overheating 1982 260hp merc

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rplane36

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Sep 2, 2005
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sorry for posting this in the wrong forum earlier but i'm new to forums and will do my best to master this. i sucked up some sand a few weeks ago and thought i got away with it but tried to take it out again and it overheated right away. i cleaned the block running water from the t-stat housing(a little sand came out then ran clean) but i don't know if it can be backflushed or i have to remove the lower unit. i also realize the manifolds probably need cleaning out too and would appreiciate any advise. by the way, no water is coming in
 
Boomyal

Boomyal

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Re: overheating 1982 260hp merc

Not familiar with mercs but what do you mean that no water is coming in. Into where?
 
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rplane36

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Re: overheating 1982 260hp merc

i,m all but sure the impeller/intake is clogged up too,and didn't know if it can be backflushed.i tried running it with muffs but no water reached the block
 
Haut Medoc

Haut Medoc

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Re: overheating 1982 260hp merc

I would take off the drive and stick the appropriate hose size straight into the hole (water inlet) on the bell housing and see if you have water flow, and to see if you over heat. If you do have flow and no over heat then I would take the drive apart and inspect the impeller area, but first I would also look at the screens where the water enters the drive. I'm not sure if there is an effective 'backflush method'. The best thing I can think of is put that hose on the hole on the drive side when you have it off. At least you will be able to isolate where your blokcage is, drive or engine........JK
 
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rplane36

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Re: overheating 1982 260hp merc

thanks for the advice,but unfortunately i don't have a trailer to take the boat out of the water for that type of work. if i can't get to it from the engine compartment then its going to cost me big time. by the way, if it matters, its an alpha I outdrive
 
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elpaso

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Re: overheating 1982 260hp merc

If boat is in the water. Remove the pickup hose at the thermostat<br />housing. Back flush outdrive with garden hose.<br />Raise outdrive and watch for water flow out<br />of pickup holes.<br />At thermostat housing remove the hoses that go to exhaust manifolds<br />and risers, flush out.
 
Don S

Don S

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Re: overheating 1982 260hp merc

Running in sand may have plugged the drives pickup, which may have allowed the impeller to run dry. At that point the impeller would be destroyed after about 15 to 30 seconds of running.<br />No amount of flushing will fix that. You need to pull the boat, pull the drive apart and have a look at the impeller.<br />Trying to run water backwards through the raw water pump won't work very well if the impeller is in good shape.
 
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rplane36

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Re: overheating 1982 260hp merc

thanks for the help,i also took most everyone else's advice and ordered a repair manual
 
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