did not think it was only hitting on one cylinder, symptoms seems just like your deal,,,,,

I also was pumping fuel line bulb while it was acting up, thinking that would help a weak or failing fuel pump,,, pumping bulb did nothing.
pulled plugs, looked wet,,, 120 compression on cylinders
was told it may be the stator acting up,,,,,, any thoughts about that ?

Again sorry to butt in,,, but different motors with the same illness could have the same cure.

[Rude55]

How would you go about testing the stator and the symptoms of a bad one?

[PtownBubba]

well,,, found the problem,,,, boy did I mess up,by not detecting this right away,,,,,I installed a new 11 gal fuel tank,,,, and it seems the cap on the new tank was not venting,,, the vent screw was not all the way in, or all the way out, but, it seemed awful tight,, ran it in and out,,,, never got "wiggly loose",,,, so I removed it and made my own cap vent system,,, took boat to river it ran fine,,,,,,,,,,,,,,, so it was a fuel issue all along.

So Rude, check that, park boat in sun for a while,,, then remove gas cap,,, if it blows or hisses at you,,, you vent is plugged,,,,,