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Yamaha 50hp 4Stroke alarm

M

martino

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"I have a 1999 Yamaha 50hp 4-s

"I have a 1999 Yamaha 50hp 4-stroke with only 280 hrs on it. I change the oil and plugs each season. The water pump was replaced last year with what is supposed to be Yamaha's 'improved' impeller. It ran fine the rest of last summer. This summer a steady alarm sounds at low speed then shuts down the engine rpm, but not off. The oil and overheat lights always stay off. There is a good stream of barely warm water flowing out the back of the engine. When I turn off the key and allow the engine to stop then turn it back on the alarm will stay off until I restart. At low speed (pulling away from shore, no wake zones, etc.) it usually goes back on. If I can get it up to 4000 rpm or more before the alarm goes back on, it tends to stay off until I go back down to low speed. My local Yamaha sales and mechanic appears lost. I would appreciate your help."
 
"I'm thinking it's a b

"I'm thinking it's a bad thermo on the block. Aren't there 2?... one at top port side and one at bottom stearn? The alarm seems erratic and has gone off at odd times, sometimes within seconds of starting when the engine is still cold. Yesterday it didn't go off at all. ASSUMING it's only one of them, what do you think about buying a sensor and switching out one position, and if the alarm still goes off I switch the other? If I'm right I should find the bad one.....no?"
 
"all u have is an oil pressue

"all u have is an oil pressue and 1 temp, acording to the factory

anything with a pink wire is part of the alarm"
 
"The motor is a 4-stroke 50HP

"The motor is a 4-stroke 50HP T50TLRY, with a tag saying it was made 5/99. At the lower rear of the motor is a nickel-sized black sensor with 2 blue wires. Do you know what this one is for??? There is another just like it at top port side, but I do not recall its wire color (I'm home the boat at the cottage). It could be pink. I'll check and disconnect to see if it quiets the alarm."
 
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