DIY static outboard bracket

[spareparts]

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 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

sorry, I did word that screwed up, Smoke explained it better than I did, you get the idea. The further you go back, the higher you can run the engine

[RidgeRunner]

What fasteners do you use to keep from having dissimilar metals?

[Destroyer]

Originally Posted by RidgeRunner

What fasteners do you use to keep from having dissimilar metals?

Unfortunately, that's one of the conundrums of boat building. The bolts of choice are Stainless Steel because of their strength and corrosion resistance. But, they are dissimilar to the Aluminum that the outboard engine is made of. That's where the use of sacrificial zincs comes in. Just remember that the less dissimilar metal there is, the less potential there is for galvanic corrosion.

[peiserma]

Thanks a bunch, you've given me enough to go on for now. I really appreciate it. I'll see what 1/2" angle costs locally, take some measurements of transom and motor, then sketch up some plans. I will post the sketch for final input and recommendations for the proper height. Will need until next week.

Last question before I hide in the mad scientist cave to sketch up my plans: if i use 3" x 3" angle 1/2" thick, setback will be around 4". Using the 2" setback = 1" of lift rule, that equals 2". So I should plan to raise the motor 3" (recall it is a 20" transom and a 25" motor) in relation to my old one?

[smokeonthewater]

the math here would net you 7" BUT instead of just assuming you need to measure from the keel to the top of the transom and from the anti vent plate on the motor to the bottom of the transom hooks.......
Understand that you will set only your lowest possible height here so build to put the anti vent plate 1" below the expected desired height... in this case since you expect to need it 2" above the keel you would aim for a minimum of 1" above the keel.... Then you can raise the motor one hole at a time till you get the best performance.


example: if your motor shaft is actually 26" and your transom is actually 19 then you would need 9" -1" for a total of 8"

[smokeonthewater]

Honestly I have to admit..... while I can't suggest it to anyone else as it is officially a BAD idea I would probably just run the 150 hp pre made plate.... Jus sayin

[Destroyer]

Originally Posted by smokeonthewater

Honestly I have to admit..... while I can't suggest it to anyone else as it is officially a BAD idea I would probably just run the 150 hp pre made plate.... Jus sayin

X2.... Since most manufacturers build in a certain load above the rated safe load, and if money wasn't all that important, I'd tend to do the same thing. Understand this is NOT a recommendation, just sayin what I would probably do.
Much like me running a 18hp Kicker on an EZ-IN kicker bracket for several years even thought the bracket was only rated for 10hp. But then again, I've never considered myself as the brightest candle in the box... so what the heck do I know....

[peiserma]

Originally Posted by smokeonthewater

Honestly I have to admit..... while I can't suggest it to anyone else as it is officially a BAD idea I would probably just run the 150 hp pre made plate.... Jus sayin

I understand the sentiment, but I am an (electronics) engineer working in the nuclear power industry. My design comfort level starts in the 30% to 50% margin range, and if I can talk people into a more robust solution, I will. Then I add a backup system. Actually, we like four backup systems for anything really critical.

It may work just fine for a long time. I understand perfectly well that T&H designed in margin, but I could never sleep well at night using something beyond rated capacity. Fukushima got hit by almost 10x worse than it was designed for, which has no bearing on this topic, but it does reinforce the idea that safety can never have enough margin.

While I appreciate the viewpoint, I'd never be comfortable with it