Finally got the boat in the water Saturday, tach was DOA. I've been running a MSD distributor, 6m2l ignition box, blaster2 coil, and an 8920 tach adapter for the last 12-13 years without a problem (well, except for 2 blown boxes, a couple of dizzy caps and pickup replacement.) Boat runs fine, no wiring problems (as far as I can tell.) Substituted a known good ignition box (I carry a spare for obvious reasons)- still no tach. Pulled the tach and hooked up an automotive dwell-tach- still nothing. Pretty much got it narrowed down to a bad VDO tach (doubtful) or a bad 8920 adapter (more likely.) Just wondering if anyone here has experienced 8920 failures. Now's ONE time I wish I had a twin engine boat... Thanks in advance for any input.

Well, MSD strikes again- turns out the 8920 tach adapter took a dump. Actually, I'm glad it turned out to not be the tach (box is much easier to find and probably cheaper than a 25 year old VDO tach.) If the MSD stuff didn't work so damn well (when it works) I don't think anybody would use it. I'm running a big cam and fat carb, and can idle for hours in the 6 knot zone without a single misfire. Oh well, on to the next disaster...

I have an 8920 to sell. Only used for about 15 minutes. Found out I didn't need it for my application

Why do people keep buying MSD's?

Many Schit Daily

Sadder part is, most that drop a grand on them don't even need them. And then many can't afford the parts they really could have used....better carb or exhaust or prop..... I run into this a ton in the car/truck world too.