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BF75A temperature alarm problem sensor

tknorth

New member
"Greetings all, yesterday, aft

"Greetings all, yesterday, after a couple of hours running gently around a local clean fresh water lake, and a brief spurt at 3000 RPM I slowed for about a minute then put the engine astern. The temperature alarm on the remote immediately lit up and the alarm buzzer sounded continuously. The oil pressure light remained a solid green. I reduced to idle, the temperature light remained lit, as did the oil pressure green light. The coolant discharge was pumping healthily. I switched off, left the engine for 10 minutes, then switched the ignition on - without starting the motor. The temperature light lit and stayed lit. I started the engine - at idle the temperature light is lit, but no buzzer, at 1100 RPM the light is still lit, and the buzzer is yelling at me. The outlet temperature at the observation discharge is "hand warm" only, and the engine is in all respects (to my untrained eye!) normal. I was able to motor at 3kts the 4 miles back to the slip. The engine coolant discharge stayed "hand warm" and all was normal - except the temperature light was lit continuously and the buzzer went off as I nudged it over 1000 rpm going astern at the slipway. The inlet filters were found to be perfectly clean, the engine temperature cool and uniform. The Temperature light comes on immediately when the engine is cold this morning when I turn the key without starting the engine. I'm hoping this is just the temperature sensor but would really welcome some advice - and if it is the sensor - is this a standard Honda "automotive" type component or is there a special "marinized" one -I cant find it in any parts listings !
The engine has 120 hours on it, has only been run in fresh water, and has been regularly and well maintained.
Many thanks for reading to the end !
All the best
Trevor"
 
"Many thanks Jamie, I'm or

"Many thanks Jamie, I'm ordering up a spare today. Would the discharge water from the "pee hole" be at an elevated temperature, or even not running at all, if the thermostat was faulty ? (I'm thinking like a car mechanic here i know, so I'm probably way off)"
 
"The Pee hole is separate syst

"The Pee hole is separate system that bleeds air from the water jacket. The t-stat regulates the temp. If the t-stat does not open, it will cause the water temp to run hot. Usually the t-stat will fail in the open position causing the motor to run cold. The removal of the t-stat is very easy two bolt job, you might want to drop the t-stat into vinegar for a couple of hours to dissolve the crud. The discharge water from the pee hole should not run warm unless you have been at speed for a period of time. I'm guessing you have reduced water flow due to a bad impeller."
 
"Thanks for the good advice -

"Thanks for the good advice - I started the engine with the bottom half in a big tub of fresh water, the temperature light came on after 1.5 minutes and the head felt hot.I tested the thermostat with water at 90C, and it didnt open. So I dropped the thermostat into vinegar and all the calcium crud dissolved in about 30 minutes. hey presto, it now works, opening at 72C as the stamping on the bottom of the stat advertises. I'll get a new one though, better safe than sorry.....
The outflow from the pee hole seems good and strong, and the engine runs cool, without alarms, with the thermostat removed, so would I be correct in thinking that the impeller is probably OK ? I'll run for a while without the stat (my nearest outboard shop actually advises removing and chucking the stat away from Honda engines! not too sure about that move....) Its a pretty major task here in the boonies to get the engine torn apart to replace the impeller - especially when I NEED to go fishing :)"
 
"I would not run without the t

"I would not run without the t-stat. The motor is built to much closer spec's that the old days. The motor needs to get up to temp in order to develop full horse power and burn the fuel completely. You can order the parts you need online. Try
http://boats.net./
Nick"
 
Trevor - Nick is absolutely co

Trevor - Nick is absolutely correct. You should NEVER run a 4-stroke marine engine without a properly working t-stat installed. Doing so will often cause a number of long term problems with the engine - every thing from fouled plugs to gas-diluted oil.
 
"Nick and WD, Thanks a ton for

"Nick and WD, Thanks a ton for the very sound advice. Its great to have a forum like this - it seems that not every dealer has our best interests at heart ! All the best."
 
"Trevor,
I am glad to help ou


"Trevor,
I am glad to help out a fellow boater. I have had so much difficulty trying to work with the dealers that I prefer to just do it myself. I have learned a lot with the help of this forum and others. I Think it would be a good idea to pull your t-stat to clean or replace each time your change out the impeller.
Nick"
 
Best to start your own thread with your story, give us your engine age, hours, fresh or salt water, maintenance details, any and all details/work done on the engine. If you tap on the above posters name’s you’ll see that they haven’t been on the forum in a long time.
 
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