Merc 260 water not flowing out of dumps

[Brookbbb]

On which boat??? LOL

ive run 260's promax cut like a 260 and 200's on one piece plates In the past. Same situation get gravel up in the passages and flow sucks out the dumps.

Haha fair enough! Even tho I have visable flow at the top of both heads with the t stats restrictor covers removed, you think I should still remove the heads and diverter plate?