water pressure problem
 

so the problem is the boat will have 20lbs of pressure for the first 1/2 mile the boat is on plane , then the pressure drops slowly from 20 to 0 lbs in then next 600ft . then the temp goes from 140 to 195 and sounds the alarm ,after you go back to idle the temp will slowly go back to 140


we have no leaks
replaced the impeller
cleaned the strainer
replaced the thermostat
checked the block water pump
checked the oil cooler for blockage
checked the impeller housing for cracks
no water in oil
no visable hose kinks or blisters



the sea pump is moving water because the water is swirling in the strainer and spitting out the exhaust

IDEAS ?

Check for belt slippige so
Something could've getting warmed up and seizing or. Belt heats up loosens up enough to start slipping. Especially a v belt setup , check width on v belt if equipped ?

Do you have a fresh water flush system? If so, does it have a ball valve or check-ball in that system at all? There could be debris impeding flow at that valve if so; as I have seen that happen on more than a few boats.

Did you replace impeller and housing at the same time or just impeller? Replacing in a pair yields much better results, use Merc brand also.

I had the same issue.

After chasing my tail for hours, a friend looked at the housing.

Changed it and this were right again.

Ken

serpentine belt , will check

thanks for the idea

no check valve in mine .

thanks for idea

used merc brand impeller , will replace housing . just surprised because it does have pressure then looses it

I will replace the housing this week

Replaced the housing and another new impeller . Changed another thermostat , changed the inlet hose to the sea strainer and sea pump . Changed seals in the impeller shaft also . Tightness checked on the belt also

Is this a Bravo boat?

Yes , BUT using low water pickups

You may want to try replacing the water hose in the transom assemblies. They could be getting sucked shut. There is also a possibility (if this is a stepped boat) that the hull could be leaving to much air in the water and you are pumping air through the cooling system rather than water. If this is the case you will have to add thru hulls about 4" behind the rear step. There is clean water there. I would start with the water hose though.

You have a bad hose somewhere, as as flow, increases it closes off internally, reduce flow and pressure and it opens back up.

Like when you get a flapper from a bad fitting installation...or the hose could be delaminating on the suction side of the pump.

I've found wood chips in hoses that float around and then finally clog the first cooler enough to restrict water flow. Come to a stop and they must have floated back away from the cooler. I'm not sure that is exactly what happened, but it seemed to resolve my issue at the time.

Did you flush each hose out or just check the coolers?

fixed the problem , long story that would not help this thread caused the problem . thanks for all the ideas to check

I read this and thought the purpose of this site is to help others solve problems. You left us all hanging out in the wind. How does that help those who participated trying to help you?

crack me up . **** off guys I fiqured it out lol congrats glad youre on the water ...

Lol! I thought it... You said it. Oh well.

I guess your right , SORRY .

here is the story ....

took boat to tunner to get the engines re-tuned because of changing the 500efi intakes and having them ported . ran great and had 10-14lbs of water pressure . next week hauled the boat to the ticfaw 200 put the boat in the water and ran 1 mile up the river and this having no water pressure showed up , after going back to the dock I pulled the impellers and they looked great , replaced the one on the motor that was getting hot . now when I am saying hot I am saying 195 and setting off the alarm, when its idiling it will cool back down to 140 . so we looked at the strainer and exhaust and had water swirling in them . so we tried it again same thing 195 when running so we shut it down again . so after about 6 miles of checking I noticed water getting on the outside of my headers and looked down beside the port motor and saw a little of water running out between the head and block ... HEADGASKET blown . SO we took the boat home pulled the motor and replaced the head gasket and head because of missing metal between the chamber and water passage . OK NOW HERE IS WHERE IT GETS CRAZY . while the engine was out I put low water pickups on the boat , to help the water pressure . reinstalled the engine and took it to the lake . starboard motor has 20lbs now and port has 20 that will go down to 0 when the boat is on plane . so that's where I was stumped on this and started THIS thread .

now the problem was the water pickups I installed are too short when the boat is on plane for the port motor , and after I changed it back to the drive pick up its ok . during this I noticed the starboard motor is also loosing water pressure when its trimmed out .

so you see how I didn't think the pick up was the problem, because of the water pressure problem before the head gasket . this was a case of problem before was different that looked the same as problem after .

sorry to not answer this thread but because of some of the " YOU dumbass " comments I have seen from other threads and I didn't want to hear that

Thanks for the followup Kenny!