82 merc 200 runs hot

[prolinews]

I have 200 v6 that is driving me nuts it's a 2.0 liter. When I bought the motor it had been in a small electrical fire I replaced all wiring stator trigger power packs etc. the motor cranks easy and runs great ,but if run it hard for several minutes it runs hot. The motor is on a heavy 20ft center console with t-top . I run a 15 prop it only turns up about 5000 if the tach is accurate about 35mph gps. I have a new water pump and housing, took the manifold apart to see if it had a blockage pulled heads everything looked great good compression on all cylinders the timing is right what could be the problem? I don't need a rocket just something I can run about 20 mph for more than ten minutes. Would smaller carb jets help? or am I overlooking something. It always has a good water stream from tell tale I can run for days at low rpms with no problem .

 

[CharlieB]

Re: 82 merc 200 runs hot

Two things to check out. These are the two most common hard to determine problems with the V6

First the water pump lower housing, the SS plate must be flat and seal well with the both upper and lower housings so's NOT to suck air at speed when the drive is on a plane and the pump is above the surface level of the water.

If that all checks fine then the second possibility is a cracked or split gasket between the exhaust adaptor plate and the engine allowing the higher water pressure at RPM to leak into the exhaust passage, bypassing the motor and reducing cooling at RPM. It's a PITA to have to lift the powerhead but at least it isn't an expensive fix.

 

[frenchhunter]

Re: 82 merc 200 runs hot

I had the same overheating problem for 5 years with my blackmax 200hp.I lifted the powerhead yesterday and i think i found the problem. The lower exhaust plate gasket was broken and let pass cooling water directly into exhaust tube.....I made a new one myself with garlock 900 and reassembled the powerhead.The job was easyer than expected.I am hurry to try my rig tomorrow. If you have similar problem and you replaced water pump,t-stats and poppet valve without amelioration,don't hesitate and take a look at this point. I will let you know if my problem is solved after my next fishing trip. Hope this help

 

[hkeiner]

Re: 82 merc 200 runs hot

I you don't solve your problem by rebuilding the water pump, I would suggest that you consider installing a water pressure gauge. Watching the changes in PSI readings at various RPMs will provide a good indicator of what the possible problem may be. A gauge is easy to install and not very expensive.


http://forums.iboats.com/attachment.php?attachmentid=26806&d=1240515681

 

[frenchhunter]

Re: 82 merc 200 runs hot

I made a trip with my boat this morning and all my overheating problems are gone.Thanks to Iboats members for the helpfull hints . Now, i may trust my merc.....

 

[hkeiner]

Re: 82 merc 200 runs hot

Never mind...

 

[prolinews]

Re: 82 merc 200 runs hot

I will pull the power head this weekend and see and replace the gasket for sure. I've been told my motor was dry stacked does that have anything to do with the gasket going bad?

 

[frenchhunter]

Re: 82 merc 200 runs hot

May be . Mine was stored for 6 years before i bought it. The old gasket i removed was very dry and brittle.If your motor is a 2.4 litre like mine ,the gasket needed is p/n 27 99177 2. it was impossible for me to obtain one rapidly,so i made one myself.

 

[Chris1956]

Re: 82 merc 200 runs hot

Drystacked means that the exhaust system was modified to allow the exhaust to escape above the waterline. You should see some holes cut in the midsection, if it has been modified for a drystack.

Did you test your thermostats? They should open at 140*. Have you inspected/replaced the poppit valve?

 

[CharlieB]

Re: 82 merc 200 runs hot

Good call Chris on the poppet valve.

I was just rereading his post about the electrical fire which would have been right above the poppet valve, heat could have damaged it.

 

[prolinews]

Re: 82 merc 200 runs hot

new thermostats was using galvinized washers to see if it made a difference, it didn't cleaned the poppit works fine new water pump impeller housing plates etc. I cant wait until sat to pull the powerhead. A cracked or bad gasket almost has to be the problem. I've been puttin around 3yrs trying to figure out what was wrong with it. It does not have aftermarket exhaust ports on the mid section. I had a bass boat like that once, loud as rip and always got the attention of marine police.

 

[CharlieB]

Re: 82 merc 200 runs hot

Are you SURE that WOT timing is set correctly?

Friend has also been chasing his tail for a couple of years,since buying a 150 XR2, I finally talked him into rechecking everything, from square one, and found WOT timing wayyyy retarded. All better now. He's still saying "D'oh!!!!"