overheating when going over 1500 RPM

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fish3227

Cadet
Joined
Oct 22, 2003
Messages
13
hey guys, i just can't seem to get this dam* motor working right. Merc 200hp carb 1997 outboard. I changed the water pump(including impeller), changed the stats,changed the poppet, and the darn thing still overheatd at high rpms and sometimes stalls at high rpms.Now the motor doesnt seem to get really hot, but my gauge says otherwise. If nobody else can help me fix this darn thing i think im just gonna throw it away. Its been to 3 mechanics also and still not working properly. Can i try running the motor without the poppet valve? to see if it works?
 
D

dilligafda

Petty Officer 1st Class
Joined
May 13, 2003
Messages
315
Re: overheating when going over 1500 RPM

When you took the poppet valve out, was there carbon on it? You may have an adapter plate leak that is causing areation of the cooling water. It's at least worth a look at the old peppet valve. And no don't run without it. You won't build enough pressure without it at low speed.<br /><br />Good luck!
 
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dilligafda

Petty Officer 1st Class
Joined
May 13, 2003
Messages
315
Re: overheating when going over 1500 RPM

Does it actually overheat or is it just indicated by the gauge. If you have access to a ray-tech gun or melt sticks, find out what the actual temp is.<br /><br />What is the water pressure when the engine overheats? If you see a pulsating, look for a leaking head gasket. If it is elevated, look for a lack of water flow and the engine making steam internally. If you see low pressure at 1500, normal would be around 9psi, look for a leaking poppet valve. Check that out and you should find your problem. <br /><br />Good luck
 
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