TOPIC: Transom Height- questions?

I have rebuilt my Fabuglas Transom to it's original height- as indicated by the untouched outer skin. It is 21" from the top to bottom. I'm a bit worried that this might make the cavitation plate too high for the Merc. The water inlets will still be far below the bottom of the boat.
However- Measuring the Hydro-Sports transom has me confused. It is a "stepped" transom. This transom is only 17 1/2" tall. Then there is a step where the hull turns toward the front for 7" , then it turns down an additional 5 1/4". This makes the overall transom 22 3/4" tall. The cav plate is about in the middle of the lower "step"- and the water inlets are about 50/50 above and below the bottom of the boat. I would think this thing would starve for water at high-speeds, but apparently it doesn't.

Should I trim my transom-height 1/2" or so to be safe?

I think your good to go. I rebuilt a transom last year and made it 22.5" for a long shaft evinrude 50hp. Your new bass boat's transom is like a set back. The farther back the motor is set the higher the motor needs to be. If I were to build up a new transom it would be higher then 21" but not much more, Mike

ps... this is only my opinion...see what others think...

Ray, while I'm no expert, I have been gathering research info on this subject and paying close attention to input from as many experienced folks as possible. I believe Mike is right, I wouldn't shorten your transom at all. The anti-ventilation plate needs to be (up to 1") above the line of the hull for best economy and performance. My boat is currently set dead even, and the water passing under raises quickly once the hull is clear so it's hitting the gearcase above the plate, causing splash and more importantly increased drag.

You can reassure yourself by measuring your motor from where the bracket rests on the transom down to the vent plate. If it's 20", you're good to go IMHO.

I'm with the others on this one. 21 inches will work perfect for ya.

classicfins wrote:

I'm with the others on this one. 21 inches will work perfect for ya.

I sorta figured it would be OK.. That's the height it was for the long-shaft (20") Johnson 90hp.
To be honest, when I rebuilt the transom- I didn't even consider the height. I just made a template of the old transom.
I was just worried that some here suggested that the cav-plate could be "up to" 1" above the bottom. I still have to install the transom-cap... but that's only an 1/8th inch or so.


Thanks all!!!!

Also, keep in mind that the transom height is actually measured vertically, not at the angle of the transom. So, you would measure straight down to the plane of the boat bottom. Lay a straight edge along the bottom of the boat if needed. With that in mind, your transom would measure closer to 20-inches, not 21... Once you get your motor set up you may actually find you can go up with it a bit. Even with a non-performance hull you can gain better speed and efficiency with proper set-up...