out baord height

[Dreamland]

2002 Polar 1910 center console with 140 hp Suzuki 4 stroke

just had boat serviced and now

asked mechanic to raise motor 1 notch, he insisted it be lowered 4 notches - now on calm water with tilt down it sprays a 12 foot fish tail and full throttle rpms' are up 500 with tilt up the boat bounces like crazy

cap plate even with keel or 1 inch above??

 

[Scott Danforth]

anti-cav plate should be about even with the keel, unless you have a jack plate, then with the extra stand-off, you start raising.

 

[99yam40]

I am trying to understand how lowering the motor 4 holes could raise WOT RPM.
that would be opposite from everything I have read

 

[ClassicAQ]

I am trying to understand how lowering the motor 4 holes could raise WOT RPM. that would be opposite from everything I have read

I am trying to understand how lowering the motor 4 holes as well as motor being trimmed all the way down could spray a 12 foot fish tail.

 

[boscoe99]

Most motors are mounted lower than is optimum. Start with the anti-ventilation plate about an inch above the keel level. Raise the motor one bolt hole and test it. Raise it another bolt hole and test it. Repeat the process until something adverse happens. More than likely the propeller will ventilate excessively with up trim. Drop the motor back down one bolt hole.

Every boat, motor, owner is different. Trial and error is needed for a specific application.

When running at cruise RPM and the motor trimmed up only to the point of best efficiency (and no further) the anti-ventilation plate should be skimming the surface of the water.

 

[jimmbo]

Optimum height varies and is dependent on choice of props, speed of boat, intended use age of boat, and driver tolerance

 

[Sea Rider]

For recreational, family leisure boating dial OB/transom height for water flow at speed to skim right under small upper plate, just where the sharp edge that cuts water starts. AV plate must ride parallel to water level once combo is on plane. If flow skims right over AV plate OB will achieve prop aeration on tight close turns and choppy water cond as ideal water bed height for best prop thrust will be dramatically diminished.

You must check that suggested height on calm flat water cond while visually watching what's going on at back transom to know if in need to raise or lower OB a bit till that cond is fully met. I'ts a much faster method to dial that wild guessing, raising OB till prop aerates or lowering till having splashing issues out or over transom.

Happy Boating