97 Mercury EFI 175HP Overheating

IDM

Cadet
Joined
Jul 29, 2012
Messages
22
Hi Fellas,

Here is the story. Was out in the boat fishing and the engine shut off. We found it to be a faulty ignition switch.

At the same time the mechanic noticed that my boat didn't buzz when you turn the key to the on position. So he replaced the horn as well with the OEM horn which also goes off if the engine is overheating. This horn hasn't been working for years, because I don't remember the last time it beeped before I'd start the boat.

On our way back out fishing after a few minutes of half throttle the buzzer went off as if the engine were overheating. Engine ran fine but at cruising speed the buzzer would go on and only if I idled for a few minutes would it stop.

So now I'm stumped, is my engine really overheating or is the sensor telling the buzzer incorrect info?

My water pump and thermostats were replaced about a year ago and the engine spits out water just fine.

The mechanic mentioned a poppet valve maybe being the issue, what can I check?

Really appreciate the help!
 
Joined
Jan 17, 2011
Messages
73
Re: 97 Mercury EFI 175HP Overheating

It could be mutliple things......id start by with checking out the water pump. Sounds like a overheat to me. If w/p doesnt fix it id move on to poppet valve.
 

IDM

Cadet
Joined
Jul 29, 2012
Messages
22
Re: 97 Mercury EFI 175HP Overheating

It could be mutliple things......id start by with checking out the water pump. Sounds like a overheat to me. If w/p doesnt fix it id move on to poppet valve.

I replaced the water pump about a year ago along with the thermostats. The engine has low hours on it since then.

how can I check the condition of the pump?

How can I check the poppet valve? Any instructions?

Thanks!
 

Dukedog

Captain
Joined
Oct 6, 2009
Messages
3,440
Re: 97 Mercury EFI 175HP Overheating

how can I check the condition of the pump? Thanks!

Over heat with no clue as whats tha cause. Complete water pump kit first thing. It doesn't have a "shelf life/expiration date". Most of tha time "little use" is harder on tha pump than using every day. Replace poppit while your at it. Not that expensive to do. T-states you can test on tha kitchen stove with multi meter and thermometer. Should open around 140 ta 145 degrees if you replaced with oem stats. You can also check over heat sensor this same way. It should close at no cooler than 190 degrees. Can possibly be well over 200 degrees. They can vary some. Tha coolin' stuff is NOT something to pinch pennies on. Go slow and methodical. Watch water pressure and heat guages if you have 'em (you really need tha pressure guage). Check pee stream and head temp with your hand. If thse things don't fix it you will need ta dig deeper with a lot more involved............jms and GL
 

jarron

Cadet
Joined
Jul 13, 2008
Messages
9
Re: 97 Mercury EFI 175HP Overheating

For roughly a 100 bucks I would put a New water pump kit and 2 more New thermostats. I would hate to see you melt a piston like mine did when the thermostat on the right bank stuck closed.
 
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