View Full Version : Transom Height

08-07-2014, 07:41 PM
I'm at the point where I'm starting to plan out my transom for my cruiser restore. I did some searching, but didn't really find the answer I'm looking for. I will have a 20" 100-150hp outboard. The rake of the transom is 12*. I'm thinking somewhere between 19-20" so when it's trimmed on plane, the anti vent plate would be close to flush. Open to other suggestions and advice!


08-08-2014, 01:33 AM
If you are restoring, build it the way it was. If you are modifying a boat from an I/O or inboard to an Outboard, some serious structural considerations need to be made.

As for overall mounting height, consult the manufacturer of your outboard of choice and accommodate that appropriately. Keep in mind the your transom may rise above your mounting point at the sides.

wizbang 13
08-08-2014, 05:35 AM
"trimmed at plane", what does that mean? My own boat planes between 12 mph up to 40 mph. All speeds are trimmed differently.The speed is adjusted more with the trim than with the throttle .
Anyway, You want the anti vent plate aprox. flush with the bottom of the boat . A bit higher for high speed performance , a bit lower for low speed performance.
(if your boat winds up needing a "dolfin" or one of those bolt on plates, something else is wrong).
Transom angle is meaningless once the boat is out of the hole and planing.

08-08-2014, 07:02 AM
Maybe I was over thinking this part of the build. The "trimmed on plane" was referring to the motor being at a higher angle, making it "shorter" to the transom, so if it was flush when it's down on the trailer, it may not be 1/2" short when trimmed up. It will be a boat that only cruises at 30 mph, won't be a speed demon.thanks for the insight so far


08-08-2014, 07:05 AM
Mount engine so that the plate is even with the bottom ( +/- about 1/4") when the engine is trimmed all the way in.


Tom Wilkinson
08-08-2014, 07:15 AM
Mine is about 1/4" above flush when trimmed all the way down. That seems about right. I could come up a little for better speed performance but its not worth it. Trim makes all the difference in performance. I'd never have a boat without power trim again.