outboard correct transom height

[George.K]

Hi

I have a 1997 Bayliner 1702 LS with a 1997 Force by mercury 90 HP.The leg and gear is Mercury.

Since I want to remove antifouling and restore the gel coat, I remove the engine to have clear space.

After reading a lot of articles on internet, I get confused if my motor is installed in the proper height.

The transom on my boat is 20?? (508mm).

I wrote that the standard height for overall good performance is that the ant ventilation plate must be in the same level or little lower from the boat bottom.

My question is which one is the anti-ventilation plate in my motor? ( please see attached photo-it?s not my boat )

a) If it?s no:2 then is about 0.5 inch higher from the boat bottom.

b) If it?s no:1 then is about 2 inches lower from boat bottom.

By measure the shaft of me motor, from bracket to plate no:2 is the same like the boat transom 20?? (508mm).

Distance between plate 1 & plate 2 approximate 2.5 inches



I would appreciate any advice.

 

[carholme]

Re: outboard correct transom height

Outboard Motor Shaft Length

In your photo #1 is the anti ventilation plate and you should be measuring from the bottom of that as per the attached drawing. Should be at least even with the bottom of the boat up to about 1" above the bottom.

Gerry

 

[JB]

Re: outboard correct transom height

What carholme said as a starting point. From there raise the av plate (or lower it) about 1/4" at a time seeking optimum performance.

 

[jerryjerry05]

Re: outboard correct transom height

From the pic.That aint no 17 ft Bayliner.
That motors too big for that boat.
The link carholm posted is what you need to look at.For mounting.
The cavitation plate should be even with the bottom,max 1in below or above.
I'm sure any cop who looks at that transom and outboard might mention it's WRONG.
That boat should probably have a 50hp max.
That motor has enough torque to rip that transom out.
Make sure you wear your life jacket and only take out people you don't like or children you haven't gotten used to

 

[George.K]

Re: outboard correct transom height

Thank all.I will lift up the motor about 1/4" at a time and check the performance. The most importance is that i find out that my motor was installed by the previous owner in a wrong height.

 

[jerryjerry05]

Re: outboard correct transom height

Like I said that motors too big for that boat.
But to make sure it's right.
Take a hydrolic jack.
A straight piece of wood or metal.
Place the motor at 90d or straight up and down with the transom.
Then put the jack under the very bottom of the hull.
The piece of wood goes on the jack and it should stick out straight from the transom.
The cavitation plate should rest on the stick.
A little down or up won't hurt.

 

[George.K]

Re: outboard correct transom height

Like I said that motors too big for that boat.
But to make sure it's right.
Take a hydrolic jack.
A straight piece of wood or metal.
Place the motor at 90d or straight up and down with the transom.
Then put the jack under the very bottom of the hull.
The piece of wood goes on the jack and it should stick out straight from the transom.
The cavitation plate should rest on the stick.
A little down or up won't hurt.

the boat on the picture is not my boat, mine is a bayliner 1702. Thanks for your advice Jerryjerry05

 

[jerryjerry05]

Re: outboard correct transom height

Good I was imagining the boat hitting a wave and the motor twisting the transom and the whole thing becoming an anchor.