Warning buzzer (overheating?) at idle

[titusj]

I've got a '99 ox66 225. The horn has gone off several times over the last few weeks (indicating either an overhead or a problem getting oil). I'm fairly certain the cause of the horn is temp related, although I don't have a temp gauge to say for sure. The oil res shows everything it should and other things seem to lean toward temp.

The problem has only presented itself when I've been at idle for a short while (it happened when I was letting my motor warm up by the dock on Saturday). After waiting for a while things are OK and I can take off just fine. I haven't had the buzzer go off when I'm on plane at all, only at idle.

I acquired the motor in the fall. The dealer replaced the water pump at that time, so I think that should be fine.

I replaced the thermostats because they weren't opening fully until well over 140 degrees, thinking that was the problem. At the same time I cleaned the poppet (only a few grains were in there). That was before Saturday when it went off again.

Before I went out on Saturday I let it idle with the muffs on for quite a while with no buzzer, so I thought I as ok. I don't have water pressure at idle with the muffs or in the lake, but I understand that is sometimes that case. When I first changed the thermostats and cleaned the poppet valve, I did have a few pounds at idle though. When I'm on plane I have adequate pressure (15+) although I thought I had a bit more right after that work (20 ish). The pee stream always seems to be fine.

A friend suggested checking the plugs to make sure they are the right ones (I intend to do that tomorrow when it is light out).

How can I confirm the warning is from temp and not oil? Is there anything else I should be checking within the cooling system? What is the story with the pressure at idle? Should I be concerned about not having any? How hard is it to install a temp gauge (the boat is a Ranger 519 if that matters)?

Any information you can provide would be very much appreciated. Thanks in advance.

Jason
Brooklyn Park, MN

[titusj]

I removed the thermostats and poppet today. There were small bits of sand in the thermostats and a couple pebbles on the poppet. After getting everything put back together, I had some water pressure (2 pounds) with the muffs on again.

My plugs are correct as per the manual.

Can someone tell me what that poppet does??? I understand that the thermostats open to let water flow when the temp gets high enough, but I don't have a clue what the poppet is for. I read that there is a new "mushroom" design. I don't have that type, but will be getting it soon. Could that simple piece fix the problem?

Thanks again for your help.

Jason
Brookln Park, MN


Modified by titusj at 8:11 AM 7/5/2006

[john tr 21]

i have had the same problem before , it was at a to low of a idle rpm in neutral, so not enough h20 pressure to cool the engine , increase your idle speed and the problem will be fixed.

[titusj]

Well this weekend I finally got the new poppet valve installed. I now have pressure at idle ( a little over 600 rpm). I didn't get a buzzer after two full days of fishing. In addition, I'm now well over 20 pounds at WOT. I think that did the trick for me.

Thanks.

Jason