outboard motor mounting height?

[wyelkhunter73]

Question about outboard motor mounting height. I got a 2003 180 combo this spring and had a newly rebuilt Merc 200 hp EFI put on it. The motor was mounted to where the bottom of the cavitation plate on the motor is 1.25" above the bottom of the boat. When I trim the motor at cruising speed or faster it seems the bow of the boat barely comes up speed and RPM does not change. The prop never cavitates either even at full trim. Is this normal for this type of boat? I am only getting 5000 rpm WOT, I know that is low but I want to make sure motor is set right before I go about changing props. My previous boat was an 18 foot aluminum and when trimming the motor I could really tell a difference in speed and RPM.

 

[airshot]

I was alway taught the cav plate was to be right at the bottom of the boat.

 

[Chris1956]

Have someone drive the boat on plane and lean over the transom and see where the antiventilation plate is riding.

If the plate is higher, the effect of the trim is lesser, but speed may be higher. "driveability" may also be decreased.

Lower mounting may give more effect to the trim, but lower speed. It may be easier to drive, however, So you get to choose what you want.

 

[wyelkhunter73]

Have someone drive the boat on plane and lean over the transom and see where the antiventilation plate is riding.

If the plate is higher, the effect of the trim is lesser, but speed may be higher. "driveability" may also be decreased.

Lower mounting may give more effect to the trim, but lower speed. It may be easier to drive, however, So you get to choose what you want.

Thanks. The antiventilation plate is about 1.75" below the water when running on plane, 4200 rpm cruising speed

 

[Chris1956]

OK, if the A-V plate is 1.75" below the water when on plane, that is causing a lot of drag. Raise the motor 1.75" and see what happens.

 

[jimmbo]

What prop are you running? That can make a big difference as to how high you can mount the engine and far out you can trim

Right from Mercury

 

[wyelkhunter73]

What prop are you running? That can make a big difference as to how high you can mount the engine and far out you can trim

Right from Mercury
View attachment 366476

Laser 2 21 pitch

 

[QBhoy]

Thanks. The antiventilation plate is about 1.75" below the water when running on plane, 4200 rpm cruising speed

You need to raise the engine. The AV plate should be at least an inch higher than the hull and probably higher even, on a set up like that.