Outboard Motor Help (90 HP Mercury)

[TB80]

My inlaws have a bay boat (Boston Whaler) with a 90 HP Mercury Motor. Recently when we are cruising, the motor slows down like it is about to die and then picks back up. Essentially it feels like you pull back the throttle for a few seconds and then move it forward again. We have tried putting fuel stabilizer/cleaner in it but that didn't really help.

Any suggestions/thoughts of what could be causing this and how to fix it?

[slicktricker]

Sounds almost like your bulb on the gas line not allowing enough gas at full throttle. Check or replace the line and bulb. Might be an easy fix. Also could be a float sticking in carb.

[Mayhem]

Outboard Motor Help (90 HP Mercury)

How old is the primer bulb? It could be losing prime.

Other than that, sounds like carbs to me or maybe a fuel line is starting to collapse.


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[miket]

Sounds almost like your bulb on the gas line not allowing enough gas at full throttle. Check or replace the line and bulb. Might be an easy fix. Also could be a float sticking in carb.

Yep, fuel leak, air leak, filter restricted, weak fuel pump etc. Classic symptoms of starving for fuel, keeping just enough in carb bowl/filter bowl to run good for a bit, then lag, the lag gives just enough time to fill it up enough for the next surge. Sometimes while its running if you squeeze the bulb it will pick back up and run great till it sucks it dry again.

[TB80]

Thanks guys. I'll take a look and see what I can figure out. I am no outboard motor expert, but hopefully I can figure it out.

[Leaverrite]

Check your fuel tank vent for a clog if it has one. You can crack the gas cap also to check. Don’t want to pull vacuum.

[Hammerdown]

Outboard Motor Help (90 HP Mercury)

Make sure the fuel tank vent doesn’t have a dirt dobber nest in it.


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[Razorback01]

It could be your fuel pickup in the tank itself, might have a filter screen that is clogged.