2005 200hp OX66 Overheat

[codym92]

I have a 2005 OX66 that throws an overheat alarm when idling for extended periods. I can throttle it up to a fast idle or run it and never get an alarm though. I have changed the poppit valve, thermostats, and a new oem lower unit was put on last year (Was told they come with new water pumps). I checked the water pump tonight just to verify and everything looked brand spanking new (impeller and all components around it). Any ideas on what my problem might be or where I might try trouble shooting next?

Thanks!

[jkainoa]

I've got a 2000 200hp OX66. I've had the same problem in the past.......Didn't like to idle or even run at low speeds. I'm confident my issue was my water pump. It's been fine every since I replaced it. Sorry I couldn't be of more help. Good luck.

[21XDC]

I had this issue, It was my temp sensors were triggering at a lower temp than specs. I removed and tested them in a pot of water on the stove, temp gauge, and continuity tester.... I replaced the sensors and all is well again.

[codym92]

Any idea at what temp they should be going off?

[JoeFriday]

What is your water pressure at idle? If it is below 5 psi at idle and does not move to around 10 psi at 1100 rpm, it still could be your water pump. Yamaha tweaked the housing design. If that is it, do a complete update of everything on the pump. Simyamaha.com has a complete kit that includes the housing. Torque everything down to spec and check it again. That's what fixed the same problem for me. I had barely measurable water pressure at idle before and 5 psi after. Mind you I would jump up to around 20 psi running before the change, so everything looked fine except at idle.

[codym92]

I actually don't have a water pressure gauge on it at the moment as I just bought the boat not too long ago and it wasn't equipped with one. I just bought one but I haven't had a chance to figure out how to install it yet. Has Yamaha updated the water pump design since last year? Like I said, it had a brand new lower put on it about a year ago. The water pump looked near perfect; none of the vanes seemed damaged/worn

[jkainoa]

What is your water pressure at idle? If it is below 5 psi at idle and does not move to around 10 psi at 1100 rpm, it still could be your water pump. Yamaha tweaked the housing design. If that is it, do a complete update of everything on the pump. Simyamaha.com has a complete kit that includes the housing. Torque everything down to spec and check it again. That's what fixed the same problem for me. I had barely measurable water pressure at idle before and 5 psi after. Mind you I would jump up to around 20 psi running before the change, so everything looked fine except at idle.

This is exactly what I did. I bought the whole kit from Sims. I think it was just over 100.00?? It even appeared that the tell tale stream was stronger afterwards. However I do agree that if you had a new lower unit put on, that shouldn't be the issue. But there's nothing like doing something yourself......That way YOU KNOW it was done. If you do decide to do it, there's a great step by step tutorial on here walking you thru it from beginning to end. I think the temp sensors are pretty reasonably priced too and seem easy to do, so maybe you could start there first?

[HookedAgain!]

Might look at the poppet valve as well. dirt gets in there and clogs it up, doesn't take much!

[codym92]

New poppit kit was installed 2 weeks ago. Andy at Simms suggested I test sensors to make sure it is actually overheating and not just a faulty sensor. I'll try that first.

[21XDC]

Search for my post... I have all the info included.

[JoeFriday]

What is the brand of the new lower? You might check the thermostats to see if the are opening or just replace them. Popped like mentioned could be another culprit.

[codym92]

Yamaha oem lower. Thermostats and poppit already replaced with brand new parts 3 weeks ago.

[21XDC]

>>>>>>>>> http://www.bbcboards.net/showthread....dc#post4020656

[JoeFriday]

Without a water pressure gauge, it hard to say the pressure is fine. You could pull your thermo switches like 21xd suggested and test to see if yours go off at 181 degrees.

[codym92]

So I finally got around to testing my temp sensors today and one went off at about 178 and the other about 158. I'm guessing I probably need to change the one that went off at 158... How critical is the 181 spec; should I change the 178 sensor also? Just out of curiosity, what is the typical operating temp for these motors?