i have  a 17 ft tidecraft with a merc 115, has 6 in jackplate. Boat is only running 39 mph, only problem is my tach dont work.. The motor is as far down on jackplate as it will go, all of the boat isnt coming out of the water, only maybe back a foot before console is coming out. Gets on plan real good just like it wont trim up enough? Need to move my motor up right? If so how much? Anything would help thanks.

First thing I would do is get the tach fixed.

There is a small hole down near the bottom of the motor (on the "blade" looking side opposite of the prop). That hole is what reads to your speedometer.. Often this hole gets plugged with wood or other debris. 

There is a small hole down near the bottom of the motor (on the "blade" looking side opposite of the prop). That hole is what reads to your tach. Often this hole gets plugged with wood or other debris. 

I believe the small hole you're referring to is the pickup for the speedometer. In addition to a working tachometer a water pressure gauge will be a necessary addition before you start raising the engine. Good luck!

I believe the small hole you're referring to is the pickup for the speedometer. In addition to a working tachometer a water pressure gauge will be a necessary addition before you start raising the engine. Good luck!

X2

Tach and water pressure guage, don't screw with setup without them.

Is correct prop on motor?

There is a small hole down near the bottom of the motor (on the "blade" looking side opposite of the prop). That hole is what reads to your tach. Often this hole gets plugged with wood or other debris.

That definitely is not for a tachometer. That's the speedometer.

Before you mess with anything, get the Tach fixed. You could be propped wrong, motor height wrong, both, or any number of things. Fixing the Tach will instantly help you know what's happening.

That definitely is not for a tachometer. That's the speedometer.

Before you mess with anything, get the Tach fixed. You could be propped wrong, motor height wrong, both, or any number of things. Fixing the Tach will instantly help you know what's happening.

 

Wow, not sure how I missed that... My mistake. lol. Well, if you need to fix your speedometer, there ya go!

Get your tach fixed. You can't reliably tell anything unless you have a working tach. Other than that, are you sure the motor is trimming up all the way? What type of prop do you have? Aluminum or Stainless?

Another vote for fix tach first and get water pressure guage second. Then you can experiment with prop and height.