| Author |
Message |
    
Robert Wagner
New member
Username: lbwagner
Post Number: 1
Registered: 06-2009
| | Posted on Saturday, June 27, 2009 - 05:18 pm: | 
|
When I run it hard and get on plane, the overheat alarm sounds. We idle a while and the alarm stops.
I've replaced the stats and poppet valve, oil reservoirs are full, water is circulating in the engine. I replace the impellor 2 years ago but with barely any hours on it since.
Now what? |
Graham Lamb
Senior Member
Username: galamb
Post Number: 5478
Registered: 05-2007
| | Posted on Saturday, June 27, 2009 - 08:48 pm: |
|
Check the impellor - even though next to no hours the rubber can still rot from sitting.
Could also be the sensor itself. They are a simple design. As the temp increases, the resistance of the sensor decreases. If it goes down far enough you complete the circuit and get an alarm.
On a motor in this horsepower range it is wise to run a temp gauge as well.
The sensor(s) can be easily replaced but can also be tested as noted below..
 |
IBNFISHN
Advanced Member
Username: ibnfshn
Post Number: 629
Registered: 11-2005
| | Posted on Saturday, June 27, 2009 - 09:04 pm: |
|
Great chart Graham. |
Robert Wagner
New member
Username: lbwagner
Post Number: 2
Registered: 06-2009
| | Posted on Sunday, June 28, 2009 - 08:46 am: |
|
Dang, Graham, this is some useful information. I'm gonna try it.
Yesterday, I replaced the pump and the impellor anyway.
I really appreciate your help with this! |
Graham Lamb
Senior Member
Username: galamb
Post Number: 5488
Registered: 05-2007
| | Posted on Monday, June 29, 2009 - 02:03 am: |
|
They are pretty cheaply built sensors. But to be fair, when they "bust" they cause an alarm and even if it is false that is much better than failing quietly and causing you to fry your motor because the alarm never went off and there really was a problem.
The guardian system on the early Optimax's (and maybe other models but that's the one I am aware of) would reduce your rpms by 25% if it was a failed sensor as opposed to a "detected problem".
I kinda liked that design but Merc scrapped it in 2001 after only producing it for a few years - too bad they didn't improve on it (maybe it really hilited how crappy the sensors are (???) 
Anyhow, depending on the model the sensors normally sell for between 25-50 bucks, but I wouldn't run a motor without them... |
