intermittent spark

So after my last crusader **** the bed. I did a repower. I bought a 305 from a 228 merc package and an alpha out drive. I have everything on and what not. When I had the engine on the stand on a "boat in a box" ( a 9 pin conn to a box with a siwtch and gauges on it) it ran beautifully. When I was putting it in I hit the distributor cap on the way in to the in to the boat and broke on of the terminals off. So i replace it . I check all the wires everything was tight but today I am getting intermittent spark on my spark tester. I have a thunderbolt iv the triangle kind. So i pulled out my tested and wen down the list. I have 12v at the coil 12 on the red/wht wire to the dist. But little or no charge going to the wht/green wire on the other side of the distributor. I took the saftey interrupt switch off to eliminate and still the same problem. So i followed the wht green back to the T-bolt iv and the grey wire coming from the - side of the coil to the t-bolt has plenty of juice but there is little of no coming back out to the green/white wire. When I put my tester on the green/wht it makes the coil click and I can feel the current go from the coil to the distrib in the coil wire. So bad T-bolt ign module is my guess what do you think?

Re: intermittent spark

what is the common cause for t-bolt's going bad?

Re: intermittent spark

I think you mean where the sparkplug wire connects to the distributor cap, the actual cap itself broke. Maybe the force of the hit was transferred to other components in the distributor. Did you replace the rotor as well as the cap? If the tip of the rotor was close to where the cap got hit it could have taken on damage as well.

Re: intermittent spark

My previous post may not be relevent, I just realized that you may be checking spark at the secondary coil terminal and the rotor would not be in the "loop".

Re: intermittent spark

yea I replaced the cap and rotor. like 3 volts coming to the green white wire at the distributor.... is this normal ?it should be 12 v yes?

Re: intermittent spark

i have been searching but i haven't found one. Is there a how to on diagnosing the ignition systems on this forum...

Re: intermittent spark

I have a thunderbolt iv the triangle kind.

Click to expand...

Ayuh,......

The Diagnostic tree would be the Same for all the V-motors that run the same vintage/ style of T-Bolt IVs....
1 of the online Merc manuals would cover that......
About the only variables would be the timing curves,+ the # of cylinders.....

Re: intermittent spark

what is the function of the white/green wire? ... I know the wht/red is the 12v source//

Re: intermittent spark

There is a black ground wire atachted to a lug {bolt}on the bottom of the dist. housing and connected to one of the module mounting bolts on the side of the port exhaust elbo. This grounds the module to the dist. if its loose you will get an intermittant spark or no spark at all. Make sure its clean and tight. If this ground wire is not there make sure that the ign. module is grounded properly or temporarily hook up a redundant ground between the module housing and the distributor housing and the engine block retest for spark. This ground circut is crucial for proper engine operation.

Re: intermittent spark

I have no ground here just two wires...

Re: intermittent spark

bad ignition sensor ... used trouble shooting manual 1b ....

Re: intermittent spark

One of the reasons why, a point distributer is better on non- FI boats.
You can carry a spare set of points, and a condenser.
Electronic costs too much to carry a spare, imagine if you were out in big swells, with the module dead.