I can't say about your exact tach but every auto/boat/motorcycle tach I have
worked on gets a pulse (ac) signal from the ignition module and translates
the number of pulses into rpm. The ignition control doesn't convert
anything. It's already dealing in pulses. On the back of aftermarket tachs
there is a selector switch so it knows how many pulses consitute a full
revolution of the crank. You never said if both tachs went at the same
time? That would suggest something other than the tachs or ignition modules
since the chances of two of them breaking at once is odd. In 9 cases out 10
if the ignition is still firing the problem is the tach if it's not a wiring
issue. Obviously you want to make sure it's not a wiring issue before you
buy a tach. Generally the biggest single electrical issue on boats is
faulty or poor connections due to corrosion. Even terminal blocks have
trouble. I solder and heat shrink all my wire connections. On terminal
blocks I use stainless steel inside star lock washers between lugs. Like
these http://www.stanleyind.com/product/washer/itooth.html

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Thanks for the tips I'll check for manufacturers, and you're right it
may be a throttle linkage issue. Both throttles work- just the one of
them wont stay in position. I guess its whatever in the linkage
tensions the cable?


As for the tachs- are you sure the signal is a/c? As an elecrtical
engineer myself, I'd be very surprized. I suspect the Ignition control
unit converts the frequency to voltage. I don't think a guage would
usually have the ability to translate a frequency into an analog value
(meter position). By maybe so! I dont have a scope so if that's the
case Im screwed!

Spy