How to measure prop height

[Needafunboat]

OK, silly question - but how exactly is prop height measured?

I would imagine that you extend a straight line back from the pad or bottom of the V by holding something like a yardstick or 1x2 flush along the pad/V surface to keep the correct angle.

I would also guess that you put your motor in the full up trim position (not tilt).

The measurement is where the prop shaft center is in relation to the yardstick - right?

If this is correct, my starliner appears to be running right at the bottom of the V level, which sounds high. I have no jackplate, but the motor is in the 3rd from highest holes (could still go up about another 1.5"). Motor is 25" from the top of the midsection to the propshaft.

Does this sound right, or am I doing something wrong?

 

[illMATTic]

you want to measure it at 0 trim ie motor straight up and down.

 

[Needafunboat]

Thanks Matt,

So you try to basically make the cav. plate (or propshaft) parallel to the bottom surface of the pad/V?

 

[jallen355]

Pretty much. Ideally you would have the pad/vee set level and then level the cavitation plate on the motor. Then extend the line with a "yard stick" or other straight edge towards the prop shaft. The measurement above/below is what your looking for.

Hopefully you have a h2o psi gauge which is a must before you try to raise your motor. With no setback and I'm assuming...no low water p/u, I can't really speculate where you should be. My "guess" would be that your cavitation plate would/should be approximately 1.5" above the pad.

 

[175checkmate]

The measurement is take at the center of the bullet. With the motor level 0 trim, use a straight edge on the bottom of the boat, extended back past the lower unit. Measure the distance from the straight edge to the center of the bullet on the lower unit.

 

[Needafunboat]

Thanks guys,

I'll go measure and see what I have. I won't be messing with the height for quite a while. just trying to figure out where I am, see how it handles and see what/if I need to do anything. I figure I should get the boat in the water...at least once first! The boat will be used more for watersports and family cruising than pure top speed so I won't be going nuts with motor height.

A waterpressure gauge is in my future either way.

 

[Needafunboat]

stock prop height for a starliner

The balmy 44 degree MI weather inspired me to check my prop height on the starliner. The motor is mounted in the middle of the 5 mounting holes (no jackplate)

I get a prop height of about 5 to 6" below the bottom of the V- does that sound about right?

I'll probably run it like that for a while and see what it does. I can go up about 1.5" without a jackplate. Top speed isn't the #1 priority, but I'd like to go as fast as possible with good handling and holeshot. I have a few years of tuning ahead of me...

First we need to get those lakes thawed out...