150 hp overheat alarm

I have a 2006 150 hp honda tha

I have a 2006 150 hp honda that the overheat alarm goes off when I hit 5300 rpm's. I shut it off and I can run again. As long as I dont go over 5300. The marina has run out of things to change and I am running out of money. Any idea's

"You did not say if it has run

"You did not say if it has run ok on this boat before. Also, has there been any change to the boat or the motor since it was performing correcly.

Is the boat riding any differently that could cause the water pickups to not get enough water when you are above 5300 rpm.

What have they done so far? I assume the standard water pump change. Did they change the entire pump assy? Anything else?

There are four engine coolant temperature sensors on the 150. Did they take the boat out and make it happen with the handheld computer on it? If they took a couple of snapshots, they should at least see which sensor is out of range.

Have they changed thermostats? There are two, one for the head and one for the block. Both are different temperatures. Mixing them up can be a problem.

Really need more into..."

"I bought the motor new. ALway

"I bought the motor new. ALways ran fine. No changes to the flats boat. Changed the water pump complete. thermostats have been changed 4 times this year. Sensors have been changed. They took the boat out and made it overheat with the computer on. It showed which sensor it was. Changed case kit, manifold gasket, cover kit. Motor has 1100 hrs on it. Motor has always been serviced by a honda mech. They dont know what to do next. Thanks for the reply Mike. I am very frustrated."

"Here is a long shot... Since

"Here is a long shot... Since they have been looking at the flow from going in to circulation, how about a slight blockage going out. Have they looked into the relief valve in the exhaust system? I am not sure if this could cause the problem, but it may not allow the excess exhaust and water out if it is partially clogged or stuck. It may need that extra flow at top rpm.

I would have to think that they have checked all passages through hoses, etc. If kinked or collapsed...can cause a problem.

Like I said, it is a real stretch!"

"Hmmmm. Interesting problem. N

"Hmmmm. Interesting problem. Never worked on a 150, so I'm no expert like Mike. But, it seems obvious you probably have a water circulation restriction. Just for grins, I would start the diagnosis by pulling off the water pick up screens and see if there is any obstructions. Maybe even try to run it with them removed just to see if that may be the problem. Then a high pressure back wash from the t-stats, and a strong dose of salt-away or similar in the process."

Thanks for the reply's. I

Thanks for the reply's. I will forward all to my mech. And as soon as we find the problem I will post.

"Finally got it fixed. At the

"Finally got it fixed. At the end of the main waterpump tube, there is a rubber grommet, it was soft and full of dirt and salt. He replaced it and cleaned it. Now my water pressure gauge goes up to 20 psi. It only went to 5 before. Thanks guys."