1969 Merc 1250-interesting tach event

[JasonJ]

I have the original Airguide tach that was in the boat, reused it when I did my project. It has always seemed to work fine. Over week or so ago we had a lot of rain. The boat stays in the water for the season, and is always covered. I had a tiny bit of water come in through a repaired rip in the cover and settle in the bilge, maybe a cup or so. Last weekend I went to go fishing and the tach did not seem to work. i checked connections and they were fine. I said "screw it" and went fishing. As I was cruising along, the tach started to work, but it was a slow thing. It slowly made its way from 0 to the 4000 I was running, and seemed to work fine the rest of the day. Yesterday, I went fishing, and it worked initially, but was running at around 2000 when I knew I was at around 4000. It came back up over a period of about 5 minutes, worked fine the rest of the day. The temps have been cooler, 40s at night, 60s during the day, overcast. This has caused me to wonder if the tach is ever accurate at all. Is it possible that something is binding in the needle and is temp related, or could it solely be an electrical issue, or if this just the normal signs of a tach dying a slow death?

 

[tmcalavy]

Re: 1969 Merc 1250-interesting tach event

RIP Jason's tach. You will need a new tach soon. <br />TWM

 

[Clams Canino]

Re: 1969 Merc 1250-interesting tach event

When you get a newer tach you'll have to move the tach pickup lead from the switchbox to one yellow leg of the stator and then set it for a 12 pole stator.<br /><br />-W

 

[JasonJ]

Re: 1969 Merc 1250-interesting tach event

Thanx guys, I kinda was thinking it was dying. Hey, it lasted 35 years, not too bad. I ran it again today, in 40 degree weather, same deal. It was acting relatively normal after about 10 minutes, but I question its accuracy at this point. Even when it seems to be acting normal, it shows my idle at around 600 rpms, but the motor does not die when I put it in gear. It does sound like it is idling slow, which I don't have a problem with. It still shows all the way to 6000 rpms, but I am thinking maybe just getting a new tach would be best. I have been doing setup changes, and it would not do me any good to have an inaccurate tach.