Depth data (Prostar 197)

[jercrane]

My buddy and I did some experiments this weekend with my boat and I thought I’d share the data. We did the experiments because I haven’t really found this info anywhere else on here or Mastercraft forum.

 

I’m on a lake in NH where knowing depth is pretty important. I’ve always kind of wondered how to think about depth readings and when it’s ok to do what.

 

This is all for a 2009 MC Prostar 197

 

Experiment 1: straight static measurement of draft

- buddy in water with mask and measure stick

- Me in boat, full tank of gas, a few skis, 4-5 jackets, anchor, a few other random bits of gear. Not a lot though

- Calm lake

25 inch from surface to tip of bottom prop blade

 

Experiment 2: hole shot

- rigged a pvc pipe with two balls on either end attached to poly line strung through pipe and set to allow pipe to sit at depth of 4 feet. This served as reference point for driver above and swimmer below.

- Buddy in water with mask and measure stick sitting just outside a buoy

- Me driving same boat with same load

- Started at about 10 feet from buoys at idle

- Buddy dove under as I began idle run

- When the tip of bow crossed the plane I went full throttle

- Ran this one two times to confirm measurements

32 inches from surface to prop tip on pass 1

34 inches from surface to prop tip on pass 2

(Super sketchy I have to admit, even though I could see my buddy the whole time and made sure he was on driver side)

 

Here’s my buddy waiting for me to come back and pick him up. :D

 

Experiment 3: depth gauge measurements.

- both of us in boat for this one

- 10 foot pole with increments of 2 inches marked out.

- Pole placed in water at roughly halfway between the engine box and swim platform

- Pole measured actual depth of water at 9’8”

- Depth gauge (MC factory) measured 8.6 feet or roughly 8’ 7”

Depth gauge delta = 13” negative. Meaning the actual depth from surface is 13” more than the gauge reads. We verified this at several depths and it was consistent.

 

So the two take away from all of this ...

 

If I subtract 1 foot from depth gauge reading that is my actual clearance from bottom of prop.

 

If I am in 3 feet of smooth bottom water I technically will be fine pulling out of the hole. In all practically I’m going to add an extra 6 inches to this in my head.

 

Hope this is sort of helpful to someone else.

 

 

 

[Jmoski]

Some depth finders allow you to input an "offset" to account for the fact that the puck/sounder that's glued to the bottom of the boat is usually below the waterline.

[JC McCavit]

@jercrane - what is the advertised draft in your boats specifications?

[jercrane]

@JC McCavit Mastercraft says 27” for bareboat.