1980 Evinrude 150 Hot Horn

[Striper68]

Need help with 1980 Evinrude 150 V6 Crossfire. Starts and runs great after about 4-5 mins at WOT 6000 RPM hot horn sounds. Kill engine or return to low RPM and horn quits in about one min. VRO removed long ago runs premix. Can run all day at lower RPMs only happens above 3500 RPM. Impeller and head gaskets recently replaced as well as new set of Champion OEM plugs. Used IR gun to measure temps starboard head 145 degrees, port head 175 degrees. Any sugestions on what or where to check next?

 

[HighTrim]

Re: 1980 Evinrude 150 Hot Horn

You may have a water blockage going to the port bank, since they should run cooler than the starboard side because of the way that water flows through the motor, usually around 10 to 15 degrees cooler. Id remove the lu and 1 t -stat at a time, running compressed air up the water line to ensure there is no blockage, also backflush the air down from the t stat housing to the water line, and check that the t stats are not clogged or stuck . When the heads were off, did you inspect the water deflectors?

 

[ezeke]

Re: 1980 Evinrude 150 Hot Horn

Newer complete waterpumps are better than the old ones and may help.

Thermostats may be clogged.

The cooling circuit can be cleaned and may need it, especially if the engine is used in muddy water or in salt water.

The waterpass deflectors often need to be replaced.​

 

[Striper68]

Re: 1980 Evinrude 150 Hot Horn

The work was performed by the previous owner of this engine. I guess I will be checking the condition of the deflectors, tstats, and for any blockages. Thanks for the quick reply.

 

[emdsapmgr]

Re: 1980 Evinrude 150 Hot Horn

If you are going to be in the thermostat housing, be sure to check the pressure relief valve on the port side. If they get overheated, sometimes they deform. Could be that one is stuck/not functioning properly. It's supposed to open at high speed to flow more cooling water. If one is a problem, you'd notice it at high speeds and that's what you are dealing with.

 

[1730V]

Re: 1980 Evinrude 150 Hot Horn

If you are going to be in the thermostat housing, be sure to check the pressure relief valve on the port side. If they get overheated, sometimes they deform. Could be that one is stuck/not functioning properly. It's supposed to open at high speed to flow more cooling water. If one is a problem, you'd notice it at high speeds and that's what you are dealing with.

Agreed. The relief valves and deflectors are suspect. Might as well replace the stat's while you're in there.