1985 mercury 50 4 cyl not peeing at wot

[deeps480]

I have a 1984 mercury 500 not peeing at wot. It pees fine at idle but once I get around half throttle it start sputtering and then completely dies out. Once the water dies out it will smoke out of the pee hole. Once back to idle speed it starts peeing g again.

The water is always hot to the touch even when just started.

It has a brand new water pump kit installed and 135 psi on all cylinders.

Any help will be appricated.

Thanks,

Dave

 

[deeps480]

Also I have back flushed the motor with no success.

 

[CharlieB]

Feel the exhaust side cover with the motor running, it should always be cool enough to put your hand on it all over the cover.

That cover holds water to cool the actual exhaust cover underneath it. If there is a hole corroded through the inner cover then exhaust gases under pressure of higher RPM can overcome the water pump pressure and prevent cooling water from circulating up and through the motor, you will see steam or smoke out of the P tube.

Exhaust cover bolts very often seize and can be very difficult to get out without breaking. Especially on an older motor. Rapidly tapping the head of each bolt with a small ball peen hammer while you gently try to turn it with a wrench may help loosen the corrosion on the threads. Once you get each one to turn slightly STOP, move on to the next. Once you get them all to move then again turn them out a little then back in, each time this will help further loosen corrosion until you can turn the bolt all the way out.

LOT of PATIENCE will save you from lots of broken bolts.

 

[deeps480]

I know it's been awhile but I pulled the exhaust cover today and found a small piece of the old water pump in there also the gaskets didn't look great. I have ordered new gaskets and am I'm waiting on them to come in.

It was a pain to get that cover off but no broken bolts and the exhaust plate has no holes in it.

I will update once I get it back together.

 

[Happybob52]

No Title

​I have a 1987 Merc. 45hp 50 Classic & this was what was wrong with mine. Same symptoms as yours. The housing is plastic & had melted, so the water pump was just forcing water around it under pressure. Unfortunately, this is a discontinued part, so you'll have to do some searching at salvage yards. That little $10 part ended up costing me $60. I hope this helps.

 

[racerone]

I would take a piece of aluminum material.---Drill the holes and file it to shape.--Better than the original.

 

[deeps480]

​I have a 1987 Merc. 45hp 50 Classic & this was what was wrong with mine. Same symptoms as yours. The housing is plastic & had melted, so the water pump was just forcing water around it under pressure. Unfortunately, this is a discontinued part, so you'll have to do some searching at salvage yards. That little $10 part ended up costing me $60. I hope this helps.

Thank you I will check that next if this does not solve the problem.

 

[deeps480]

I would take a piece of aluminum material.---Drill the holes and file it to shape.--Better than the original.

Are you speaking of the water flow holes or the exhaust holes in the powerhead?

 

[racerone]

I speak of that plastic piece at the top of the copper water tube !

 

[Happybob52]

I would take a piece of aluminum material.---Drill the holes and file it to shape.--Better than the original.

If I had a milling machine or knew someone, that's what I would have done. The plastic piece is counter bored for a rubber sleeve. It also has an offset where it has to bolt up. From what I understand, this part was used for a few years on several different models. Then Mercury went back to aluminum because of the melting issues.

 

[deeps480]

Just got done prepping to put it back together, just waiting on gaskets.

The plastic piece that you had melt on you are you able to access that from dropping the foot or do you need to remove the powerhead?

I'm still new to outboards and don't want to remove the power head unless I have to.

 

[deeps480]

If I had a milling machine or knew someone, that's what I would have done. The plastic piece is counter bored for a rubber sleeve. It also has an offset where it has to bolt up. From what I understand, this part was used for a few years on several different models. Then Mercury went back to aluminum because of the melting issues.

I will check into that piece next. The motor will **** fine at idle when at the lake and when in a barrel or on muffs it will pee while in gear even when reved up. I just won't pee while in gear under load

 

[Happybob52]

Just got done prepping to put it back together, just waiting on gaskets.

The plastic piece that you had melt on you are you able to access that from dropping the foot or do you need to remove the powerhead?

I'm still new to outboards and don't want to remove the power head unless I have to.

​The mechanic had to remove the powerhead. I'm at the time in life that I'd rather have someone else do my mechanical work. I'll change the lower unit oil, plugs etc., but other stuff, I leave to the pros.

 

[deeps480]

​The mechanic had to remove the powerhead. I'm at the time in life that I'd rather have someone else do my mechanical work. I'll change the lower unit oil, plugs etc., but other stuff, I leave to the pros.

Thanks for the information. I totally understand that. I just figured with this motor if I have to take it to the shop I might as well buy a new motor. I don't feel it is worth a thousand bucks.

 

[deeps480]

Ok I cleaned out the exhaust baffle area replaced gaskets and blew compressed air through the system. Started it up and let it run for about 15min. Water jacket area and exhaust plate was cool enough for me to hold my hand on(did not feel hot at all). Steady steam out the pee hole which was hot but I was able to hold my hand in the water with oil it being painful. Last thing the stream does not seem to get stronger when reving up the motor. Is that somthing to be concerned about?

I will take it to the lake this weekend to see if she is peeing under load.

 

[deeps480]

No Title

So I pulled the LU and looks like parts 10 and 11 are damaged. Would this cause hot water and exhaust in the cooling water?

Also I pulled the water pump and found old impeller under it that I cleaned out. I am ordering a whole new water pump kit and those parts.

Also I back flushed the whole system with the LU off and water comes out the copper pipe and around the exhaust tube is this normal?

 

[merc850]

10 and 11 are sealing parts for the exhaust tube and if exhaust does leak out it could heat up the waterpump.

 

[deeps480]

10 and 11 are sealing parts for the exhaust tube and if exhaust does leak out it could heat up the waterpump.

That's what I was thinking. Thanks for your reply.

 

[deeps480]

Ok I did the full water pump kit and exhaust seals and it is still hot when peeing. Does anyone else have an idea what could be causing this?

I guess my next step would be to pull the water jacket and look for debris and powerhead next?

 

[deeps480]

No Title

Found this little guy in the water jacket. Could this be causing the hot water?