Motor Problem 90hp Mercury

[brisboats]

I can rope start my Merc 150's as long as it is lined up on the backside of the compression stroke. Might be a case of a weak starter or a weak arm or a rusted crank, sticking rings. Take the plugs out spray some pb blaster in each hole and turn the flywheel by hand you should be able to decipher each bump of compression for each hole motr should turn easily. If the motor feels tight and binding doing this ..rut roh. If not I would revisit the weak starter and arm.

B

[Kracker Jack]

Try starting it with a little juice behind it on a boost setting on your b attery charger that should rule out weak battery. My 135 does the same thing to me with a fresh charged battery. Im thinking the starter is pooping out on me or like Ridge said it could be bad cables (corrosion inside sheathing createing resistance

[Hedge]

Have the heads have been shaved and there's too much compression?