buzzer goes off after 6 min,20 sec.

50 h.p. outboard merc , 2005 ,tell tale is discharging water good, alarm comes on after 6 min, oil is full, i cked continuity between wires off oil tank, dont have continuity, i was told i shouldnt. thanks in advance.

Should be the basic resistance alarm that only checks for over heat or out of oil (low oil). If the temp sensor reads "hot" it loses resistance and allows the alarm circuit to go to ground and "beeeeeeeeeeep". Likewise with the oil sensor. It's just a float - when the float touches the bottom of the tank (sensor), it completes the ground circuit and "beeeeeeeeeep".

If it was going off as soon as the motor was started I would suspect a bad float in the oil tank. Since it takes a few minutes that kinda sounds like the temp sensor is reading "hotter" than actual temp. As the sensor warms up it starts "losing" resistance - too much heat = no resistance.

Have a look for the sensor - located just below (or beside) the top cylinder on the (head) water jacket cover - follow the tan/blue wire coming from it to it's bullet connector and unplug it.

If your beep goes away I would replace the sensor (sender I think it's called on the parts list). There may be an inclination to simply leave it disconnected. I would do that if I was at a remote location to simply cure the alarm but it should be replaced if it's the problem. An over heat will toast the motor.

If it was the oil level sensor I could live without that - simply make topping up the oil before every outing a part of the routine.

Of course it really could be an overheat. Just because it's pumping from the tell-tale doesn't mean that you don't have a clog somewhere in the water channels. BUT, the temp sensor (sender) is a known issue. They get old, they quit working - they are not a high tech piece of equipment and do fail.

Replace the impeller.....

thank you galamb, i just added oil to fuel, and ran it, unplugged wires off tank while running it, this may sound like dumb question but even though the water is flowing thur 2 cycle engine should the water coming out of tell/tale be that hot ! dam its hot, im running water out of a well at a idle, ha, i will get that temp senser tomorrow and do a back flush of system or flush it once i find out correct way to do that, ya your right on the money , many thanks, from u.s.a., wisconsin somewhere.

ya, ! water is coming out of tell tale real good,

ya, its been 6 years since i picked this outboard up or rather had it installed , the buzzer failed on owner and burned pistons so M&W marine changed them out and i had good luck last 6 years with her, i have done two so far on other outboards isnt real expensive. thank you

Impeller need changed every 2 years no matter the usage or lack of.

ok , im off to get a another look at this temp senser and impeller i tk was 16 bucks last time i changed it was prob 5 years already.

got the merc apart and the impeller was fryed , cant belive it was pumping any water, there is a nylon washer on one side id call that the bottom side, but the top side nothing that side was really burned up, the woman at boat shop says the washers arent available, hm, i did try to find a nylon washer at hardware store but no luck, any ideas

go check the parts list. https://www.mercurymarine.com/en/us/parts-and-accessories/parts-catalog Check for the items and get the parts numbers and search if you can.

thank you, i think i found them in milwaukee but i will double ck with that i.p.,address thanks

is that cool, i entered my serial nbr, and went down the list i found the part nbr of washers, both carry same nbr, ha, thats way cool site, i have four coming from m-w marine out of hales corners wi. she only wanted a buck a piece, lady here in bonduel wi, at the sport shop wants 9 bucks ea, ha, and american marine here in shawano, drum roll please, he wants 22 bucks for each washer,ha, hm, nothing like screwing the public, thanks again