WHAT TEMP SHOULD THE POWERHEAD BE ON JOHNSON 115???

[mrecho76]

Hello all,

So my troubles started about a month ago. I had overheating issues on my 1996 Johnson 115 and took it into a shop. They recommended starting with replacing the thermostat. The impeller was replaced less than a year ago. Then about a couple weeks ago, one of the cylinders had a piston ring fail. Powerhead was done.

I just had a remanufactured OBR powerhead installed, and the engine runs smooth so far. I haven't been on the water yet but I've run the motor with the lower unit in a huge container of water. One thing I noticed while warming up the motor, is that the right (starboard or taller) side was warmer to the touch than the left (port or lower) side.

I've done a lot of research online and some say that it's normal while others say that both sides should be roughly around the same temp. Got a temp laser gun to get exact readings and this is what I've found:

I warmed up the motor letting it idle and occasionally bringing it up to 1500 rpm. Ran it for 20-25 mins, checking the temp periodically. The highest temps reached were approximately 105 'ish on the port side upper and lower and 135 'ish on the starboard side upper and lower. I performed the temp checks by shooting the cylinder heads around the spark plugs.

So my question is, is this normal? Again, this is a brand NEW remanufactured OBR powerhead just put on, a NEW impeller just done as well, and NEW thermostats. Now from my understanding, the temps are within acceptable range, but why the difference? Should they both be around 105?

Any thoughts would be appreciated!

Thanks!

 

[emdsapmgr]

It's normal to have a little variance in head temps, but your variance is suspicious. Your powerhead is responding to the old stats you have on the exhaust adapter. That engine is responding to your existing two stats, one controlling temps to each head. The stats open at 143 degrees when idling. So, the powerhead should idle between 143 and 150 or (155 in the summer heat.) From your correct testing, I'd suspect that the port side thermostat is stuck open, causing cool head temps. While this is not an imminent "fatal" problem, you want to have both stats working the correct temps so that carbon does not accumulate around the piston rings-a long term problem on any cylinders running cold like yours are on the port head. I'd always recommend replacement of both stats after any powerhead overhaul/replacement. Ditto for the impeller. Also, when your engine gets up on plane, the two pressure-relief valves open in the stat housing-flooding the powerhead with extra cooling water. That's normal. Your head temps can go down perhaps 20 degrees from idle when on plane. Even more in a really cold lake. The laser temp gun is exactly the correct tool for checking.

 

[Faztbullet]

Hope your not trying to break it in just varying the rpm in a tank, it needs to be in gear and have a load on it....

 

[bob johnson]

did they rebuild the carbs, or just remove and replace onto the new power head???

I have a descrepency in temps on my 1995 115 ....and I have tried everything....at idle is is about 30 or more degrees for me...150 and 180....

I wonder if there is blockage in the water passages


bob