Hello all, This is my first post to the forum, I'll try to be as thorough as possible. First, the info:
2014 Larson LX195S - first owner
4.3 TKS (190)
Alpha 1
High Five 19P
75 hours
Used freshwater only - premium (94 octane) fuel
Problem: intermittent sounding of overheat alarm
Diagnosis progress so far:
Thanks to all the info elsewhere on this forum, I've learned a lot about this issue.
The alarm sounds intermittently when engine is at operating temp, and is a somewhat random pattern of beeps from the alarm - sometimes short blast, or series of varying duration beeps, sometimes longer steady... Occurs in calm or rough waters, when towing or cruising. Never at idle or slow speeds.
Disconnecting the sensor connector with the yellow and black wires at the base of the thermostat stops the alarm. Tried new sensor same problem. Gauge reads normal - never goes over 170, usually runs 160- 165. Verified temps with infrared thermometer, took readings several locations around thermostat (while duplicating operating conditions that would trigger the alarm) all normal, corresponds to gauge.
When alarm sounds, there is no drop in performance, engine always runs great, starts easily warm or cold, good power, smooth idle etc.
the boat is under warranty, but I'm reluctant to take it in - intermittent problem that will only occur under load at higher RPM 4000 to 4500. So, it will be hard to diagnose for the dealer. Besides, I don't mind spending a few bucks and fixing it myself, I prefer working on my own toys.
So, a couple of questions if I may: what else is on that sensor circuit? The wiring diagrams I have been able to find are pretty vague and appear to have some errors (ie incorrect sensor names, etc) is there anything else that is seeing the signal from the sensor enroute to the alarm that I should check? Are the latest manuals from Mercruiser better / more accurate than what's available for download online?
I should note TKS works normally with sensor disconnected. You can hear the sound of the air bypass when cold, quiets down as engine warms up. Idle speeds normal.
FYI I'm an old GM dealer tech, worked on these engines for years in light trucks and have been around cars and boats all my life. This engine is not overheating.
Any tips on testing these temp sensors in hot water? I tested the two I have (original and new one I bought) and both seem open until water is around 195. What ohm scale should I use for this test? Should they be open right up until they reach closing temp, then close, or do they show some gradual decreasing of resistance as they warm to the point there is enough current flow to set the alarm?
Any help would be appreciated, including suggestions for things I may have overlooked or different tests etc. I hate running around with that sensor disconnected - it's there for a reason.
Thanks all
2014 Larson LX195S - first owner
4.3 TKS (190)
Alpha 1
High Five 19P
75 hours
Used freshwater only - premium (94 octane) fuel
Problem: intermittent sounding of overheat alarm
Diagnosis progress so far:
Thanks to all the info elsewhere on this forum, I've learned a lot about this issue.
The alarm sounds intermittently when engine is at operating temp, and is a somewhat random pattern of beeps from the alarm - sometimes short blast, or series of varying duration beeps, sometimes longer steady... Occurs in calm or rough waters, when towing or cruising. Never at idle or slow speeds.
Disconnecting the sensor connector with the yellow and black wires at the base of the thermostat stops the alarm. Tried new sensor same problem. Gauge reads normal - never goes over 170, usually runs 160- 165. Verified temps with infrared thermometer, took readings several locations around thermostat (while duplicating operating conditions that would trigger the alarm) all normal, corresponds to gauge.
When alarm sounds, there is no drop in performance, engine always runs great, starts easily warm or cold, good power, smooth idle etc.
the boat is under warranty, but I'm reluctant to take it in - intermittent problem that will only occur under load at higher RPM 4000 to 4500. So, it will be hard to diagnose for the dealer. Besides, I don't mind spending a few bucks and fixing it myself, I prefer working on my own toys.
So, a couple of questions if I may: what else is on that sensor circuit? The wiring diagrams I have been able to find are pretty vague and appear to have some errors (ie incorrect sensor names, etc) is there anything else that is seeing the signal from the sensor enroute to the alarm that I should check? Are the latest manuals from Mercruiser better / more accurate than what's available for download online?
I should note TKS works normally with sensor disconnected. You can hear the sound of the air bypass when cold, quiets down as engine warms up. Idle speeds normal.
FYI I'm an old GM dealer tech, worked on these engines for years in light trucks and have been around cars and boats all my life. This engine is not overheating.
Any tips on testing these temp sensors in hot water? I tested the two I have (original and new one I bought) and both seem open until water is around 195. What ohm scale should I use for this test? Should they be open right up until they reach closing temp, then close, or do they show some gradual decreasing of resistance as they warm to the point there is enough current flow to set the alarm?
Any help would be appreciated, including suggestions for things I may have overlooked or different tests etc. I hate running around with that sensor disconnected - it's there for a reason.
Thanks all
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