BIA bolt hole distance from top of transom.

dkhntr04

Recruit
Joined
Jun 16, 2009
Messages
5
I'm mounting my 1973 Merc 500 with a universal tilt/trim unit from TH-Marine. The unit is very similar to the CMC PT-130. The tilt/trim unit has the standard BIA bolt pattern.

The boat the tilt/trim is going on is a 1999 Alumacraft 16LTD Mag that and the transom has never been drilled. I've got the bolt pattern down fine but I am wondering what the standard distance from the top of the transom to the centers of the first row of bolt holes (the ones 12 7/8" on center). I would like the holes to line up with new/newer 40-50hp outboards in case I or a future owner plan to upgrade later on.

I can hardly find any info online about this. On site states 1 7/8" from the top to the center. I will be stopping by a dealer tomorrow to ask but the more input the better. Thanks!
 

ddrieck

Senior Chief Petty Officer
Joined
Jul 12, 2007
Messages
655
Re: BIA bolt hole distance from top of transom.

That top measurement will depend on a number of things

- Transom design
- Outboard leg length
- position of the cavitation plate in relation to the bottom of the boat

layyour measurements out so that your cavitation plate is about 1/2'' - 1'' above the very bottom of the transom. Don't worry to much about the top measurement being in place for a future upgrade as nearly all outboards have adjustability to them.
 
Top