when you back flush. This going to sound bad. BUT fill the hoses up with water and then suck and blow in little jerky motions and the water could dilodge some peices. i have had to do that before, and 3 empellar vynes came out. that did not with just the water.

Had the impellar and housing replaced. Heating issue got better, but not there yet. 4000 RPMs boat runs about 170 degrees (according to the gauge). 5000 RPMs engine gradually heats up to 190 and hard alarm encountered. Seems like the more trim I add at the higher speed the hotter it gets.

Still encountering two beaps every minute. I've replaced a few sensors and plan to replace a few more.

Saltwater boat? Might have a restriction in the transom assembly from corrosion.

was a saltwater boat before I purchased....now freshwater.

Do you have any alarms going off?
Do you have a water pressure gauge?
Do you have even water flow out of each exhaust pipe?
If you have a sea strainer, it would look like a cross between a washing machine and a coffee can, somewhere low in the bilge. It more than likely has as a clear lid so you can see if the basket is full of garbage and would need cleaned out. If you have strong water pressure you more than likely do not have an issue here. An example of a sea strainer is below.





I bet this is it though...
Is the antifreeze bright peach/pink colored or is it getting dark and metallic colored? If the latter, its old antifreeze and its silting up in the closed part of the cooling system. Max life of AF is about 6 or 7 seasons. Its been discussed here on OSO in the past and some info should come up with the search tool.



[ATTACH=CONFIG]502057[/ATTACH]

A scan tool would be helpful here. You can measure seawater pump pressure at any RPM as well as port and starboard manifold temperature with one.

Also you can use a cheap infared thermometer to check each manifold and riser temp. That would help isolate the problem to the fresh or seawater side

Regardless of the main problem I agree that an antifreeze change is warranted if it's never been done on a 2004 engine. Finding and getting to the block drains can be a challange however.

www.rinda.com

Probably the best money one can spend on any boat with a SmartCraft engine.

Have you pulled the end caps off the heat exchanger and cleaned out all the little tubes in there?

Thanks for all the replies. I have the heat exchanger off now and will inspect later this evening. Checked the old TSTAT and seemed to be working. I have a new (160) ready to go in. Agree on the Rinda scan tool (visited thier web site) and priced the IR Thermometer on Amazon

You can pick up an IR thermometer also known as a laser pyrometer; at Lowes and Home Depot, and the like.