2001 OX66TXRZ Overheating Issue

[Pelagiholic]

Prior to the last SKA tournament I noticed that my OX66 would start overheating when placed in gear and low idled (approx. 500-900rpm). I immediately purchased another new water pump and installed it. This did not seem to remedy the situation so I further replaced the two thermostats. While out of Sebastian pre-diving some lobster spots I noticed that it was happening again.

Any thoughts? Am I overlooking something?

[pete28]

Check the popit vales

[Ken]

'holic,
The pressure control valve, aka pressure relief valve, poppit valve, is designed to open at around 20 psi to relieve over-pressure in the cooling system. When this happens, water will dump out the relief holes at the top and back of the upper casing. You should see this if your water pump is strong and motor above 3000 rpm.
At lower rpm, there should be very little water coming out the relief holes - if there is more, then the prv may have debris between the rubber head and seat. Pre-mature dumping of this cooling water can lead to motor over-heating.
If you replace the prv, ask for the new "mushroom" style that is less prone to sticking open from debris collection.
Now, assuming your water pressure is good (5 psi at idle and 20+ above 3000 rpm) and thermostats are good, and prv is doing its job, if your motor is still overheating, then only thing left is clogged head water jackets. The heads have to be removed and jackets cleaned out.
Good luck [img]smile.gif[/img] ,
Ken K

[Pelagiholic]

I looked on the Yamaha Parts page provided here at boats.net but could not find the part. Could someone a obviously more mechanicaly inclined help? It is a 2001 Yamaha SX250TXRZ.

[Ken]

'holic,
Here's a link to the diagram of your motor from the online catalog above - item #19:

http://www.boats.net/yamaha/partsyst...mponent=340544

Good luck [img]smile.gif[/img] ,
Ken K

[Pelagiholic]

Thanks Ken.

Is the pressure relief valve readily accesible? It looks as though there are only two bolts holding it on. Would I have to take off alot of other stuff to access this component. For example, I thought changing the Thermostats was simple; is the pressure relief valve just as simple?

Thanks again Ken, you have been very helpful.

[flytact]

This is how I do it on my 225.
To remove the popit you'll need your 1/4" socket set and longest metric socket. It sits down below the edge of the engine rim making it tricky to get to. You'll then need to free up some of the "stuff" that's in the way. If I'm getting too technical I'm sorry. Remove the two bolts and the PCV will "pop" out due to the spring. Get a toothbrush and clean everything really well. Putting it back is rather tricky, easy if you have three hands. You'll need to compress the spring, hold the cap and find the bolt hole. Patience.
This was exactly the reason for some overheating issues I was having.