tach works till 2k RPM then dies.

[MAW31]

motor: 1986 110 evinrude. (first time out on this motor after powerhead swap)

its the oddest thing. The tack works fine and consistant through about 2000 RPM, then the needle drops off to zero.

When slowing down again, the tach pops up right around 2000 RPM and follows the RPM down to idle.

I cannot think of a scenario to explain this behavior...

anyone got any inkling what the cause may be?

thanks

 

[psteurer]

Re: tach works till 2k RPM then dies.

Could be a simple as a loose wire or corroded terminal. Try the simple things first: go to the back of the tach and clean all the wire connectors.

Your tach runs off of your alternator. You could have a problem there or with the rectifier or voltage regulator. Make sure you have everything wired correctly after your rebuild. It could be that when the engine reaches the higher rpm, there is higher vibration and some electrical connection is being broken.

 

[MAW31]

Re: tach works till 2k RPM then slowly drops off as throttle increases

Re: tach works till 2k RPM then slowly drops off as throttle increases

all connections cleaned, charge shows +13, tach works at low rpms, so rectifier has got to be working there.

The thing is, its reliable. while slowly increasing rpm at close to 1800 RPM, the needle slowly drops down to nothing over the next couple hundred RPM of increase.

then, if i back off the throttle slowly back down into that range, the needle begins to register an RPM and works with precision once again all the way down to idle.

the question is, what electrical situation could explain this behavior.

 

[big boat little motor]

Re: tach works till 2k RPM then dies.

I had this exact behaviour last year with my 1989 88spl and also noticed that the battery would discharge if I ran the motor for a while. The root cause of this was a rectifier that was dying on me and with a replacement it worked great. YMMV but that is what I found.

Jason

 

[Joe Reeves]

Re: tach works till 2k RPM then dies.

At the electrical terminal strip of the engine, the GRAY wire leading FROM the engine harness is the wire that connects to the tachometer's sensor terminal.

Remove that GRAY wire temporarily and connect it to one of the YELLOW wire terminals that leads to the stator. There are two yellow wires, you may need to try both.

If the tachometer now functions perfectly, the rectifier, or water cooled voltage regulator/rectifier if so equipped, is faulty. If the tachometer still malfunctions, the tach is faulty.