How to check for a damanged thermostat

[sigeforrest]

I have a 89 Johnson 50 HP VRO and it is cutting out at 1500 rpm. I have already replaced the gas, tanks, fuel line, fuel filter, spark plugs, and cleand and rebuit the carbs with new kits. After doing some research, one possible reason may be a damaged thermostat. I have the OMC manual but I cannot find anything about how to check/replace the thermostat. Has anyone ever checked or replaced the thermostat on one these motors? <br /><br />Thanks,<br />Forrest

 

[Silvertip]

Re: How to check for a damanged thermostat

Cuting out at low rpm may be the engine going into "SAFE" mode which limits engine rpm by interrupting the spark. So the first thing you need to determine is IF your engine is overheating. Does the tell-tale show a good stream? If not, its water pump replacement time. Has your hot horn sounded? (Does the hot horn beep momentarily when you turn the key on?) If not it needs to be fixed as it may be indicating a VRO problem as well. Why bother "checking" a thermostat. You need to remove it to check it so why not replace it and be sure it works. They aren't a major expense. Does the engine actually feel hot when this happens. If you have an OMC operators manual there wouldn't be any service information in it. You need a service manual. If you indeed have an OMC service manual, everthing you need to know about troubleshooting and thermostat replacement is in it.

 

[ezeke]

Re: How to check for a damanged thermostat

Thermostat cover is at the top of the cylinder head above the spark plug. <br /><br />Before you open it you should pick up the parts at your dealer. You will want a new gasket and thermostat - small money and a good investment.

 

[sigeforrest]

Re: How to check for a damanged thermostat

I have the OMC Service Manual for this motor. The manual states that i must remove the crankcase and lift the crankshaft from the cylinder block to remove the thermostat components. Is it possible that I am reading this wrong? Or are the "components" different from replacing the actual thermostat?

 

[reeldutch]

Re: How to check for a damanged thermostat

i think you are reading it wrong.<br />listen to ezeke the tstat is in the cylinderhead.<br />good luck

 

[DHPMARINE]

Re: How to check for a damanged thermostat

You might be reading it correct,if you are reading in the powerhead dissassembly section.<br /><br />But basically the thermostat is under a cover screwed into the upper part of the cylinder head.The service manual should show an exploded view of this.<br /><br />DHP

 

[rickdb1boat]

Re: How to check for a damanged thermostat

Looks like it's behind a large screw-in "plug" at the top of the cylinder head on that model...

 

[Silvertip]

Re: How to check for a damanged thermostat

This is a ten minute operation standing in back of the engine in your driveway.