DIY static outboard bracket

[garagenc]

Here's my 2 cents worth:

Any Stainless angle over 3" x 3" x 3/8" for outside, Inside I would use a full plate 1/4" thk across the transom to disburse the force on the transom. The plate should be a minimum of 4" larger than the distance across and above the outside area of the angle frame dimension. Bolts 5/16" dia minimum 2" down/inside from each end and then spaces about every 8" apart. Grind the extreme ends of the angle where they lay against the transom. All welds should be full penetration for the bracket and ground smooth on the side against the boat. This will not allow any brunt force against the fiberglass.

Do not use aluminum, you would need to beef up the thickness from 5/16 to 1/2" thick to compensate for strength and it would need to be out of billet aluminum.

[spareparts]

remember also, you need lift, not necessarily set back, although set back requires less lift(rule of thumb is 2 inches set back covers one inch lift), I made a lift only bracket for a 70 by using two pieces of angle aluminum, I used the original mounting holes in the transom to mount the aluminum angle use flat head bolts so they fit flush), and drilled new holes thru the angle and transom for the engine mounting bolts. The top bolts were not supported by the transom, they only went thru the angle, the bottom bolts went thru the angle and hte transom

[peiserma]

Originally Posted by spareparts

remember also, you need lift, not necessarily set back, although set back requires less lift(rule of thumb is 2 inches set back covers one inch lift)

I'm confused by that statement. If the transom is angled down towards the water, wouldn't the setback due to the bracket require more lift, not less?

[phatdaddy]

water is "higher" the further back from the transom you go. the deepest hole your boat makes in the water is at the transom.

now your really confused

[peiserma]

Ah! Now I get it. I wasn't considering the most important part, and that is the boat moving forward on plane... Thanks for clearing that up. Of course that makes it a little tougher to deterimine how high the motor needs to go.

Maybe its better to just buy an adjustable bracket for that reason alone? If i don't get it right the first time, I need two more SS angles.

[phatdaddy]

this is a bracket i made for my whaler. it was built for a 15" motor and when i repowered, i wanted a 20" in case i put it on any other boat. granted this is a lot less weight & hp, but you get the idea. the original transom is about where the starboard stops.

[smokeonthewater]

no we're ALL confused.. lol..

YES the further back the engine gets the HIGHER it must be... not because of the angle of the transom (you are measuring height above the keel not angle) The reason the engine gets higher further back is because the boat displaces water even on plane... the water right at the transom is lower than the water in front of and behind the boat... as soon as the transom leaves a given point in the water it immediately starts to rise towards it's original level so behind the boat is uphill....

ALSO the keel will be pointing uphill toward the front so straight back (no matter the transom angle which you build around) is downhill....

sooo your engine moving downhill where the water is moving uphill requires more lift....


You do not need any huge washers or plates on the transom... the angle iron will already be spreading forces much better than the outboard brackets... you only need the same washers you would need to mount the engine directly to the transom..... under power the only forward force on the transom is at the very bottom end of the bracket or angle... the top is pulling away from the transom.....


ALSO nobody mentioned this but the bracket will not increase leverage on the transom... in fact it will lower it... the forces are at 3 points... prop shaft, bottom of bracket, and top bolts through transom..... a simple lever with the bottom of the bracket being the fulcrum

the prop is the fat kid on the teeter totter and the transom top is the skinny kid..... the bottom of the bracket is the hinge and the top bolt is you.... by moving the prop up you have moved the fat kid closer to the hinge and made it easier for the skinny kid to lift him



You don't HAVE to get it right the first time... your motor has the adjustability built in... just get your bracket close but not too high and adjust the engine up as needed for max performance

[garbubba]

I think you are going to have trouble if you mix metals unless you can insulate that aluminum plate from the stainless angle, the plate will act like a sacrificial anode to the bracket, especially in saltwater.

[smokeonthewater]

he has no need for an aluminum plate.... all he needs is angle and bolts

[phatdaddy]

i think he was going to put some plate on the inside of the transom for backing plate