It looks like the blog masonry template pulls from the content field and not the excerpt field, so the only way to control the length of the excerpt it shows is with a more tag.
Is there any way to make it pull from the excerpt field rather than have to use more tags?
I didn’t see a setting for this and I poked around the template files a bit. So if I missed something obvious, I apologize.
When the theme is updated, this change might be lost. Just an FYI. I believe you can create a custom file, and make the changes there. This way, when you update the theme, your alternations will remain.