1994 140 HP Johnson V4 operating temperature

[XcellR8]

What operating temperature should a 1994 140 HP Johnson V4 run at? I recently bought the boat/motor from a friend who hadn’t ran it last year. When we took it for a ride he mentioned the tell tale stream should be quite a bit stronger than it was although the boat seemed to run fine and no overheat alarm went off. The heads did feel pretty hot to the touch compared to my 1991 90 HP Merc. 3 cyl but he didn’t know how hot they normally got. I checked it with a temp gun on the muffs and after 2 min all cyls were around 150 degrees. The same test on my Merc produced around 110 degrees on all 3 cyl and the head was only slightly warm.

 

[Walker]

Re: 1994 140 HP Johnson V4 operating temperature

120 max at 5000 rpm's
125-150 at 900 rpm's

 

[XcellR8]

Re: 1994 140 HP Johnson V4 operating temperature

Thanx! It sounds like it's probably all right then (I did have one reading of 160 but it was only momentarily). I'm going to check the temps again when I take it for a ride to be sure. I know the stream that comes out of my Merc at idle is 3-4 times stronger and it definately runs a lot cooler which is why I'm concerned. I noiticed the Johnson has kind of a different system and the tell tell hole is a lot larger so I would alomost expect the output stream to not be as strong ... just wasn't sure what is normal for a Johnson V4.

Is it easy to hook up a temp gauge to this motor? Are the wires/sensor already there (I have a gauge that should probably work, just need to know where to connect it)? What temperature is the overheat alarm set for?

 

[Silvertip]

Re: 1994 140 HP Johnson V4 operating temperature

The existing temp sender is a simple snap switch that closes at a specific temperature -- it cannot be used with a temp gauge. You need a temp sender that works with your gauge. You would be well advised to replace the water pump impeller on this engine and any other engine you currently have or acquire in the future for which you have no idea when that service was last done. Just because the water pump is pumping water does not mean the engine is being adequately cooled. Stuck thermostats and bad poppet valves can contribute to overheating even with a a good pump.

 

[XcellR8]

Re: 1994 140 HP Johnson V4 operating temperature

The impeller is new. After we tried cleaning out the system with air and by running it on the muffs it didn't improve so I took it in to get the impeller changed along with a general check over. Got it back and there isn't much improvement in the water flow although it doesn't appear to be over heating other than the heads are pretty hot to touch (when compared to my 91 90 HP Merc). I checked the sensor cct. by disconnecting and grounding out the tan temp sensor wire on the starboard head and the alarm sounded so that part seems fine.

I took it for a ride yesterday and after about 10 minutes I shut it off and checked the head temps with a temperature gun. The highest reading was about 150 but most were 140-145 (I didn't do any WOT runs as the water was choppy). When I ran it on the muffs afterwards the tell tale started coming out after about 40 sec when the temps hit 140 and then all cyls seemed to fuctuate between 135-150 although at times the bottom cyls hit 160 (bottom left one had a momentary reading of 178 ... not sure what to make of that).

Some say the tell tale should start right away but this seems to coincide with the opening of the thermostat (wich appears to be at 140 degrees). I also noticed that the tell tell water gets pretty hot compared to my Merc. but I guess if this motor is designed to operate around 140 degrees it probably would. So does all this sound normal for a Johnson V4?

 

[Walker]

Re: 1994 140 HP Johnson V4 operating temperature

Some say the tell tale should start right away but this seems to coincide with the opening of the thermostat (wich appears to be at 140 degrees). I also noticed that the tell tell water gets pretty hot compared to my Merc. but I guess if this motor is designed to operate around 140 degrees it probably would. So does all this sound normal for a Johnson V4?

Not on your motor. The water passages in the block hold a lot of water and it takes a little while for them to fill up, and then the water will come out of the tell tale.