Mercruiser 260 spark problem

snoski

Seaman
Joined
Aug 23, 2008
Messages
69
I am in need of some expertise on the Thunderbolt IV Ignition System on my 1987 Wellcraft with the Mercruiser 260. First let me state what all I have done. I started with installing a new starter and ignition key switch. Then I installed a starter slave solenoid. After that the starter would turn the motor over fine but it would not fire. I inspected the distributor ignition sensor and it looked very old and brittle, so I installed a new sensor, rotor, and distributor cap. I checked the fire coming from the coil and there was none. I installed a new coil and the boat would crank and run fine.
We took the boat to the lake today and it ran really good for a total of about an hour or so, then it started skipping, and then died. After that it would not fire up and there was no spark from the coil to the distributor.
Can someone direct me in the right direction in solving this problem?

Thank you,
James
 

Don S

Honorary Moderator Emeritus
Joined
Aug 31, 2004
Messages
62,321
Re: Mercruiser 260 spark problem

Here a link to the OEM service manual you can download to your computer.
http://www-alt.mercurymarine.com/mnetdata/SERVICE/CRUISER/Servmanl/09/cover.pdf
It's almost 500 MB, hope you have broadband or cable.

This troubleshooting guide for the TBIV may help a little.

TB4troubleshooting.png
 
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