BF225a4 - Flush Port Problems - What is this Allen Bolt?

I've got a BF225a4 and the flush port doesn't work. I've flushed from every direction--through thermostats through the pisser port, etc. to try to remove the blockage. Water flows everywhere except the flush port. It all looks clean inside the engine looking into the hole for the thermostat. And the engine runs fine and has plenty of water pressure. The tubes from the flush port to the engine are all clear. The problem is in the engine somewhere--presumably there is a blockage.

I want to remove the allen bolt in the photo below to see if it will allow me better access to potentially clear the blockage in the engine. Does this bolt have anything to do with the flush port? It is immediately next to where the flush port hose connects to the engine.

I looked in the Helm shop manual and doesn't say anything about that bolt. See the attached: View attachment Flush Valve.pdf

Note in the diagram - right upper side. There is nothing about it.

I suspect that it is some sort of access bolt, but not entirely sure. Try to take it out and have a look. You may want to treat it with some PB Blaster and tap it a lot before trying to remove.

I had a blockage in my flush port from grounding on a mud flat, I ran the motor on muffs while running water in the flush port and the mud finally broke free.

Thanks, all. I'll try both next weekend when I'm back at the boat. I'll take a look behind the allen bolt to see if it will let me clear anything, then run it in a trash can while also running water through the flush port.

Just wanted to close this out since I resolved the issue. As chawk noted, this bolt was an access bolt that provides really easy access to the line into the block from the flush hose fitting. There is a another one on the other side for the tell-tale that does the same thing.

When I pulled it out, there was a smooth, shiny surface. I thought it was metal because it was smooth and shiny, but thought it was totally bizarre that they would have a bolt that did absolutely nothing there. I scratched at it with a pick, and after some aggressive jamming and scratching with a pick, grains of sand/salt flaked off. It was just extremely packed in sand and salt. I took a small drill bit and carefully drilled into the packed sand since I was making no progress with a pick since it was packed so hard. Then I picked at it to clean it out, hitting it with compressed air periodically.

This was after I drilled through the sand.



This was after cleaning it out with a pick.



This little tube is about 3-4 inches. I went ahead and pulled the same allen bolt off the tell-tale and cleaned it up too. It wasn't obstructed, but there was some build up.

So if the flush port or tell-tale is blocked, and you've cleaned out all the hoses up to this fitting, this allen bolt gives easy access to clear up obstructions.

Good info and photos. Thank you!

Ditto. Well done. I, and I am sure others, appreciate the detailed pictures and narrative.