Cavitation Plate Height on a notched or step transom

[pjbass]

I have 1996 Stratos 280 SF with a 1997 Johnson Fastrike 175hp that I added recently. I'm trying to get the best performance out of the engine and boat. The engine is running with a 14.3 x 21 prop (3 blade aluminum) and I am having a problem reaching 5000 rpms. The only time I have hit 5000 rpms is when my trim gauge needle reads 3/4 up at a speed of 49 mph(gps). The boat has, what I call, is a "step" transom and the engine is mounted as low it can go with 1-inch over the keel of the boat.

My questions are, should the boat perform a lot faster? If I raised the engine, will it increase the RPMs and performance?

Can someone provide me with some insight?

Thank you.

 

[pjbass]

Re: Cavitation Plate Height on a notched or step transom

Can anyone help? I'm still not hitting top speed. 50 mph @ 5000 rpm WOT.

 

[foodfisher]

Re: Cavitation Plate Height on a notched or step transom

Prop pitch will affect rpms. Try prop forum for explicit answers.

 

[Bob_VT]

Re: Cavitation Plate Height on a notched or step transom

Sounds like your motor is mounted too low,

 

[pjbass]

Re: Cavitation Plate Height on a notched or step transom

If I change the pitch, will it help the speed?

 

[alwims]

Re: Cavitation Plate Height on a notched or step transom

On my Ranger, with the "step hull", the recommendation for a starting place, is the 'PROP SHAFT' 3 1/2" below the bottom step of the boat. I would imagine your boat would be similar.

 

[pjbass]

Re: Cavitation Plate Height on a notched or step transom

Does the ranger one step or two steps? My Stratos has two steps. The first step has the aeratos screens follow by the next step and finally the transom. I sent an email over to the manufacture and they stated the following, "It should be 3.5 - 4.5 inches prop shaft to pad." So, tell me, which is the bottom step of the boat or pad?

 

[alwims]

Re: Cavitation Plate Height on a notched or step transom

The very last step is the pad bottom. The Ranger has 3 steps. Remember, on a Bass Boat, you are mounting per the prop shaft and NOT the cavitation plate. Just forget about where the cavitation plate ends up. Mount per the prop shaft and the cavitation plate will be where it should be.

 

[ddrieck]

Re: Cavitation Plate Height on a notched or step transom

The flat area on the very bottom of the hull/transom is the "pad" and when running at max performance and the right trim the only portion of the hull in the water is the pad.

The easiest way to gain performance and speed out of a padded boat is to install either a manual or hydraulic jack plate. If you like playing around with or have need for vertical up and down movement for varying conditions install a hydraulic jack plate. You could install a manual jack plate; start low (at the manufactures recommended prop height) and move up in short increments until you start to get cavitation, lower back down 1/2'' - 1'' and you have found the sweet spot that offers the best performance. Just be careful not to go up so far that you starve the outboard of water. I recommend a water pressure gauge with the installation of any jack plate.

Good deals on both manual and hydraulic transom jack plates here:http://transom-jacks.com

 

[pjbass]

Re: Cavitation Plate Height on a notched or step transom



I think I got you guys. So, correct me if I'm wrong but the bottom step is the aerators step? I know that the keel is below the drain plug. See attached photo.