Mid 90’s mariner 75hp 3cyl bogging down.

[BigStickFishing]

Ok guys trying to help out a family member. He has a mariner 75hp motor that has been sitting for two years. When we take it to the lake it starts and runs fine. When the boat gets on plane it runs fine for a couple hundred yards then starts bogging down and comes off plane. Pull the throttle back to neutral the motor never dies clears itself out and will take off again then do the same thing. Just curious as to what else I need to look for. These are the things we have done so far.

drained and cleaned fuel tank
replaced all fuel line from tank to motor
new primer bulb
new water fuel separator
rebuilt carbs and new inline glass filter
new fuel pump diaphragm

just seeing if there is anything we over looked before we take it to a shop?

[JoshKeller]

Try a portable tank to eliminate the built in tank/lines? What happens if you keep priming the bulb while it Boggs down?

[BigStickFishing]

I try to prime the bulb when it dies and when I do the primer bulb stays collapsed.

[SilverFox579]

I try to prime the bulb when it dies and when I do the primer bulb stays collapsed.

You have a venting issue if that's happening. The bulb should be soft when running as the fuel system comes under vacuum (sucks fuel from tank), however, the bulb should not collapse.

[sooner magic]

By chance did you install the new bulb incorrect? Arrow towards motor.

[JOE54]

and what brand bulb/line try another tank line assy to eliminate boat tank and problem collapsing bulb is restriction or vent problem

[BigStickFishing]

Thank you everyone. Gonna try to find a portable tank to test run the boat this weekend.

[BigStickFishing]

Ok guys got the fuel tank issue fixed to wear now the primer bulb does not go flat on my fuel line. Got the new duke line and everything is good now. New problem is now the boat runs great for about 300 yards then Boggs down to about 2000 rpms. The motor doesn’t die then it idles good and will take off again, runs for another 300 yards and Boggs again. Will keep doing this over and over but will never stay running wot.

[JOE54]

sounds like you still got fuel restriction somewhere