Distributor replaced, now low RPM and funkly tach readings

When 1995 Mercruiser 5.7 Thunderbolt Ignition engine just stopped one day my son and I inspected distributor and rotor - contacts were badly corroded, so we replaced distributor cap and rotor and engine started right up with the new parts, but only runs slow and shows very low RPM 400 to 1200 on the tach. What should I do next?<br />Thanks,<br />Rich

Re: Distributor replaced, now low RPM and funkly tach readings

400 rpm is too low, and 1200 is too high for idle. Should be around 700 rpm. Is it surging? Is it running smooth at idle? Is it backfiring or popping? Do you have the plug wires back in the correct place on the cap?

Re: Distributor replaced, now low RPM and funkly tach readings

Hello,<br />When I bought my boat it ran terrible after the previous owner put in a new distributor.After a look it was discovered that it was put in 180 degrees off. It ran but terrible. after it was corrected it ran great.

Re: Distributor replaced, now low RPM and funkly tach readings

Just replaced cap and rotor, all wires in right place. Someone said that the sensor might be corroded as well now and to replace that. Thoughts?

Re: Distributor replaced, now low RPM and funkly tach readings

After re-reading your original post, it sounds like your engine needs a full tuneup. Not just the cap and rotor, include new sparkplugs (read the old ones as you take them out) would also be a good time to do a compression check just to confirm the engine is good enough to run. Set the timing and check the advance timing. That alone will tell you how the ign. module is doing. You can look at the connections going to the distributor sensor, if they are corroded, well, clean them up and see how it works. Same with all other connections.<br />You also need to check the plug wires. (including coil wire). <br />When was the last time the fuel filter was changed and inspected for water?? That should be a yearly item.<br />The carb will also have to have the idle mixture adjusted. The adjustment will change a bit as an engine gets older.<br />A vacuum check will also help in locating any problems. Here is a great site someone posted a few days ago on reading/interpreting a vacuum gauge reading.<br /><br /> http://users.bigpond.net.au/ergoff/vac1.htm