nitro tach

[yoggii]

I just got a 1991 nitro 115 evenrude in great condition,only thing that dont work is the tach.when you turn on switch needle on tach backs up a little but thats all it does.it dont move when motor running...i am a mechanic so i should be able to fix this if someone will give me some pointers on what and how to check..thanks!!

 

[etracer68]

Re: nitro tach

I would first check, that the motor is charging the battery. The tach gets its signal from the REC/REG, most likley a gray color wire. If its not charging (13.5+volts), then the tach, is NOT getting a signal. If it IS charging, then I would say, check connections on the tach, and rotate the pulse selection dial on back of tach, and reset to correct number. I think on the 115 HP 4cyl, the pulse should be set to 6. Also may want to try a known good OB tach. 4 stroke motors get signal from the coil, 2 stroke from REC/REG. My.002 opinon, im sure others will give theres also.

 

[tazrig]

Re: nitro tach

I would first check, that the motor is charging the battery. The tach gets its signal from the REC/REG, most likley a gray color wire. If its not charging (13.5+volts), then the tach, is NOT getting a signal. If it IS charging, then I would say, check connections on the tach, and rotate the pulse selection dial on back of tach, and reset to correct number. I think on the 115 HP 4cyl, the pulse should be set to 6. Also may want to try a known good OB tach. 4 stroke motors get signal from the coil, 2 stroke from REC/REG. My.002 opinon, im sure others will give theres also.

Good advice. I would also check the tach wire all the way back to either the REC/REG or the coil and check the connections there as well. If that doesn't work try running a jumper wire from the tach to the coil or REC/REG directly to the tach as well as making sure you have a good ground. Sometimes in wiring from that vintage can either be pinched, corroded or broken under the insulation where you can't see it. I've had many wires that looked perfect on my boat but would work. When I run the jumper suddenly the problem goes away.

 

[yoggii]

Re: nitro tach

I looked at the motor when i got home today.Looks like rec/reg is the flat one under the back of the flywheel,it has 2 yellow,red,purple and gray wires going into connector.Tomorow I will run wire from gray connector to tach..How do I check to make sure it is charging?I dont have a meter..Thanks for the help!!!

 

[tazrig]

Re: nitro tach

How do I check to make sure it is charging?I dont have a meter..Thanks for the help!!!

You can always touch the neg wire with one finger and the pos wire with a finger from your other hand... JUST KIDDING!!!!!!! A much less painful way is just go buy a multi meter. Walmart, radio shack, harbor freight or any auto parts store have them for around $10-30. It's a very handy tool to have.

 

[yoggii]

Re: nitro tach

I actually knew a man once that would hold one wire with his hand and touch the other wire with his tongue,even on 110 ac.I saw him put his finger in a spark plug wire and touch his tongue to the fender brace and fire jumped from his tongue. anyway I guess im going to wallmart to get a meter..thanks!! So I crank motor and check for 13.6 volts or should I check voltage first before cranking???

 

[etracer68]

Re: nitro tach

Wow, I would like to see that. First, set the meter to DC VOLTS @ 0 to 20, then touch the black, and red lead to the battery posts (red to +, and black to -) while the motor is NOT running, you should see about 12.2 to 12.4, on a good charged up battery. Then start the motor with water ears, while it is running check again with meter, and you should see about 13.5 volts, if its charging, if not, it will only show the same as before starting the motor, or under a bit. You can by-pass the REC/REG by following these instructions.

http://forums.iboats.com/engine-fre...ed-regulator-rectifier-joe-reeves-190636.html
Yes, the rect shaped box under the back of the flywheel is the REC/REG. If it shows bad, you will have to remove the flywheel to get clearance to replace it. You may want to start a thread in the Johnson and Evinrude section for better answers. Also, I would get yourself an factory service manual for your motor, not a seloc or others.

 

[yoggii]

Re: nitro tach

ok,just checked with meter and meter stayed same with motor at high idle,,about 12.43 ..How do I remove the flywheel to remove reg.??Do I have to have a puller and are they marks to put back in the right place???thanks again for the help!!

 

[tazrig]

Re: nitro tach

You'll need a flywheel puller to take it off of the crankshaft. When you go to put it back on you'll see a key in the crankshaft with a matching slit in the flywheel. Line them up then re-install flywheel.

 

[yoggii]

Re: nitro tach

ok,I didnt have the tools to remove the flywheel so I took it to a friends shop,Marks marine in wahala sc.. When I get the tach fixed and get my rpm I will be getting a ss prop.What prop would be good for a 17 ft nitro bass boat with a 115 rude??Make? 3 or 4 blade?

 

[Silvertip]

Re: nitro tach

Until you get your tach fixed you have no idea if the prop you currently have is in the ballpark or not. You then go to the prop forum and look at the READ THIS FIRST info to determine what's needed for prop selection.

 

[tazrig]

Re: nitro tach

You might also find this helpful:


Propeller Tutorials - Propeller Pitch

 

[yoggii]

Re: nitro tach

got tach fixed,19 pitch 3 blade alluminum turning 5300 rpm,poor hole shot with just me..im thinking maybe 4 blade ss 18 pitch,,any thoughts????

 

[NYBo]

Re: nitro tach

How big is the boat? A 19" should provide a reasonably good hole shot unless the boat is overweight. Is the prop in good shape? Are you starting off with the motor trimmed all the way down?

 

[yoggii]

Re: nitro tach

17 ft nitro bass boat,yes motor is all the way down,prop is in good shape,im thinking 18 pitch 4 blade will get rpms to around 55 or 5600 with just me and improve hole shot.shouldi go ss or i hear the new solas alluminumis as good as ss?

 

[NYBo]

Re: nitro tach

You should have a reasonably good hole shot with your current setup. It sounds like the motor isn't putting out full power and/or you've got waterlogged foam adding a bunch of weight.