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captlloyd · 13-06-2019, 11:31

A poor design, pivot point and support bracket are positioned to close together to have and real strength. You will never be able to tighten the bolts enough to have any real strength. You need to get some Distance somehow between those two points.

capt jgw · 13-06-2019, 12:02

I custom built a bracket similar to this. Not at the boat now and I don't have a photo, but I'll try to describe it. Instead of the
curved arm coming off the pivot, I put an arm about 2" wide going straight down ending about level with the bottom of the alternator. The curved arm goes from there to the bottom bolt on the alternator. That holds the tension just fine and the belt does not slip. I first made it just like the Universal bracket but as the OP says it wouldn't hold tension. The rest of the bracket is just like the one shown here. I couldn't use the Universal bracket because my manifold is a different style and the dimensions are not the same. You should be able to modify the Universal bracket like this.
As Roland mentioned above I ended up using a turnbuckle instead of the arm. Holds tension better, doesn't require you to overtighten the bolts and is real quick to adjust. Didn't use a marine turnbuckle, just an aluminum and stainless one from Lowe's. Cost about $4.00

mikeo16 · 13-06-2019, 12:19

I just completed mine also. You need to read this article which highlights the issues with the supplied bolts https://www.google.com/url?sa=t&sour...6iofO9-p5MrJqA
Go to any auto supply store like Napa, Autozone, or CAP and get the proper, longer, grade 8 , 5/16" cap screws. I have had no issuers

singlespeed · 13-06-2019, 13:30

Ditch the flat washer and the split lock washer. The flat washer you are using will slip on the bracket surface. Using the split lock washer alone will not do the trick. Purchase a serrated lock washer and install, torque per spec.

Chuck Hawley · 14-06-2019, 08:39

I know the following will be looked upon as a kludgy solution, but it worked for me on a Yanmar/Hitachi installation.

I bought a second bolt, washer, and lock nut and placed them immediately adjacent to the adjustment bolt so they provided a sort of "stop" on the bracket. I could remove the adjustment bolt on the alternator and it would not move. This just added more friction (and more complexity) but the solution cost about $1.20 for the parts. You could, presumably, use any grade of bolt and any pitch of thread since it just screws into the nut on the other side.

Chuck