1982 120 hp mercriser i/o overheat

[jamowers]

I overheated this motor and fried the impeller a couple of weeks ago. I just got it back after impeller change and shift seal replacement and it still overheats at WOT. It is fine at cruising speed or idle. I back flushed to clear any debris in the engine. It is getting cool water from impeller but it seems it cant keep up. Unsure of where to turn next? There are no kinks or obstructios in the seawater line feeding the engine. Any ideas?

 

[woosterken]

Re: 1982 120 hp mercriser i/o overheat

check the thermostat?

woosterken

 

[jamowers]

Re: 1982 120 hp mercriser i/o overheat

Replaced the thermostat. I am changinf the belt on the motor side water pump. I hear a squeal from it almost every time i take off. It is as tight as it gets and has some play. Other than that I'm lost as what else to check.

 

[lucky7's]

Re: 1982 120 hp mercriser i/o overheat

Well yea could be sliping at high rpms....also what about water pump housing? they wear out too...

 

[jamowers]

Re: 1982 120 hp mercriser i/o overheat

How would I know the housing is bad? Are we talking the motor water pump?

 

[jerryjerry05]

Re: 1982 120 hp mercriser i/o overheat

It almost impossible for the circulation pump to be bad unless it's leaking.A motor that old the problem is probably the riser is clogged.26 years is a long time on a man/riser.You can back flush all you can and it still won't help.Jerry

 

[jamowers]

Re: 1982 120 hp mercriser i/o overheat

I changed the belt and at a minimum no squeal!. It idles around 140 I ran it at 3/4 speed for about 4-5 minutes and it kicked up to 160 or so. What is normal operating temp for this thing?

 

[jerryjerry05]

Re: 1982 120 hp mercriser i/o overheat

Most Mercruisers 160 Jerry

 

[chiefalen]

Re: 1982 120 hp mercriser i/o overheat

Anything below 190

 

[jamowers]

Re: 1982 120 hp mercriser i/o overheat

Quite a range! Is there an easy way to check riser and or manifold for restriction without pulling them?

 

[chiefalen]

Re: 1982 120 hp mercriser i/o overheat

Nope. You got power steering on that ole girl?

 

[jamowers]

Re: 1982 120 hp mercriser i/o overheat

No I dont.

 

[chiefalen]

Re: 1982 120 hp mercriser i/o overheat

You got all the pieces out of the drive? You checked the long hose from the drive to the t-stat? You checked inside the t-state cover?

You got a flapper on the exhaust? Maybe it broke loose?

 

[jamowers]

Re: 1982 120 hp mercriser i/o overheat

I only removed the lower unit. The marina pressure tested the upper unit and it was fine vacuum and all. These flappers are in the upper unit right...or at least has to be pulled to see them?

 

[chiefalen]

Re: 1982 120 hp mercriser i/o overheat

Flapper is below the riser, below the rubber connector.If you have one. Look at the exhaust pipe, you have a pin that goes thru the pipe?

I would bet in a 1982 boat that never had a replacement riser installed needs one.

Probably needs a new manifold also. But if the boat doesn't go above 185-190 than it's ok.

Mine runs about 160-180. Never above 180.

You could finish out the season and over the winter check the riser and manifold.

 

[jamowers]

Re: 1982 120 hp mercriser i/o overheat

I will have to check it out on friday. It never got above 165, but I didnt run it too long. Thanks for the replies Chief!. Hopefully it will make it through the rest of this year.