1979 90 Merc Thunderbolt slow to start.

[Nordyfloats]

I have a 90 horse power 1979 Merc Thunderbolt outboard that is slow to start at the begining of each day. Early last season the motor turned over fine, then all the sudden when i would try to start I turn the key, and there is a 5 to 10 second delay in the motor actually turning over. It sounds like the starter weak and it takes it that long to slowly starting turning the motor over. As I keep the key turned it starts turning over faster and faster and always starts.

This is only a problem when the motor is cold and on the first start up of the day. After that, a simple bump of the key starts her right up.

I thought I may have a low cold cranking amp issue from my deep cycle battery that is two years old, but this year I added a second battery to the system, isolating a starting battery, with over 700 cranking amps. I took the boat out this weekend for the first run of the season and had the same issues (slow to turn over) at the dock.

I am thinking my starter is just weak, and possibly going bad. Is there a way to clean or anything else I should try before I replace it?

Thanks for your time.

 

[Chris1956]

Re: 1979 90 Merc Thunderbolt slow to start.

Clean up the battery cable ends. Also, inspect the battery cables end to end, looking for bulges. The bulges are corrosion, under the insulation.

Check the quick disconnect plug for corrosion as well. A voltage drop test at the starter and starter solenoid primary winding will tell you where to look for the problem. If the voltage is good, disassemble the starter and clean the commutator and inspect the brushes. Replacement brushes are avail.