boat that will not plane out, continued - have info

[gregscharf]

I have a 15' boat with a Johnson 75 HP that has trouble planing out. Lubedude and walleyehed - thanks for replying, I have your information. Sorry it took so long to get back to you. The cavitation plate is about 2.5 inches from the bottom of the boat. The props I have are 10 1/8 x 11 and 10 x 9 1/4. The engine is rated at 4000 to 5000 rpm with 75 HP at 4500 rpm. I don't have a tach on the boat, so I don't know what the rpm is at WOT.

 

[poolecw]

Re: boat that will not plane out, continued - have info

Is the cavitation plate 2.5" above or below the bottom of the boat? If its 2.5" above the bottom, then it may be sitting too high on the transom.

 

[gregscharf]

Re: boat that will not plane out, continued - have info

The top of the cavitation plate is 2.5" below the bottom of the boat.

 

[poolecw]

Re: boat that will not plane out, continued - have info

Raise it up a hole or two and see what kind of results you are getting. <br /><br />You really need to get a tach. Their are small digital tachs available that are cheap and easy to install yourself, like this one: <br /><br /> http://www.tinytach.com/tinytach/index.php <br /><br />If you have a tilt lever on the motor make sure the pin is set correct.

 

[ob15]

Re: boat that will not plane out, continued - have info

I would raise the motor up unitl it is at least even with the bottom of the hull (keel if deep vee).

 

[gregscharf]

Re: boat that will not plane out, continued - have info

I appreciate the input. Being new to boats requires some new education. Thank you.

 

[R.Johnson]

Re: boat that will not plane out, continued - have info

This is a 1964 engine! You can't go to high on the transom because of water pick-up location. Also these prop's are not cupped. The engine should turn the size prop's he has. Sound's like the engine need's a good going over, Starting with a compression test, and a sync & link.

 

[walleyehed]

Re: boat that will not plane out, continued - have info

For the sake of possibly saving an engine, don't raise the engine until a tach is installed and a base-line is set with it mounted where it is first.

 

[gregscharf]

Re: boat that will not plane out, continued - have info

I am looking into getting a tach. The other day my father-in-law (the original owner) was listening to the engine run and he said it sounded a tad bit rough. I am going to take it back to him with a tach and check the timing, etc.