Merc 90 four stroke "surging"

(Follow on to boat bottom paint thread)

Same boat I am looking at buying, has a 90HP Mercury four stroke (2006?) - motor runs smooth until it gets up around full throttle. Then it starts to “surge”… loses power, surges, then loses it again… Happens around 4000 rpm+ range. Pumping the priming bulb seems to help a LITTLE - not much. There is an aftermarket fuel-water separator in the fuel line that I suspect may have some contributing factor.

Thoughts?

I AM taking it to a Merc repair guy near me for a goin’ over…


2002 Duracraft 1548 - Mercury 25 2-stroke - and a paddle

sounds like a fuel restriction
just got to find it

www.teamcharlestonmarine.com
www.joinrfa.org

Had a motor do that exact same thing and it was fuel restriction

Mike
12’ Jon boat twin 300 Verados