14' aluminum Run-About Transom Height

[JJBoatr]

Mornin all,

Working on a 67' Creatliner Commodore Speedster with an Evinrude 25352A 25hp long shaft outboard.

My question is; what height should my transom be? When I first got the boat I didn't have a long shaft kit on my motor so I cut the transom down to 15". I have since acquired a long shaft motor and brought the transom back up to flat across the stern of the boat as it was before I cut it and it measured 21". This height put my water pick up dead even with and perhaps slightly above the keel and for fear of not getting water to the pick up I cut it back down to 19.5". Water pick up problem solved but now I get a rooster tail off the seem of the long shaft extension housing unless I trim all the way up to the 4th pin position. I also still catch an air bubble when turning at speed or when cruising over a 6" chop. Should I run the transom at its original 21" height? That would solve the rooster tail issue but I don't want to lose water pick up. Will the swell between the boat and motor come up enough to pick up water at that height? Thanks for the help.

 

[ondarvr]

I think we're going to need pics.

 

[JJBoatr]

I just tried, said my file size was too big. I'm trying different camera settings.

 

[JJBoatr]

No Title

 

[JJBoatr]

I forgot to mention that I placed a 1/2" shim between the motor and the top of the transom to stop the rooster tail. So the motor is actually up at 20" from the bottom of the boat. the ruler in the photos above is being held flat on its edge on the bottom of my boat. The more I look at this the more I think it will be fine at 21" at the transom. Just never heard of anything other than a 20" transom for long shaft motors.

 

[ondarvr]

On flat bottom boats sometimes the prop needs to be a bit deeper (yours looks like a shallow V or flat), plus if there are strakes on the hull they can interfere with water flow when you turn, so sometimes the set up isn't ideal. Yours looks deep enough (maybe too deep), but if it ventilates when turning there's not much you can do.

 

[ondarvr]

I forgot to mention that I placed a 1/2" shim between the motor and the top of the transom to stop the rooster tail. So the motor is actually up at 20" from the bottom of the boat. the ruler in the photos above is being held flat on its edge on the bottom of my boat. The more I look at this the more I think it will be fine at 21" at the transom. Just never heard of anything other than a 20" transom for long shaft motors.

​Motors and transoms are rarely right at the 15" or 20" height, they tend to vary a bit by brand, so you just do what you need to do to get it right.

 

[JJBoatr]

Thanks for the response. My boat is a shallow V and not quite flat at the transom. I also have a chine on each side of the keel rib. For my own education; is it ok to have the water pickup even with the bottom off the boat? That's where it will be if I make the transom height straight across the back like it was originally.

And I completely agree, I think I've got it too deep right now. As evident by the stupid yet entertaining rooster tail that's produced at any trim setting below the highest.