1969 Merc 500 took a swim, now no spark??

Well it was a really good storm, boat frayed thru the mooring ropes and ended up on the rocks. Hull is fixable with some fiberglass, but motor got rocked off and ended up completely submerged for about 12 hours. 1969 Merc 500 4 cyl Thunderbolt ignition.

Drained water from carb and gas lines. Pulled the plugs to drain the cyl. Surpisingly, the starter worked so I spun the engine with plugs out to clean water out of the engine. Right after I did that, I had this fuzzy recall that someone said you should never turn it over with the plugs not grounded to the engine, or it will blow something..... well guess what, there is no spark at all. So my question is, what blows if you turn it over with the plugs not grounded?

Also, what parts of the ignition system could have been blown from the little underwater swim?

All help and troubleshooting is greatly appreciated!!!!!
Thank you!

Re: 1969 Merc 500 took a swim, now no spark??

I had this fuzzy recall that someone said you should never turn it over with the plugs not grounded to the engine, or it will blow something.

Click to expand...

Old wifes tale....The distributor is full of water, pull and drain it and spray out with a water displacing spray like WD40

Re: 1969 Merc 500 took a swim, now no spark??

Thanks Admiral FAZ. I'm going to try that this afternoon. I'm not an expert, and am a little leary about tearing into all the Thunderbolt ignition and stuff on that old Merc..... any pointers and stuff I should know?
Thanks!
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