1998 Bayliner - 120 Force questions

1998 Bayliner - 120 HP Force.<br /><br />Two quick questions, any help and/or insight is greatly appreciated.<br /><br />I have owned the boat for 3 months now and I know about what she sounds like from idle all the way up to WOT. Recently, the tachometer has been acting up. It seems to read about 1000 rpms higher than what the motor is really running at. For example, I will be cruising along at about 4000 and then it will jump to 5000 and hold there. It might come back to 4000, it might not. There is definitely no change in the sound as she still purrs along like a kitten. It also will read +1000 at idle at times also, such that it will tell me I am idling at 2000 rpms (and I know the rpms are at idle speed).<br /><br />I am just wondering if there is anything I can do to try and troubleshoot this problem? I am just being cautious as I am fairly new to this and I don't want to ignore any warning signs that something is starting to become fouled up.<br /><br />Secondly, there is a plume of water that comes up from the back starboard side when I am on plane, it does not shoot up into the boat but it plumes about half way up the motor cover. I don't seem to be losing any horsepower, but I can't imagine this is the most efficient running condition (plus it's really nerve racking). It almost looks like its orginiating from "under" the boat and then pluming up in a spray type pattern. There is a depth finder instrument(6in x 6in small box) mounted on the back-right side of that boat, but this is the only difference between the right and left sides. I don't remember this happening when I first bought the boat so I have discounted the depth finder as being the culprit.<br /><br />Any ideas as to what might be causing this plume?<br /><br />I appreciate all the help on the site. I am a chemical engineer (don't know much about mechanics) and, of course being an engineer, need to figure out every little problem and want to know everything. Without you guys, I probably would have sold it a month after I bought it because I didn't know what was going on.<br /><br />Thanks again,<br />Luke

Re: 1998 Bayliner - 120 Force questions

Is there a ladder on that side? Mine has one. check to make sure the brackets that hold it havent come loose and it slid back.