Mercury 75 ELPTO Question

[jac714]

OK like an [PoorWordUsage] I ended up running my engine for about 15 seconds dry and fried the impeller. I am in the process of replacing it but have a few questions:

1) Do I need to replace the shaft seals? I know I have to replace the water pump gaskets but do I need to take remove and replace the seals at the bottom of the shaft?

2) The over-temperature alarm is activated and will not turn off, I have to find the engine temperature sensor, does anyone know where it is on this motor?

3) Any pitfalls or problems I should watch for?

Thanks in advance for any help or advise?

[boatfixer]

No, you dont need to replace the seals.

Look on the back of the block for a sensor that has a tan wire, thats your temp sensor. It sounds like it may have been hot enough that sensor is now shot which means I would want to do a compression test just to make sure there is no damage to the engine.

[jac714]

No, you dont need to replace the seals.

Look on the back of the block for a sensor that has a tan wire, thats your temp sensor. It sounds like it may have been hot enough that sensor is now shot which means I would want to do a compression test just to make sure there is no damage to the engine.

Could it reasonably get that hot in less than a minute at idle? It had been shut off for about an hour and was not over heating before this? I can (and will) certainly do a compression test but am curious if these engines run that close to overheating.

Thanks for the idea and information, as soon as I get it done I will report on what happened.

[boatfixer]

Maybe, maybe not. Quick comp check will put your mind at ease tho.

[jac714]

Maybe, maybe not. Quick comp check will put your mind at ease tho.

That is a very good point.

I will do a comp check.

[jac714]

I checked the sensor and it is fine, it has infinite resistance when cool and when put into hot water the resistance drops. I am now facing the problem of whether it is a bad wire (short)(currently the wire measures 11.72 kOhms to engine ground) or the alarm module. One problem I have is that I cannot find the alarm module on the engine. Is it usually mounted with the key-switch and alarm sounder?

I am pretty good at electronics and electrical stuff but i cannot find this to save my life. Any help is greatly appreciated.

[boatfixer]

The alarm module is located on the starbord side of the block. It is square and will have blue, tan, purple and a black wire.

Easiest way to isolate the sensor is to unplug it while the alrm is sounding, which from your earlier post, sounds like it is? If the alarm quits then youve found the problem. You can also do the same with the blue wires from the oil tank.

[jac714]

I have done that for the temp sensor, I am pretty sure the fult is with the module.

Thanks

[jac714]

Compression is 120# in each cylinder so I think I am ok on that. I am still having problems with the alarm but being an old Navy ET I should be able to fix that. Hopefully tyhe weather will hold today so I can work on it.

[jac714]

Final Report, it turned out to be the warning module so after replacement of that and doing the impeller I am back to having a boat again. Thanks to everyone who offered help.

Have a great weekend.