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Over heat alarm on saltwater series Merc 150

  • Thread starter Christopher Cavanagh
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Christopher Cavanagh

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"I have a 2003 150 hp saltwate

"I have a 2003 150 hp saltwater series merc outboard. At low rpm's, the engine runs normal and indicates around 4 psi of water pressure. When I go to bring the boat up on plane, around 3500-4000 RPM, the overheat alarm sounds and the water preasure gauge indicates around 8-10 PSI. When I reduce back to lower RPM'S (1000-1500) the overheat alarm stops sounding after about 30 seconds. I was thinking of starting with the impellor. Any ideas's? Thanks!

Chris"
 
"Christopher,
I have a Mercu

"Christopher,
I have a Mercury 150hp black max with the same problem when i plane out to 3000 rpm's i get a alarm just like yours. have you had any luck trying to fix your problem. I was going to check or even maybe changing the sensor today. please let me know if you fixed yours. Thanks"
 
"HI MINE acted the same way ex

"HI MINE acted the same way except alarm overheat buzz is on after 5-10 minutes running, water pee hole first start then stop after running for 10-15 minutes ??? advise ! Thanks"
 
"Bad impeller, seal/gasket sho

"Bad impeller, seal/gasket shot - when was the waterpump last serviced?

If the answer is anything other than this year or last year it's overdue...

It may well take 5 to 10 minutes for the motor to heat up enough to "overheat"..."
 
"I have a 2004 150h.p. saltwat

"I have a 2004 150h.p. saltwater Merc with an overheating problem. Under 2000rpm's, no high temp. alarm. At 2000rpm's the temp. shoots right up. At 3000rpm's and above it's back to normal range. Any ideas??}"
 
"Bruce, poppet is starting to

"Bruce, poppet is starting to go on you by the sound of it - about 20 bucks worth of parts and less than an hour of your time..."
 
"Thank you for your response,p

"Thank you for your response,poppet valve and water pump were both changed this season. Any other ideas?}"
 
I had the same problem with my

I had the same problem with my Black max when i reached 3000 rpm's i would get an alarm. This weekend i went down to the boat a checked the wiring unpluged the quick connects cleaned them and put them back tightly i then took the boat out at 4000 rpm's the alarm did not go off. Check your wiring. Good luck.
 
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