Overheating xr6 150 merc.

[Nitro13]

I bought this 1997 nitro with overheated motor (didn't know at the time) I replaced the heads w/ brand new ones.Replaced the impeller.w/complete new unit.Replaced all the head bolts. After the impeller replaced had 30 psi or more at 2500 rpm.Replaced the poppet valve.And inspected the impeller again.The alarm sounds 5mins after on plane. Stops when I slow down to idle after 3 mins.I also replaced both thermostats when I did the heads.I think I have some thing plugged I just don't know where to go digging.The boat runs great 125 in all cylinders,???? any help would be appreciated (Note before the impeller was replaced I had normal pressure readings on my pump gauge.I have put 2 new impellers in since no change).

 

[Texasmark]

Well pull the hose loose that goes to the poppet and run the engine long enough to ensure that water free flows through the hose once the block fills. Remove the poppet, connect it to the hose and crank and run the engine again above 2500 rpms with a good supply of water to the engine from the muffs. Last put the hose in the socket where the poppet fits and ensure that you have a generous amount of water coming out the LU. That should ensure that that route is clear and the valve is operating correctly. If no obstructions are found, look elsewhere.

Mark

 

[Nitro13]

Thanks for the help Whats LU.Im a car mechanic and new to boat lingo.

 

[Faztbullet]

Check to see if grommet fell/melted out of block behind poppet valve.Also check the rubber seals around t-stats . If it got hot enough to need new heads disconnect the oil injection as gear on crank is damaged and will fail....