1987 Mercury 45hp 50 classic thermostat

[Happybob52]

I'm having some issues with my 50 Classic cooling system. It's not peeing right. After a minute or so at high rpm, the stream stops and it just starts spraying steam(or exhaust) with very little water. I had the impeller replaced a couple of weeks ago. They did not change the housing or wear plates, saying they looked in good shape. I was told, in another forum, to replace the thermostat & pressure relief (pop it) valve. I cannot for the life of me, find these parts on the motor. I know a thermostat should be located at or near the top of the head and the valve should be near the bottom of the motor, but where? I don't have a clue. I've been searching on-line manuals, you tube and the world wide web with no solid results for this particular engine.

Can anyone help me?? Any help is greatly appreciated.

Thanks, Bob

 

[goldstem]

Quite sure no thermostat or poppet valve on that motor that year. if a new impeller didn't do it, you have bit of diagnosing to do.

 

[mixerjv]

Definitively no thermostat or poppet valve on that engine (the 44cu in 4 cylinder Mark 58-Merc 500- Merc 50 Classic 50 45hp and the Merc 40)

Perhaps the tube that goes from the lower unit to the engine is missing a rubber sleeve or is bent and not seated right.

 

[Happybob52]

Thanks guys. I appreciate your help. I got the same info from a couple of guys on another site.

mixerjv, the mechanic that replaced the impeller did mention (after the fact), that the tube seemed a little loose.

I'll be pulling the lower unit myself and doing some checking. I know for sure that I'll be doing the whole water pump kit. Not just the impeller.

Does anyone know where I might find an on-line parts diagram?

Thanks again, Bob

 

[mixerjv]

Go to the official Mercury Parts Catalog (google) and make sure you put in your serial number (DON'T search by year/model with older engines like this) and it should come up.

 

[quicktach]

Check for plugged cooling system; impeller key problem. loose - worn - unconnected sleeve at top of water discharge tube. impeller in backwards...plugged water intake

 

[Happybob52]

Well I found the problem. The water inlet tube seal housing is trashed. It's just a plastic housing that holds the little rubber seal for the water inlet tube. It bolts to the exhaust/adapter plate under the power head. And it apparently got hot & melted enough to not seal tight. I've had a couple of mechanics tell me that it's a fairly common problem. The really bad news is that the part is not made anymore. So now I'm on a quest to find a used part. Talk about finding a needle in a haystack! I thought I found one at a salvage yard in Oklahoma, but when the woman found it, she told me "It's a little melted on one side." I told her "Ma'am, that's why mine is no good. It's melted on one side." From what I understand, there are other year models that used an all aluminum part that will interchange with my engine. But I can't get a straight answer as far as which ones.

Any help is greatly appreciated. The part number is: 79799

 

[racerone]

Your location is ??

 

[Happybob52]

I'm in Lexington, SC, near Columbia.

 

[HelixBoat]

Did you ever find that part? I am on the same
Quest.

 

[GA_Boater]

Old thread.

Closed.