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Discussion Starter · #1 ·
Ok I have a 06 Merc 4 Stroke 115, It only has maybe 170 hours on it. My problem is that this weekend, When I was running it, every time I would trim my motor, or move my jack plate up or down, I would loose 100-200 RPMS. My volt meter would show 13.6 then I would hit one of the switches, and the volt meter would read like 11.6. The batteries are brand new. If anyone has a simple explanation. I would be happy to hear it. This is the first four stroke, I have ever had, but I have to believe that this is not normal. Also I ned some suggestions on where to have a cover made for my boat. Either in NW Houston, or DFW area.
 

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My dad had a similar problem and we figured out we had too many accessories running off the single factory lead so we doubled up the wires and it pretty much quit. You could also have a slight ground out somewhere. It is normal to see a drop in voltage when you add a big current draw like the trim or jackplate. As for the lost rpm's, it sounds like the current draw may be lugging down your alternator causing you to loose engine rpm's. Also, make sure your battery terminals are making a good and tight connection.
 

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The rpms are not really going down, just showing it on the tach from too much voltage draw, the engine has two sets of winding, in the stator, or for charging , and one for running the engine, voltage to the cdi box to fire the engine,.
True if running acc. off the key switch it will pull too much amps on the 16 ga. battery + wire,
 

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Discussion Starter · #5 ·
Thanks a bunch. I thought that it might either be too small of wires, or dirty/loose terminals. Especially since the only accessory I have is a GPS. I am going to clean the battery terminals, and tighten the lugs. I think I will check the connections at my fuse block and clean them also, just too rule them out.
 

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Discussion Starter · #6 ·
Sonnysmarine said:
The rpms are not really going down, just showing it on the tach from too much voltage draw, the engine has two sets of winding, in the stator, or for charging , and one for running the engine, voltage to the cdi box to fire the engine,.
True if running acc. off the key switch it will pull too much amps on the 16 ga. battery + wire,
I understand what you are saying, but I was running WOT and trimmed the motor, and could actually feel the drop in speed. I then proceeded to watch the tach as I did it again, and thats when I noticed the RPM drop on the gauge itself. My GPS is running off of my Fuse Block. It is old, and probably needs some maint.
 

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If trimming under Could understand the drop in RPM more load on prop, if trimming out, then something is not right,,, but not a Merc Cert, Mechanic,, work on a lot of the older ones, This one is a Yamamerc. Most likely, but can not hook the Yamaha computer system in this motor,,, Most of the 4 stroke mercs were Yamaha's Power heads, untill Mecr Sued Yamaha for Dummping motors on the Market, which Yamaha Won the case, and Stopped selling powerheads to Merc.
 

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Discussion Starter · #8 ·
Yeah I Don't know either. I had a noticeable drop in speed from the trim or Jack plate in either direction on both. It has to be some sore of impedance problem right?
 
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