My boat has the freshwater flush adapter installed on it. Is it safe to run the engine while its hooked up to this, or only when you have the muffs on the outdrive?

Safe

I don't use muffs at all anymore. Only use the flush adapter to flush the engine, while running.

Awesome. I was just flipping through my owners manual and service manual to try and figure out how to winterize this boat and its fresh water system (I like to be prepared way before it gets cold), compared to the Merc in my last boat, and it didn't say anything about running it on the freshwater flush with the engine on. The guy I bought the boat from did it once, but he didn't seem to be that mechanical.

Thats the way I do mine a lot of the time too, I use muffs sometimes also, no problem either way.

I think it is 2003 and newer model you can run the engine while flushing through the onboard fitting.

Older ones you have to use muffs. Has to do with the position of the impeller on the newer/older models.

If your boat doesn't have the flush system you can run the boat off it can actually be added. Found the info on marinepartsexpress.com at the bottom of the page.

Page 83 of the 2004 operator's manual: Volvo Penta engines incorporate an engine flushing port designed to flush the engine with fresh water while the engine is running.

Good system.

Not so for 2002's. Have to use muffs.

Mike

You can change it to make it work like the 03 and beyond if you want to.

http://www.marinepartsexpress.com/engine_flush.html

not sure, but i don't think the engine should be run above idle on muffs or a flush port. at least that's what i was told on our old boat.

On muffs I will run up to about 1200 RPMS with good water pressure.

Does this "engine flushing port" allow fresh water directly into the block, or does the engine have to be warm enough to allow the theromstat to open before getting to the block?

The flush does not go directly into the block.
I was told by the dealer to allow the temp to come up to operating, to allow the thermostat to open, then continue to flush for 5 mins or so.

That's what I do.

oh, BTW...

I also put a brass quick connect fitting on the flush port tube, with a shut-off valve. This is to avoid needing to deal with the plastic cap it comes with.