Tachometer Problem

[CapCrunch]

I have a 2005 Bayliner 192 with MerCruiser 3.0 engine which has 27 hours and is in second season. On the third time out this season, the Tach needle started bouncing back and forth between 3000 and roughly 4200 RPMs. The engine did not surge and all other instruments showed OK. This happened after I had cruised for about an hour at between 2800 and 3200 RPMs and then was at dead slow (about 800 RPMs) for about 25 minutes. After a while, the Tach would appear to be normal, then bounce around some more. This pattern continued until I pulled the boat from water. Everything appears to be operating OK, but I don't know if I have a potential problem.<br /><br />Any help appreciated.

 

[ahein]

Re: Tachometer Problem

Bad ground on the tach only? Loose tach wire at the coil?

 

[ccfarm5]

Re: Tachometer Problem

Cap, <br />Did you find a fix for your problem? I have a 97 Mercruiser 5.7L doing exactly the same thing, except now it is accompanied by occasional misfire. I haven't tried checking the ground on the tach, but I am about to replace the coil out of frustration. Please let me know if you found a cure.

 

[Mischief Managed]

Re: Tachometer Problem

There's usually a 4,6,8 cylinder select switch on the back of the tach. Move it through all its positions a few times to clean the contacts and then put it back to its original setting. Usually does the trick.<br /><br />ccfarm5, Your problem is likely more complex if the engine is missing. There's alosmt no way the tach can cause a misfire so the flakey tach is likely a symptom of another problem. First place I'd look is the main wiring harness connector on your engine. It's cylindrical and black. Usually on the starboard side. They tend to loosen up with use, especially in rough water.

 

[ron7000]

Re: Tachometer Problem

There's alosmt no way the tach can cause a misfire

I've had bad tachometers before, they can manifest themselves in various ways including misfires.<br />Before you go replacing the ignition coil or any other parts before you are sure, just disconnect the wire going from the back of the tach usually marked 'sender' to the negative side of the coil. It's this connection which can ground out the coil constantly, thru the tach, causing problems. Your tach won't work with this wire removed, it'll sit at zero, but if you no longer have misfires when running then you've most likely pinpointed your problem before buying/replacing parts. You will of course have to guess, or know by ear, what rpm you're running at when cruising. I would also not replace the coil until you have a new cap and rotor, spark plug wires and spark plugs, especially if any of these are old.<br /><br />with the bouncing tach needle it's probably due to condensation inside the gauge if not a bad wire connection, which is more or less normal for boats. My boat sits in the water uncovered and the tach will ocassionally read 2000 when I know it's idling at 1000, and read 1000 rpm higher than it should till I run it high enough and long till the gauge clears it self out. Also try turning on the gauge lights to burn out any condensation.

 

[THE BEEF]

Re: Tachometer Problem

I had a problem, samething tach would not read right.
Pulled old noise suppressor off coil and turned selector switch back and forth a few times now it reads fine.
Thanks BEEF

 

[ccfarm5]

Re: Tachometer Problem

Thanks for the suggestions, and I tightened up the main wiring harness connector, checked for loose connections at the tach, and ran the switch through the 4,6,8 settings. I took it out again last weekend, and it ran perfectly again from cold, but after a good run, and then a rest in a cove for about 20 minutes, I tried to take the kids tubing and it started all over again. Tach jumps from 3000 to pegged, and back again, and the engine bogs, and misfires at speed. Idles fine, though. I didn't get a chance to take the sender wire off of the tach and try it without because I found more problems! Maybe unrelated, but for some reason the heat riser on the starboard side is considerably hotter than the one on the port side (can't rest my hand on it hot) so now I'm wondering if overheating is causing the misfire?? The temp guage is not showing anything above 175, because I found that it's stuck! Boats are fun!!!

 

[Dawson96caliber1]

Re: Tachometer Problem

Thanks for the suggestions, and I tightened up the main wiring harness connector, checked for loose connections at the tach, and ran the switch through the 4,6,8 settings. I took it out again last weekend, and it ran perfectly again from cold, but after a good run, and then a rest in a cove for about 20 minutes, I tried to take the kids tubing and it started all over again. Tach jumps from 3000 to pegged, and back again, and the engine bogs, and misfires at speed. Idles fine, though. I didn't get a chance to take the sender wire off of the tach and try it without because I found more problems! Maybe unrelated, but for some reason the heat riser on the starboard side is considerably hotter than the one on the port side (can't rest my hand on it hot) so now I'm wondering if overheating is causing the misfire?? The temp guage is not showing anything above 175, because I found that it's stuck! Boats are fun!!!

Hey dude I know its been years but did you every figure out the issue that you are having my boat is doing the exact same things its driving me insane still hope you go on here any help or ideas are much appreciated! Btw its a 96 caliber 1 5.7l v8 i.0. fuel injected T.B./ replaced almost everything ignition wise!

 

[GA_Boater]

Hey dude I know its been years but did you every figure out the issue that you are having my boat is doing the exact same things its driving me insane still hope you go on here any help or ideas are much appreciated! Btw its a 96 caliber 1 5.7l v8 i.0. fuel injected T.B./ replaced almost everything ignition wise!

Hey dude, 13 years ago was the last visit by the other dude. Start a thread of your own.

Closed.