Intermittent overheat 98 Johnson 115 (J115ELECM)

[Faztbullet]

The problem is the t-stat housings are also the poppet valves and the old ones look sorta like the new style. You need to get a copy of the TSB 2313 as it addresses high speed overheat on 1997 and early 1998 V4/6 60degree engines and t-stat kit #435587, and you remove the insert in the head with the new style bodies...

 

[V153]

If you run these motors in say 60 deg or warmer water. I'm not so sure thermostat's are all they're cracked up to be.

Do be sure to use the 'poppet' valves.

Down here sawing the thermostat off the base is perfectly acceptable. That or use a SS fender washer to restrict the flow.

 

[Faztbullet]

The t-stat housing is the poppet valve,they are not like a crossflow t-stat.....

 

[midsized johnson]

The t-stat housing is the poppet valve,they are not like a crossflow t-stat.....

That's what I have in there. I also have a grommet inside the housing that the backside of the thermostat seats on. Is this supposed to be in there with the newer thermostats? I can't find any info on the TSB, but will call a local dealer and see if they have any info on it.
Appreciate all the input.

 

[bob johnson]

I would lean towards the notion you have a lean issue at higher rpms... your water flow being sufficient enough at lower rpms to keep the motor cool...it would be better if you have a temperature gauges, one to each head. Then you KNOW what the temps are all the time. I actually have the opposite issue, I have one head get warm (180degrees) at low rpm and idle...but once I get past 2500 rpms and the water pressure reaches 20 psi...the engine cools nicely all the way to 6000 rpms.

you should prop your motor to peak at 5800 rpms or so... I always have hated those restrictive thermostats, but the flow THROUGH them isn't your issue...because the water pressure pushes the whole thermostats OFF THE SEAT, and water flows AROUND the t-stat!!!......so you are getting mega water...but still over heating...seems like it is something other than water cooling...bad friction, lean condition.... I don't know enough about motors to guess beyond those choices..

good luck

bob

 

[midsized johnson]

No Title

Bob, my thinking was that by eliminating the T-stats as the possible cause, if I had a lean condition, no amount of water flow would keep the engine from getting hot and I would still get an overheat alarm at upper end. So far, since grinding off the thermostat caps, it hasn't happened, even with the motor jacked all the way up in the tunnel running over extremely skinny water.

 

[bob johnson]

Bob, my thinking was that by eliminating the T-stats as the possible cause, if I had a lean condition, no amount of water flow would keep the engine from getting hot and I would still get an overheat alarm at upper end. So far, since grinding off the thermostat caps, it hasn't happened, even with the motor jacked all the way up in the tunnel running over extremely skinny water.

if you are getting an alarm, you are up over 220 degrees!!!!!!!!.....does the motor go into SLOW mode???

you have to turn the motor off as well as let it cool to disengage SLOW mode.....in SLOW mode you cant run the motor higher than 2500 rpms..

I took out my t-stats a few years ago to trouble shoot...you cant even maintain 5 lbs of water pressure....it just flows so easy... it seems if you had a lean condition that bad, youd have a sneeze.. just turn out the high speed mixture screw one or two full turn.... you can easily turn it back in if you make even turns....see if that cools the motor...


bob

 

[midsized johnson]

Given the time since last water pump servicing, I went ahead and pulled the lower unit to install new kit. Lo and behold, no exhaust cover!!! The impellor housing and water tube inlet on top of the housing are both partially melted. The unit itself was still pumping with good water pressure, but I now feel like at higher end, I was pushing super heated water into the power head.
My next problem is figuring out which exhaust cover will work. Luckily, I found both type covers (short and long) used, on ebay, from the same seller. They said they'd let me return the one that doesn't fit.
I can't believe the knucklehead that did the last water pump job for me didn't tell me it was gone! I even asked him about the exhaust soot that was on the both sides where the midsection and lower unit mate up. He said something like, "they do that sometimes." Maybe he needed one???