Tachometer

[Dennis K]

One of the other small problems I am having with my boat is the tachometer will not read the correct rpm's. At idle, while going across the water at slow, medium, wot it will bounce around. I noticed Saturday at wot it bounced from 3k - 7k rpm's. Motor sounds fine. I would like to find out if the resident guru's think a new tach will fix the problem or could it possibly be another problem.



I also noticed the fuel gauge will move to read full when I am filling the livewell and move back to whatever it was reading before I started filling. I started playing with the other switches and it will do this when I hit the horn also.

The problems I am having are minor to me but I would like to get them fixed. We ended up buying the boat because the motor checked out good and ran well with no problems. And I felt like I was getting a good price. The small things I felt like I could fix.( With help/advice of course.)



Thank You,

Backlash

 

[Richard Whittemore]

Sounds like someone has wired your fuel gauge in series to a main circuit. When you start another device that devices current is passed thru the gauge. I would get the wiring diagrams for your boat and take an afternoon off with a helper and check all the wiring out. Plus repair and clean the connections as I went. The tach problem is probably a loose or dirty connection.

12, 24 and 36 volt connections in a boat are a battle to keep serviceable. Moisture, heat, dry, cold, vibration, you name it. All work adversely on electrical systems. Good Luck...

 

[Barry Loos]

I had similar problems one time and traced it to a lose ground wire under the console.



Da Bear

 

[Texas Transplant]

I would tend to agree with Da Bear. Generally, when you start having these types of electrical problems, it generally stems from a connection problem - most times the ground return.



Tex

 

[Dennis K]

Thank you for the replies. I will crawl under there and check them this weekend, as there isn't enough daylight after work. I will post back with resolution when I figure it out. Thank you fot the suggestions. I will check them out first.

Would a Hot Foot cause a problem like this? Previous owner installed one on the boat.



Backlash

 

[Craig Roberts]

Also, check the calabration dial on the back of the tach. It needs to be set for the appropriate motor. It's the small black dial on the bottom right of the picture.

 

[Bruce Freeman]

Check the ground connections first..

BF

 

[Dennis K]

I am planning on starting tomorrow. I am going to go into work early so I can leave early so I can have some daylight left to work on it. How hard is it to get the tach out. Do I need to crawl under console to get to it from behind or is there a way to get console off from the topside? I haven't looked at it that closely yet. I wanted to get the battery charger fixed first and that is done. Now to the tach.



The boat is a 1997 Nitro 640 lx.



backlash

 

[Ken Sabin]

BAD GROUND !!! Its unanimous!

 

[Dennis K]

Well for an update. I checked the connections on the back of the tach. I could move the ground wire with my fingers. I tightened it and checked the others with wrench while I was there. They turned easily also (nuts, not wires). On the water Saturday for a test. The tach still jumped some but not as bad. It bounced from 5000-6000 rpms at wot, as well at lower speeds. I didn't want to over tighten the nuts. I guess I need to go tighter. Will update after the next test.

 

[Steve Rizza]

Take the connections off and clean them up with sandpaper.