96 mercury 75hp rpm problems

[fishingstar]

I took out my boat for test run today and found a new problem. The tac was running about 1000 rpm high.

At idle it's 1200 and full throttle it will max the tac 6000 normal max is 5300.

The motor seems to run fine but last time out I had problems with the oil level sensor. the last time out it 

was very rough I was thinking that was the cause of the float to sink causing the alarm to sound. It has not 

came on again. Who thinks these are related?

      

Edited May 11, 2017 by fishingstar

[leech~~]

Sounds like you may be having some electrical issues. When you turn the key to on "without" starting the motor. Where is the tac sitting then. I have a 95' StarCraft with a 75 Merc and every once in a while the tac will just start jumping around but it's not the motor because it never picks up pitch and when I turn the key off some times the tac will shut off sitting at 1000.  I know that tac is old and going and it is not the motor. 

[fishingstar]

I was thinking it is in the wiring also. When I shut it off the tac has all ways stayed at 1000 when I turn the key on it beeps and the tac goes to 0.

 

 

[gunner55]

We have the same issue at times with a '02 Crestliner FH & '02 115 Yamaha. Other times it will work perfectly for extended periods of time

Edited May 11, 2017 by gunner55

[fishingstar]

Have you had oil alarm problems?

[gunner55]

We haven't

[leech~~]

58 minutes ago, fishingstar said:

Have you had oil alarm problems?

None here as well.

I would rather see the tac jump around as long as I can hear the motor running.  But oil alarms.

[AlwaysFishing23]

The wiring in the some of the older boats are dump. My dads got a 1988 crestliner and here about 8-10 years that stupid alarm would always be going off brought it in and said just do premix they took out the whole oil tank and he's done oil premix ever since works like a champ. This is a evirude 60 VRO. Just my 2 cents. If I were you that's what i would be a bit of a hassle but saves some worry.

[fishingstar]

The boat is a 97 lund pro sport. could not see any wiring issues.

that vintage of a mercury motor  96 is known to have the float get saturated with oil

and sink setting the alarm off. I think i'm good to go for the weekend   

[leech~~]

29 minutes ago, fishingstar said:

The boat is a 97 lund pro sport. could not see any wiring issues.

that vintage of a mercury motor  96 is known to have the float get saturated with oil

and sink setting the alarm off. I think i'm good to go for the weekend  

 

Is the float cork?  Guess I never really looked at mine because I keep it topped off most of the time. I hate alarms!!

[leech~~]

Now you got me worried and thinking about it!

 

Got this off a Merc repair site about the 75hp.  Were you getting beeping or just a continuous alarm?

 

"The oil tank fault is normally not a continuous beep. Continuous beep is often the oil/overheat module that combines the two sensors into one wire. Oil tank fault(blue wires) is a beep beep beep...
Serial, year and model number will get the proper drawing and confirm this." 

 

Here's a video where a guy cuts his tank in half to see how the alarm float works.

 

 

Edited May 12, 2017 by leech~~

[fishingstar]

well my alarm started going off Saturday morning. I stopped and unplugged the low oil alarm didn't help. but after sitting for two hours it didn't alarm. It didn't come back on until sunday afternoon when we were going to leave sitting in shallow water 3 feet

it started to beep then after 1/4 mile the alarms tone started to change then went away.

I had other things going on also. deep finder quit working, timer for the aerator started to buzz.

after work started looking at wiring. I found the ground strip and wires all corroded and the fuss holder was green.

I cant see that the corrosion has any thing to do with the alarm. I think they are a separate system.      

[leech~~]

You may be having low voltage issues with the corrosion showing up any where if it all on the same battery?

[fishingstar]

warning alarm has not gone off for to weeks now.

did some testing on the temp sender. decided to replace the warning module.

but it has not helped the tac I can live with the tac being off.