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Indicated RPM is low

in 2 Stroke Technical Questions 7 years ago
I have a Flying Inflatable Boat FIB w/ a 582 mfg in 2004. My problem is the tach has been reading low the last few hours. I have 146 on the hobbs. Full throttle shows 5000 rpm but I am getting normal T/O power. The curve seems smooth, idle is about 2000. I replaced the tach supplied from Lockwood and same cond. I checked the grd wire and got .3 ohms. A little backround info, my charging syst went out at about 75 hrs so I purchased a lith ion battery( which saved me 10 lbs) and charge it occasionally with a compatible charger. Any idea on how to check the output of the gray tach wire? Any help would be appreciated. Thanks. Also checked wire from tach to stator .2 ohms. ohms from gray wire thru stator to grd 32 ohms.

  • Re: Indicated RPM is low

    by » 7 years ago

    The source for your Tach signal is generated by the same coils that supply the ac current to your regulator/rectifier. You either have a wiring issue or a stator that is breaking down.
      
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  • Re: Indicated RPM is low

    by » 7 years ago

    Thanks Dennis, I was afraid it was the stator, those things are ridiculously expensive compared to their PWC cousins. Since I do not need the charging circuit due to the Li Ion bat I should just run a tiny tach and be done with it.
      
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  • Re: Indicated RPM is low

    by » 7 years ago

    I have a FIB also, and the stator is nightmare . I change it at 46 hours , and I have to change it again now ( 76 hours) .. I know 2 other pilots of FIB's who sufferd same problem with their aircraft , and I suspect there are a number of other pilots who just are not aware that their stator is in bad condition just because they make one fligt and then they wait a long time before starting again . A weak stator will make the job in this condition because it always start a cold engine . ....But if you make one flight and then you land and stop the engine, the problem occurs when you need to start your "warm" engine , 15 or 3à minutes later ........your weak stator does not generate sufficient intensity when the temperature is high.....and you can never start your engine for a second flight ......... this is my experience !!!! and I would be very happy if someone could provide the solution . ( I sent a post on this specific subject earlier today ) , be free to contribut to it .
      
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  • Re: Indicated RPM is low

    by » 7 years ago

    I also had this problem. First my tach started showing less and less rpm's. Also my hour meter stopped working so I had to tap off a relay term that was hot if the master was on, I did not like that due to if I forgot to shut master I would rack up hrs, luckily never happened. Finally noticed hard to start when warm, on of the coils measured only 195 ohms, tach was at 27. I purchased a new 670 w/ all new ign. from Rotax Rick, should be running by the end of March 2019. My flying boat had 180 hrs and was built 2003. Thierry, where are you located? Are you interested in selling your boat, I have a friend who might be interested.
      
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