Thunderbolt Ignition sensor

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I just want to share an experience I had recently with my 2002 248LS Mercruiser 350 with Bravo 3 drive.

 

I was putting into Lake Michigan in Portage and right after the launch, the engine would not start. I quickly determined that there was no spark. Long story short...it was the pick-up sensor in the distributor. I picked up the new part and replaced the faulty one. The sensor uses a hall effect transistor and a magnet to sense when to fire the coil. In the old part, the transistor leads are exposed and showed obvious signs of corrosion along with an exposed circuit board. The new part was all sealed with silicone or epoxy.

 

This same thing happened to my brother-in-law's boat (Baja with twin 454's) when we were a mile offshore. Luckily he had 2 engines so we were able to get back to port.

 

So, how does this help you? First, If you have an older boat, you should find out if you have the Thunderbolt Ignition. Then see if you have the newer sealed unit. I do not know what year Mercruiser switched to the newer part: #87-892150Q02. If you have the old part (take it out and look underneath), you should swap in a newer one. I was able to get one for $50 locally. It was easy to install in about 30 mins. I also changed the rotor and cap too.

 

For $50, it is definitely better than having to get a tow.