While replacing the oil pressure sender and attendant gauges on my 1982 Marine Trader 34 DC with its original 120 Lehman I pushed the "Horn Button". WOW the horn did not blow- the gauges went crazy--and a little puff of smoke came from the new VDO oil pressure gauge. OH MY MY-- now Im in trouble! Could all be ruined??? So I went outside and removed the horn. Checked the wires coming from the horn and it was a 'dead short' coming from the horn s insides. Over time the interior had corroded together and when the horn button was pushed it sent positive 12 volt electricity to all the ground wires connected to the gauges... Further investigation revealed that neither it nor the engine gauges are protected by any fuse... MY My---- well it turned out that the the gauges -old and new are ok. The horn was thrown away-the engine gauges fused. One NEVER KNOWS on these boaty's.