jumping tach

[ferg57]

after replaceing stator #174-9710K1 & reg-reticifer #194-5279 on a 1995 90 hp force. then a new 1000 cca interstate battery. i go to the lake, boat cranks an runs fine but tach needle jumps from 200 to 1000 rpm at random- yet motor still runs at a steady rpm. charging system showing a steady 12.4 volts as shown on my depth finder. boat ran like this for 5 days THEN on last day of the trip, ignition switch would not energize starter, yet i could turn key in the on position an jump between large terminals on starter selniod- boat would crank an run fine but show it was charging at 13.9 volts constant. my question is what could be making my tach jump like it does, an also what could cause my charging system to charge at such high voltage.could it be the ignition switch, it is the push to choke type. any help you can give would be greatly apprecited.

 

[puddle jumper]

Re: jumping tach

It sounds like you have a bad connection. If in the beginning if you were only getting 12.4 you were only getting battery voltage. A 13.9 voltage reading is a more correct reading for a charging system to charge properly.

 

[chitownborn]

Re: jumping tach

i had the exact same problem on my 85 hp it was a loose ground wire on the rectifier, check your wiring on your rectifier to make sure there all good and tight good luck don

 

[ferg57]

Re: jumping tach

thanks gentleman for the speedy reply ,tested the starter soleinoid last night as the merc engine specific manuel said to- tested bad- took it off of the boat and hooked it to a battery with jumper cables,seemed to work just fine, iam going to clean all grounds an try again. can you tell me-- if all electric power is off--IE-- ignition,raido,fish finder--no power draw what so ever,should you still get a small spark when reattaching either positive or negitive cables to your battery, mine sparkes which makes me think i may have a short some where. and which should be disconnected first,+or- does it matter. thank you for your help.

 

[puddle jumper]

Re: jumping tach

If you are getting a small spark when hooking up your battery that can be normal. A spark at the battery when hoking it up can also mean you have a draw on your battery (not a short). A night switch is a good way to deal with the power draw when your boat is not in use.
When removing your battery clamps always unhook you negitive battery clamp first and when your hooking it back up install the negitive clamp last. This makes it safer from grounding out the wrench when tightening the clamps.

 

[chitownborn]

Re: jumping tach

ferg, just a thought does your radio have a digital clock? if it does even with the radio off the clock part of the radio will still require power causing that sparkle your talking about good luck

 

[bertthedefender]

Re: jumping tach

I seem to remember when changing the rectifier on my 1991 70hp force with a rapair 5279 rectifier, the instructions do say that it does use a small amount of current even when the engine is off, resulting in a small spark when reconnecting the battery leads.

 

[ferg57]

Re: jumping tach

thank all of you for your help will try to start working out my problems this weekend.i belive everyone should ownat least one boat in there lifetime if for no other reason than to teach a man how to be humble,an cuss real well.