Jonny 150 Looper Temperature Swings

[Fl_Richard]

I have 2 1995 non Ficht 150 Johnsons both have around 300 hrs. One recently in the last few weeks has been having dramatic temperature swings. Not so rapid that the gauge is bouncing around, more like at idle it heats up to around 160 and on a plane it dropps rapidly to around 120, stays there til I slow down then back up. Starbord motor is like a rock, always 140. Last August they were both rocks. Changed one of two thermostats, (didnt realize there were 2) Should I change the other or start looking at senders?<br /><br />PS has a good strong pisser and water out of pisser is very simular on both engines regardless of tempetaure readings

 

[Dhadley]

Re: Jonny 150 Looper Temperature Swings

Most temp gauges have only one sender so if your gauge is fluxuating then the problem could be on the head your sender is on. <br /><br />Is that the head that you changed the t-stat on?

 

[Fl_Richard]

Re: Jonny 150 Looper Temperature Swings

Simple answer... I dunno. Just looked through my clymer manual, found temperature switches relating to S.L.O.W. one on each side. Cant find any mention of the water temperature sensor or it's location. <br /><br />I know where it is on my Chevy and I dont have a manual for it.....<br /><br />Can anyone help with this?<br /><br />Thanks<br />Richard

 

[DHPMARINE]

Re: Jonny 150 Looper Temperature Swings

160 degrees is too hot for the port engine.I'd start witha new water pump,and go from there.Or you could get a wax stick or a electronic temp reader and try that way. <br />Also,I would replace pumps on both motors as regular maintenance,as well as both thermostats on both engines,as well as their seats.<br /><br />DHP

 

[walleyehed]

Re: Jonny 150 Looper Temperature Swings

I'm just a punk here, but it appears to me if it goes down to 120 on plane, not 140, we have a T-stat issue, but then again,idle -high temp, plane speed-low temp points to waterpump....<br />That being said, I just repeated the above posts for the most part.....I'll shut up now....<br />Besides T-Stats, does this engine have relief valves as the earlier V6's had???

 

[Fl_Richard]

Re: Jonny 150 Looper Temperature Swings

For anyone interested, I just tore this unit apart. Found one severely cracked vane in my impeller. Havent repaired it yet but I'll let you know the final outcome. <br /><br />This was a 5 vaned impeller so it was only about 60% effective i figgure...