1988 Searay Seville w/Mercury V135 Engine Problems

[Mob135]

First ran boat this year after being stowed for a year. Went out on the water and engine begain to surge, and pick-up always random. First I checked fuel filter/replaced, also last year installed new coils and spark test was good. New fuel pump, cleaned/rebuilt carbs w/new gaskets, replaced old metal reeds with boyesen 2/stage reeds/w new gaskets, also new intake gasket torqued to spec. Same thing is still happening and getting worse, now air seem to blow out consciously on one side of the intake not sure where? The float levels are exact at 1/16th to spec. Boat now smokes more and still randomly surges and if at a dead stop to full throttle slowly creeps up? Why?

 

[CharlieB]

Re: 1988 Searay Seville w/Mercury V135 Engine Problems

"air seem to blow out consciously on one side of the intake"

??????????

Blown gasket or crack in the intake.

Either case, it is a serious problem, if air is blown ouot then air may be leaking IN, causing one or more cyls to run LEAN.

This MUST BE repaired before cyl/piston damage occurs.

LIGHTLY Spray a flammable fluid (carb cleaner, WD, etc) along the case mating surfaces while running at idle to see if there is any change in idle speed indicating a leak. Then spray along all intake and carb gasket mounts, careful NOT to spray so hard that it gets sucked down the carbs and causes a change in RPM.

Find and repair any leaks.

Then

Return to square one, troubleshoot from the beginning

Compression test
Spark test
Clean fuel system, from the in-tank pickup tube thru and including the carbs.

Remember that idle mixtures must be rich enough to accelerate, which is best idle in gear on the water PLUS a little more fuel.