tachometer reads very high

I have a Volvo Penta 4.3GL-A. When I start the engine the tach reads very high, 4000 to 5000rpm. It stays there for a long while but usually settles to what I believe is the correct rpms. If I am idling it is between
600 and 650rpms. If I am cruising it reads about right. It is that start up reading that bothers me. I can live with it as I have for a couple years but maybe it is time to figure this abnormally out.

Its a 3 wire system... +12 and grnd @ tach and a single (usually grey) lead to the distributor. Check all connections first and then we can go from there if necessary. Some tachs have a cylinder select switch on the back ( often a screwdriver slot). Rotate it back and forth a few times. IF that fixes it you may be OK for a while, but eventually you will be looking at a new tach.

Most will do it over time. Mine does it until I knock on the dash, then it returns to normal. All my connections are tight, so it's internal in the tach and quite common, especially for older Faria tachs. I'll be replacing mine this off season along with installing a new GPS speedo. The good news is that you are not alone, and there's probably no ghost in your electrical system, although checking what Capt. Bob recommended is never a bad idea.

Thank you Capt Bob and Chris. I will check my connections in the morning and let you know what I find. The problem has been there for a while and as a matter of fact my previous boat which had a Volvo Penta 5.7GL did the same thing. If only boat engines where as reliable as auto engines

Actually they are, but they just live a waaay harder life Early in my career as an EE I worked for a couple of years as an areospace reliability engineer. Reliability for systems is calculated initially for "laboratory" conditions. Then a "k" factor is applied to correct ( degrade) to the expected "operational" reliability. The worse scenario is in a rocket, the next worse is.... "shipboard". In some ways, recreational shipboard is harsher than naval shipboard. ( Willful or ignorant abuse). ...a bit of an oversimplified description. It's also the main reason I'll never own a boat with fuel injection.

In comparison a boat engine is under a constant load. It is the same as pulling a trailer full of rocks up a mountain pass full time. When the engine is shut down you stop there is no coasting. The tach can cause engine failure do you want to chance it out there?

Sounds like boating is a lot like rocket science! I do realize that boat engines are under a constant load but it's something you don't really think about when you are out there. If you did you probably wouldn't be out there.

Checked all my wire connections today and all looked good. Started the engine and it was one of those times when the tach read 650 at idle.... or maybe just touching those wire connections fixed it... I know keep dreaming.

re: ".... or maybe just touching those wire connections fixed it.." temporarily :-(

No more like rocket surgery. Knowing how hard these engines work it is abuse if you do not perform regular maintenance schedules. Change the impeller at least every other year. Change plugs often and take spare ones out with you. Run the carb/s out of fuel between uses. Drain and refill the gearbox before winter freeze. Shoot some grease in all zerts once yearly. Clean and grease the steering cable yearly. Always store the engine in the running position so it drains completely. The less you use the engine the more often you need to do maint.