Texasmark
Supreme Mariner
- Joined
- Dec 20, 2005
- Messages
- 14,795
Was looking at the wiring on this engine; safety sensors in particular (oil/over temp).
Saw a tan/blue stripe wire from the over temp sensor on the starboard bank of cylinders (head/water jacket cover) that went to a junction box and then thru the output engine connector to the warning horn. Got out my service manual and it checked this and all was fine. Got out the shorting wire, shorted it (to ground like the ot switch does) and sure nuf got the warning light and buzzer.
Looked at the port side and there is a brown wire that went straight to the wiring harness but not to the connector, rather a brown wire that was dressed along side the connector in the output wiring harness.
Went to the service manual, found the wire in the wiring diagram, and this wire went up to the dash area. Showed to have no terminating point (just a dangling participle...grin). Hmmmm started wondering what's going on.
Had the dash out working on the tach later and noticed a brown wire with a red blob of insulator material on the end of it connected to nothing. Hmmmmmmm.
Sure nuf, this was the the wire that the port bank over temp sensor was connected to. Forget the tach for the moment; went back to the thermal sensors.
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Now, this engine has 2 banks of 3 cylinders and at the top of each bank is a thermostat (2 per engine). So the brain says that if the over temp sensor on the port side is connected to an unterminated wire, if the port thermostat sticks shut (which they have proven to do for me twice in other engines) then you ainta gonna know it till the engine siezes (like one of mine did before the days of the temp sensor) and presto you are in for an OH.
So I pulled the wire, cut it off the bayonet terminal, attached a terminal lug, and put it on the junction box with the other one.
Now if either bank overheats, the alarm and visual dash light warn me.
If you have one of these critters you might check out your wiring. This is not an error. These wires have not been tampered with. Might send Merc an email and see if they overlooked a stuck stat type of problem with their wiring scheme.
Only thing I can figure is that the Merc engineers were warning for an impeller malfunction or something of the sort, that would affect the entire engine, not a stuck thermostat that could occur on one side only. I assume the brown wire was for a dash light (since it is an open closed switch, not an analog resistor to drive a temp meter) that some may want on their boats.
Mark
Saw a tan/blue stripe wire from the over temp sensor on the starboard bank of cylinders (head/water jacket cover) that went to a junction box and then thru the output engine connector to the warning horn. Got out my service manual and it checked this and all was fine. Got out the shorting wire, shorted it (to ground like the ot switch does) and sure nuf got the warning light and buzzer.
Looked at the port side and there is a brown wire that went straight to the wiring harness but not to the connector, rather a brown wire that was dressed along side the connector in the output wiring harness.
Went to the service manual, found the wire in the wiring diagram, and this wire went up to the dash area. Showed to have no terminating point (just a dangling participle...grin). Hmmmm started wondering what's going on.
Had the dash out working on the tach later and noticed a brown wire with a red blob of insulator material on the end of it connected to nothing. Hmmmmmmm.
Sure nuf, this was the the wire that the port bank over temp sensor was connected to. Forget the tach for the moment; went back to the thermal sensors.
-----------------------------
Now, this engine has 2 banks of 3 cylinders and at the top of each bank is a thermostat (2 per engine). So the brain says that if the over temp sensor on the port side is connected to an unterminated wire, if the port thermostat sticks shut (which they have proven to do for me twice in other engines) then you ainta gonna know it till the engine siezes (like one of mine did before the days of the temp sensor) and presto you are in for an OH.
So I pulled the wire, cut it off the bayonet terminal, attached a terminal lug, and put it on the junction box with the other one.
Now if either bank overheats, the alarm and visual dash light warn me.
If you have one of these critters you might check out your wiring. This is not an error. These wires have not been tampered with. Might send Merc an email and see if they overlooked a stuck stat type of problem with their wiring scheme.
Only thing I can figure is that the Merc engineers were warning for an impeller malfunction or something of the sort, that would affect the entire engine, not a stuck thermostat that could occur on one side only. I assume the brown wire was for a dash light (since it is an open closed switch, not an analog resistor to drive a temp meter) that some may want on their boats.
Mark