Tach problem or other?????

[brian.white66]

I purchased a 1980 bayliner 17" with a 140 mercruiser, motor runs fine, I'm using a 14.5 x 21p prop in good shape, the problem I'm having is the performance of the boat for the most part is poor, won't run over 25-27mph most of the time regardles of the load with the exception of one trip this summer I took by myself and the boat ran well, I got her up to 33-34mph at 4600-4700rpms, right now I wandering if it might just be in the Tach itself, when I turn the key on the tach needle jumps to around 3000 and stays there and I believe this a indicator of potential problems, some input from more knowledgle people would be nice before I begin to tackle on my own, oh and one last thought could this be a spun hub issue.

 

[brian.white66]

Re: Tach problem or other?????

Should I rephrase my question, come on people a little input would be nice.

 

[Boatin Bob]

Re: Tach problem or other?????

Get a portable tach and attach it to the coil and see what it says, also disconnect the wire for your tach incase it's causing the problem.

 

[rickdb1boat]

Re: Tach problem or other?????

Brian, the Tach. should zero with the key in the ON position. Below is a link to troubleshooting it. But even if the Tach. is off, it still would not affect performance. You will need to repair the Tach. problem and get accurate WOT readings before prop advice is given. You would recognize a spun hub pretty easily, as it would rev up but the boat would move very slowly. This is most evident at take-off. Hopefully others will chime in and offer more advice. Performance can be affected by many things though..

http://ww2.tflx.com/pdf/stdign~1.pdf

 

[brian.white66]

Re: Tach problem or other?????

Thanks for the input, right now I'm guessing it's not a spun hub issue as the hole shot is fine but that once it starts to plane out I cannot run WOT, I have to run about 3/4 throttle which in turns gets the rpm's down around 4600 at about 25mph which I know that speed is not correct, On one trip I believe the tach worked fine as I could run WOT at 4600-4800 rpm's with a speed of 33-35mph and I belive that is about where this boat should be.

When I turn the key on the needle on the tach does jump to around 3000 and stays there with movement back and forth, I'll try the portable tach soon and see what that gets me, oh and also the idle speed is about 1200 rpm's which I Believe is high but may just be that the tach is not working properly.