2004 Mercury 90ELPTO Overheat Alarm

[Rods Of Fury]

I am having an issue with my outboard overheating. When I run it in the driveway with the muffs on, it only takes about five minutes of idling for the alarm to sound. I am getting water out of the tell tale sometimes, but not always. I just replaced the impellar hoping that was the problem, but it is still doing it. I am going to bring it to the river one of these days and see if the muffs just dont give it enough water. I noticed that the water coming out of the tell tale does get pretty warm. When I unhook the temp sensor the alarm goes off. I also noticed that water is coming out the center whole of the prop, not sure if that is normal or not. Could it maybe be a bad thermostat? I unfortunately dont know too much about outboard motors. If anyone can help me I would greatly appreciate it. Thanks

 

[racerone]

Re: 2004 Mercury 90ELPTO Overheat Alarm

Test it on the river.---Could be not enuff water from the hose or too much air in tap water.

 

[Rods Of Fury]

Re: 2004 Mercury 90ELPTO Overheat Alarm

I got the boat out today, and all is well. There just must not have been enough flow or whatever from the hose. I feel like a wieght has been lifted off my shoulders!! I was pretty nervous

 

[Texasmark]

Re: 2004 Mercury 90ELPTO Overheat Alarm

Glad it was just operator error. Ha! On the water out the exhaust question, that's normal. That's where the engine cooling discharge and mid section cooling water exit the engine. On that engine you can have pee and a bad stat too. Pee is plumbed off the exhaust manifold cover where a continuous flow of water, non-regulated, keeps the exhaust from burning the paint off the cover and all.

The block is controlled by a t-stat with an opening temp of 143F up to 2500 rpms. Above that, water pressure forces a high volume valve called a pop-off, or poppet off it's seat and allows for increased flow at the higher rpms. The OT alarm occurs when the OT sensor sensing block water hits 195F and extinguishes at about 175.

The fact that you had intermittent pee on muffs is surely indicative of too little cooling water supplied to the engine. I have the '02 version of that engine.

Mark