1986 110HP Johnson Thermostat Problems

[mrmamiller]

I have a 1986 110HP Johnson Which has undergone repairs in the last 2 years and now I have the port side bank running cold. I am monitoring temps with IR gun and attached thermocouples (both agree with each other). The starboard side goes to 140 deg F and holds, the port side runs around 110 deg F. I am running the motor in the driveway on muffs. I just got the boat back from having the thermostats replaced because of an overheating problem on the starboard side (haven't had in in real water yet).. When the engine is first started, water comes out the holes just above the anti-cavitation plate. I'm pretty sure that water only comes out here after the thermostats have reached temperature (at least that's the way mine has run in the past). Prior to taking the boat to the dealer for the overheating problem, I noticed that water was coming out of these particular holes prior to the overheat condition as well. Note: This motor was pulled apart a year ago and had a new piston in #1 cylinder and new rings/honing around. I didn't have any temperature issues prior to this work. So, initially I'm thinking stuck-open thermostat on the port side, but it was just replaced. Due to the fact that this motor was pulled apart recently, I also wonder if something was left out (or left in that wasn't supposed to be).

Any ideas? Thanks.

 

[oldcatamount]

Re: 1986 110HP Johnson Thermostat Problems

It's possible the deflectors were left out of the water passage ways in one of the heads. There's only one way I know of to find out if that's the case, and that is to remove the heads and have a look. I think I have a link to a parts diagram for your motor below. It's from www.marineengine.com and you'll see the deflector there (#10).


http://www.marineengine.com/parts/j...+&+Crankcase+-+All+Models+Except+110tlcdf

 

[mrmamiller]

Re: 1986 110HP Johnson Thermostat Problems

Oldcat,

Thanks for the info. I guess I never considered the deflectors, but since the motor was ripped apart, that's a consideration.

I ran the motor again for about 15 mins on muffs, and this time the temps were a bit more balanced, but it took up to 10 minutes for equalization. I shot the block/heads with an IR gun and there were no real hot spots, so I think I am ready for an in-water test (but I can't use the IR gun when I'm on the water.

There are some issues with when/where the water comes out of what holes that are different than before rebuild, so I think I'll address that after being on-water.

Thanks, Mark