Bad Tach or Possible Motor Problem

[WVU FAN]

I have a 1998 21 Wellcraft dual console with a 1998 Johnson 150 Ocean Runner. The other day, in the "no wake" zone I was running at approx 1000rpm, like normal. Boat felt like it was going slower than normal at that rpm. After the "no wake" I accelerated, and the tach went up to 6000 very quickly. The engine was not racing, and I was only going approximately 12mph. Boat felt like it was dragging through the water. Wake behind boat looked odd as well. This boat is new to me so I am not totally familiar with it yet. Of course every imaginable problem goes through my head. Shortly, the r's go down to 1500, I speed up and the boat trims out at about 4000rpm and approx 30mph, which what the boat has been doing prior to this problem. <br />The boat is in my backyard right now and the tach is stuck at 2000rpm. I am assuming the problem the other day was the tach was gooofy, and <br />I wasn't thinking too clearly.<br /><br />Should I assume the tach is bad and replace it? Best type? Is it possible that there is another problem and the tach is only related with it.<br /><br />If I replace the tach, do I have to replace the wiring, or are there contacts on the back of the gauge and the wires can be removed from the old tach, and used with the new tach.<br /><br />Thanks for your help.

 

[Solittle]

Re: Bad Tach or Possible Motor Problem

First thing is to remove all the wires to the tach and clean meticulously & reattach in case the problem is a bad connection.<br /><br />If that does not do it check out the charging system as the tach is fed by it. I would suspect that the problem is not with the tach itself but I'm less than a whizz with anything electical - I can change a light bulb though.

 

[angus63]

Re: Bad Tach or Possible Motor Problem

WVU <br />Welcome<br />Is it possible that you had a bunch of weed wrapped up in your prop? Possibly a plastic bag? The syptoms you explained are what happens when this occurs and the weeds or debris eventually break up and the problem goes away. <br />Also, the tach will sit at variuos positions when you shut down. As long as it "zeroes" next time you turn the key it should be okay.<br />If it occurs again, you can stop and raise the motor to confirm. I usually give the motor a quick shot in reverse after I leave my weedy canal before accelerating.<br />Good luck

 

[Seasport]

Re: Bad Tach or Possible Motor Problem

Do you think the motor actually went up to 6000rpms? You should check that you haven't spun the hub inside your prop. This would cause the motor to spin without the prop going as fast. Could be slipping which would explain the erratic behaviour.<br /><br />Doesn't explain the tach stuck at 2000rpm though. Does it go back to 0 when you turn the ignition on?

 

[WVU FAN]

Re: Bad Tach or Possible Motor Problem

Originally posted by Seasport:<br /> Do you think the motor actually went up to 6000rpms? You should check that you haven't spun the hub inside your prop. This would cause the motor to spin without the prop going as fast. Could be slipping which would explain the erratic behaviour.<br /><br />Doesn't explain the tach stuck at 2000rpm though. Does it go back to 0 when you turn the ignition on?

 

[Silvertip]

Re: Bad Tach or Possible Motor Problem

Electronic gauges very often are of a "float" design. In other words, they don't necessarily go to zero when the ignition is turned off. The gas gauge on your car is another example. However, it should pop to zero when the ignition is turned to the run position.