Water Pressure fluctuating, exhaust tone change
 

The water pressure was low, 25 or so max. at wide open Under steady cruise exhaust tone changes intermitently, suspect exhaust is loosing it's water. New impeller start of season, checked it still good. New cric. pump as well. Pulled the line for the sender off the block and gauge, blew it out with a compressor, and alot of sand came out of it. The gauge moves back and forth between 20-30 lbs. at around 3k, steady cruise, no sea or trim changes. Can't make it do it or not do it. Still have the very noticable exhaust tone change. Any ideas what could be effecting the flow? Also, the coolers are all clear. Thanks

if you have sand in the line . . . you might have sand in your block as well still

20-30 at 3000?

Hate to hear what it is at WOT.

I installed relief valves to have my WP 25 psi at WOT. Much higher and the hoses started to swell up from the high pressure.

Will do on back flushing it. Boat has always run 35 psi WOT. This is what Reggie report said it should have.??

What outdrive? Low water pickup, dual pickup or standard with maybe a couple of the top holes plugged? Low water pickups tended to run higher to "too high" pressure. Pressure will fluctuate "some" just due to water chop, turbulence (for lack of a better word), etc. Exhaust tone will change some if you are "just barely" on plane because the back of the boat is still sitting low enough in the water and the thru hulls are not completely out of the water all of the time ... maybe that?

35psi at WOT is ok. My 47 does that.

Bravo one drive, standard pick up I guess? Not sure how to tell. Boat does it on plane. Backflushed system, nothing but water came out. What would be the best way to make sure top holes arnt plugged, they dont appear to be by eye. Also a little more info, out the other day and pressure drops if running at WOT for 1 min+ or so, to like 10-12lbs, not over trimed or anything. Used to read 35+ in same conditions.

Could be air leak on suction side of the pump .... check your hose clamps to be sure they are tight. Do you have a Fountain fresh water flush system .... check to see that valves are set correctly and that the gate valve to the outdrive is open and ball valve to garden hose is closed. Is your sea pump metal body or plastic body? If I remember correctly, the metal body pumps had a rubber plug in the aft end of the impeller.

Plastic pump. I will re check hose clamps. I dont think i have a fresh water flush system. There is just a hose from the outdrive to the raw water pump.