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What is the optimum depth of a motor(prop)?The boat and motor are nothing special,but she floats,and we catch fish in her.This is why I ask.

FYI it's a 14ft SmokerCraft Fisherman (1987)Evinrude Tracker 40HP(1990)ALL STOCK

I bought the setup three years ago.This year I installed a CMC aftermarket power tilt/trim.The best thing I have ever done.I think the assist was shot because it was a monster to pull up.Anyway the CRC works fine.When I installed it,I read that by raising the motor would increase performance.I did raise it a little but there is room for more.The CRC really helped with getting it to plane,before I was stuck with the only setting,down.I do get more splash or whatever you call it with the CRC.Not a rooster tail,it's right behind the transom.It only does this all the way down,like it was before.I'm not sure if it is from the CRC or the fact that now the motor is about 10" back off the transom.I can live with it the way it is and like I said it has increased performance.Just wondering if I moved it up higher(we are talking inches)would it be even better.

So what is the best spacing between keel and prop for this set up.

What say you.


BTW  I'm new here and love this site.

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I think I'm at 2-3/8" below pad on my Triton. Tritons like a lot of lift but not all boats will be the same.

Keep in mind raising the motor can make the boat turn more RPM and if it's to high you will loose water pressure and burn the motor up.

I'm assuming you don't have a water pressure gauge or a tach?

How far below pad are you at now?

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First, let me say welcome to the site.

As for your question on proper motor height, there is no magic number, too many variables involved for that. The type prop, the amount of setback, the type hull, weight of the boat, location of water inlets on lower unit, etc all have an affect on motor height.

One thing, you have to be very careful about raising the motor if you don't have a water pressure gauge installed in the boat. If you get it up too high, it will start sucking air in the water inlets and can fry the motor. If you look, you will see the top holes of the water inlets on that motor are not very far below the anticav plate.

Then you have the prop. High rake, deep cupped props can be surfaced, meaning they can run where they are actually coming out of the water. Where you standard low rake, non cupped or minimum cupped props have to be run well below the surface or they will cavitate. High rake prop give a lot more bow lift than standard props and some hulls don't like that, they prefer a straight push.

The more setback and the more rake plays a huge role in setting motor height, and the type hull the you have.

With all that said, without a water pressure gauge, I would not raise the motor any higher than having the anticav plate about an inch above the bottom of the boat. This is checked with the bottom of the hull and the motor trimmed so the anticav plate is level.

For any small difference you might see in performance is not worth burning a motor up trying to tweak it right to the max. To start with, you would need to try a few different style props (all of them stainless) to see which on works best on your hull, then you play with engine height. I have one prop I can run 1 1/2" below the pad, another I have to run 4 1/2" to get bow lift, but that's on a much faster boat with a much bigger motor than you are dealing with.

When you hear the term "below the pad" it's is how far the center of the prop shaft is below the very bottom of the boat, yours does not actually have a pad. The pad is the very bottom section of the hull on riser hull. I don't think yours has a riser hull. The is measured by leveling the bottom of the hull and motor and measuring it. Notice now, I mentioned setting you anticav plate an inch above the hull, that was not setting the prop shaft a certain distance below it.

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Thanks for he replies.I should leave well enough alone.She runs as well as expected,no reason to squeeze the lemon.

Good luck.

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