mercury verado 150 2009

by Jim Lyons
(McCormick, SC)

I have two challenges one is in regard to propping and the other is engine faltering.

I have a Harris 22 foot tritoon Sunliner. it came with a 17P prop and I could get 30 +/- mph. The problem was WOT was only about 4400 RPM and I have read that this is 'lugging' the Verado. I am trying lower P props but seem to be losing speed. at 14P I have WOT of about 5500 going to try a 12P but have lost about 5 mph
Comments?

My engine related issue is stalling/surging. Most of the time I run at about 3500 rpm at as I open the the throttle then rpm increases but then falls back. I can repeat this and eventually get to a stable WOT. I changed the screw in fuel filter which did not look clogged.

Then the problem got worse. Now the engine shakes and misfires at idle and through the range up to 3000 rpm and then will not go above 3000.

Someone suggested the plugs as suspect but I do not see how changing the fuel filter could cause a spark malfunction??

Supposed there is a second water separator somewhere but neither my manual or anything I can find shows it. All I see is the screw in with the water sensor.

Comments?