Johnson 1989 140HP Overheating

[pwheatla]

I have a Johnson 140 HP Model A- J1400TLCCM (1989 year) running premixed fuel rather than separate oil tank. I have an overheating problem. The alarm sounds after about 3-5 minutes operation at between 3000rpm and WOT. Have a good tell tale stream at all times and have recently replaced the thermostats. I'm running a mixture of 50:1 (2%). Appreciate any ideas as I have recently had it serviced identifying this problem but it still remains.<br /><br />Thanks Phil

 

[Walker]

Re: Johnson 1989 140HP Overheating

When was the last time you put a waterpump kit in it??

 

[pwheatla]

Re: Johnson 1989 140HP Overheating

Haven't in the two years I have had it. Could this be the problem if the telltale is streaming strongly?

 

[emdsapmgr]

Re: Johnson 1989 140HP Overheating

It is possible that the thermostat plate hole may be plugged. There is a platic-type plate sandwiched between the mid section and the thermostat housing (cover). The thermostats sit in this plate. There is one (perhaps two, depending on model) small hole. These must be open. Permits hot water to drain to the backside of the thermostat, heat them up and cause them to open. If it is plugged, the engine will overheat.

 

[Walker]

Re: Johnson 1989 140HP Overheating

Phil, change the water pump, use a complete kit not just an impellor. Is this a saltwater motor.<br />You are describing a higher rpm overheat. At those RPMs the popit valves should be opened bypassing the thermostats, unless yours are malfunctioning. <br />The water deflectors under the cylinder heads may be swollen and obstructing water flow too. I bet they have never been replaced.