Why wont my 50 hp mariner start ? - Mercury Gear Set, Complete, Mariner, Force Inline 4 40-50 HP Outboard

24/1 is the correct ratio. I certainly wouldn't go 50/1 but you could split the difference with a good synthetic.

1957 Johnson Seahorse QD18 10hp Oil Mixture - Marine ...

http://www.marineengine.com > showthread > 10690-1...
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1995 I believe. Here is a link to a chart - omit the leading "0".
MERCURY OUTBOARD MODEL YEAR GUIDE 40 HP 4 CYL 50 HP Mastertech Marine

Try trubleshooting with your repair manual Outboard Motors Boat Parts Marine Engines Inboard Boat Motor

Hey Mike, its either a 50 or 60 hp...
Mercury Mariner 50 60 HP 3 Cylinder Engine Components

Reverse polarity should only blow fuse,if solenoid is clicking but motor not turning then solenoid is faulty

I just looked at 7 different sites and they are saying Max RPM is between 4,500 - 5,050... How accurate is your Gauge?

Prop Pitch will greatly effect MAX RPM.

http://forums.iboats.com/mercury-mariner-outboards/wiring-diagram-pull-electric-start-mariner-20hp-1985-a-468275.html

sounds like you need to get the carburater cleaned and install a new set of spark plugs

check compression? i don't know the year but most mariners need min 100 psi and all cylinders match within 5 psi. check it when its hot. if you have low compression piston skirts are worn. they are responsible for intake and exhaust port timing. rebuild. if you have good compression through all temps check timer base. you'll need a multimeter and resistance specs. clymer manuals are great and can be purchased at your local dealer