84/85 mercury 50 (blue stripe) outboard low compression ....

[SarahBrown]

2 stroke merc 50, cyl 1 145pnds, cyl 2 145pnds, cly 3 145, cyl 4 115......... just traded work for this boat, tuned it up... wont stay running ... rebuilt carbs, new plugs, new wires, spark in each cyl., coils are good, fresh gas, new fuel lines, new impeller, fresh oil and seal. Help wont stay running? any ideas ??

 

[jimmbo]

Welcome to iboats
Well first of all your engine, well maybe just the cowl, can't be an 84 or 85. Brown stripes were used in 84 and 85. 1972 - 1983 were the years of Blue.

Next with one cylinder down 20% the engine will never perform to its max. It might be sticky rings and a thorough soaking of the rings with Engine Tuner and a few decarb operations might free them. Otherwise it is, pull the intake port cover off and look for scoring/scuffing, the exhaust side usually scuffs first, but it is a bigger pain to inspect. If you have access to a fibre camera, you could look at the cylinder walls to see if there is scoring.

 

[SarahBrown]

I will pull the intake port cover tomorrow ! does that require a gasket ? torque spec's for re installation ? Thank you for the info, its been rough trying to just identify this engine and get help !! the serial number is 5747308

 

[jimmbo]

Gasket yes. I would do the soak and decarb first. As for it not staying running... What is your starting procedure? Ensure tank is vented, squeeze prime bulb till firm, Set fast idle speed by disengaging shift mechanism or raising fast idle lever. Engage choke or enrichement system, Crank engine. When engine starts addition spurts of choke may be needed briefly. As engine warms up reduce speed.