94 mariner 200hp overheating

[Dboii]

Hey what's up guys hoping one of you can maybe help me out. I have a 94 200hp mariner that's overheating. I changed impeller, impeller housing with gaskets, thermostats, and head gaskets but it's still overheating. Any idea what's causing this? I also cleaned all the water jackets from cylinder head from salt buildup and ran engine without thermostats and water is coming out of thermostats holes good. Appreciate any help thanks

 

[havoc_squad]

What about the poppet valve that dumps extra water in the engine/exhaust to cool it at high speeds?

I would suspect that, timing is way too high/ out of spec, obstruction like water impeller piece, lean condition causing clyinders too get excessively hot, or water pickup tube not seated fully/correct are all possibilities worth checking.

Running lean or poppet would be my guess if the overheat happens going above 1500 rpm but stays cool during idle.

 

[Dboii]

What about the poppet valve that dumps extra water in the engine/exhaust to cool it at high speeds?

I would suspect that, timing is way too high/ out of spec, obstruction like water impeller piece, lean condition causing clyinders too get excessively hot, or water pickup tube not seated fully/correct are all possibilities worth checking.

Running lean or poppet would be my guess if the overheat happens going above 1500 rpm but stays cool during idle.

Thanks for replying man I'm gonna have to check the timing and also might be running lean who knows. It overheats while being idle too so I'm thinking it might not be poppet valve. You have any idea how to check if it's running lean? Would cleaning carbs help with running lean? I'm gonna have to do a bit of reading too figure this out meanwhile I appreciate any help

 

[CharlieB]

when water pump, T-Stats and poppet valves all check out fine there is one thing that can drive us nuts until we find it.

Some V-6's blow the base gasket under the motor to the base. The water inlet passage is right next to the exhaust. Gasket failure here allows inlet cooling water to dump straight into the exhaust.

Repair involves lifting the motor from the mounting plate. Checking surface flatness and replacing the base gasket.

I often take a center punch and make a line of 'dimples on both surfaces between the inlet water passage and exhaust. Then lightly run a flat file over my dimples to make sure none stick up too far. Wipe surfaces with acetone so no hand oils anything to prevent a perfect seal. Coat my new gasket is lightly as possible, just the very thinnest smear of good grade silicone and let it dry thoroughly before assembly. And I mean thin smear, barely enough that you can tell something has been put on it. DRY at least an hour. Putting it together wet it is too slick and can smash out,, squeeze and tear. Patience is key.

 

[Faztbullet]

The word SALT is the problem as passage ways still could be clogged, areas eroded and allowing to much water flow,seats that have eroded and not sealing and base plate rotten...