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1993 Mercury 90HP 2-Stroke fuel starvation

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Ocean15

New member
First time post and thanks for any advise.
I have a 1993 Mercury 90HP on the back of my classic Boston Whaler Nauset. It seems to be having fuel starvation issues after coming off full throttle and bogs down frequently when running. While underway I pump the primer bulb and the rpms increase and it will run a few more minutes before bogging down again. Engine has new plugs, timing and compression good. I have a 9 gallon Moller tank.
Could it be a issue with the tank and a clogged fuel hose or do I have a internal engine issue with fuel pump or bad carbs?

boat engine.jpg
 
Could be all of the above, plus a plugged vent on the tank. Try running it with the cap nearly off.

Jeff
 
Appreciate the reply, I've had issues with the cap but I tried loosening it while running at high rpm - no major change, the engine still bogs down or surges any rpm's over half speed or when I pull back on the throttle. It will run smooth for about 5 minutes then start acting up. My son will pump the primer bulb every few minutes while at full rpm to keep the fuel going the engine and we can keep the engine going so I'm thinking maybe the fuel pump needs rebuilding or my fuel hose is deteriorated, I'll check both.

I haven't owned many outboards but Mercury curse continues to follow me every time I own one or use a boat with one. They seem more finicky then any other outboard make. Another discouraging boating experience on my day off. What a drag.
 
Could be a fuel pump bladder on the way out.

A whole rebuild kit for the fuel pump goes for under 25 bucks and it's a fairly easy replacement (don't need much more than a screwdriver and 1/2 hour of your time to swap the guts out).
 
Thank you Galamb,
I took the fuel pump off and took it to a Mercury repair shop - Low and behold, the valves were worn and the bladder and gasket had a problem (according to tech). I'm going to put it all back together today and see what happens.
 
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