I think I messed up when I replaced my thermostats - advice sought

[Gas Giant]

Engine is a '78 Johnson 85HP, 85ML78C.

Two weeks ago I replaced the thermostats, the plastic diverters and the springs on this engine, largely due to not knowing when it was last done. (Did the water pump impeller too). The engine hadn't given any indication of overheating, but I don't want any surprises when I'm out on the water.

I fired the engine up today and ran it for a short while. It was "peeing" as normal, but I was also getting a huge amount of water out of the starboard exhaust relief hole (I think that's what it is called). I was getting a little bit out of the port side, but not enough to concern me.

I also noticed that the starboard side cylinder head was hot....well not hot as in overheated, I could touch it without burning myself, but the port side was cool to the touch. Thinking that maybe that the port side cylinders weren't firing, I unplugged the top cylinder. The engine idle audibly changed, and I audibly shocked the **** out of myself. So yeah, its firing. Not wanting to do that again, I grabbed my inductive timing light to check the bottom cylinder, and it flashed on that one. (For giggles, I checked the port side too, and it flashed on both cylinders as well).

Since the engine obviously isn't supposed to run with water gushing out of weird holes, I shut it down.


Cliff Notes:
Replaced thermostats/diverters/springs/gaskets (had a LOT of difficulty getting the assembly back in.....)
Made sure the small holes in the plastic housing in the thermostat assembly were clear
Huge gush of warm water from starboard exhaust relief hole when running, hardly any from port side
Engine pees normally when running, pee stream is cool
Starboard side cylinder head warms up, port remained cool to the touch
Ran engine for 5-10 minutes approx.

So, does it sound like I screwed up when I installed thermostat assembly? I tried putting it in like the diagram in my manual, but that sucker ain't easy to install!!!! Any tips on putting it back in if I have to pull it out?

If not, what else could cause this? Engine compression varies between 115-120 on all 4 cylinders (I forget which ones were which) so I doubt I have a head gasket problem.

 

[emdsapmgr]

Re: I think I messed up when I replaced my thermostats - advice sought

The telltale funtioning is a side issue. It shows the impeller is working. The main issue is that you have a hot side to the block. I'd be suspect that something inside the stat housing did not go back together correctly or that the stat on that side is stuck closed. I'd probably pull the stat housing off again and check things. I'd also switch the stats from side to side for test reference. See if the other side overheats when you reassemble. The cyl head temps should be about 140-145 shen warmed up-as measured with a laser temp gun. You might want to rent one for a day from your local auto parts store. You may find the factory exploded parts diagram helpful as a reassembly reference: epc.brp.com. As difficult as your stat housing is to work on, most of us would rather work on yours than a bubble back stat housing....

 

[Gas Giant]

Re: I think I messed up when I replaced my thermostats - advice sought

I forgot to mention I was also looking at the exploded diagram on the boats.net website.

I think that one of the diverters shifted when I was putting the assembly back in, based on what I have read elsewhere. I'll pull the assembly back out this week and check. (Should be easier now that the center bolt won't be stuck)

Also, when you guys reinstall these, do you use any gasket sealer on the gaskets, or just put them in as is? My old ones didn't appear to have any gasket sealing compound on them when they came out.

I'll also recruit a helper to help me reinstall them, and post the results for future searches.

 

[archcycle]

Re: I think I messed up when I replaced my thermostats - advice sought

I also noticed that the starboard side cylinder head was hot....well not hot as in overheated, I could touch it without burning myself, but the port side was cool to the touch. Thinking that maybe that the port side cylinders weren't firing, I unplugged the top cylinder.

Check the port side it might be stuck constantly cooling. Just pull it all out and re-seat it and fire it up again. Sounds like the starboard is good it ought to be quite warm but not dangerous to touch at idle.

 

[Sixmark]

Re: I think I messed up when I replaced my thermostats - advice sought

If you really want to test the T-stats to see if they are working properly, instead of taking it apart and then putting it back together multiple times, just remove the T-stats and put them in a pot of water and heat up the water to the temp at which they should open (within a few degrees + or -) if it doesn't open then you know it's bad.

 

[Gas Giant]

Re: I think I messed up when I replaced my thermostats - advice sought

Sixmark, I'll test that. They're new thermostats, but these days that doesn't mean anything!

 

[Gas Giant]

Re: I think I messed up when I replaced my thermostats - advice sought

I got the assembly out. Turns out when I installed it, the spring on the port side plastic relief valve shoved the relief valve and its rubber grommet all the way through the valve body and both were sitting on the thermostat cover. Not quite sure how that happened, but hopefully the parts will be reusable. Starboard side was ok.

It seems odd that this happened on the port side, yet it was the starboard side exhaust relief port that was gushing water, but it may seem weird due to my not entirely understanding this engine's cooling system.

Haven't tested the thermostats yet, but I will tonight hopefully.

Will also post finished results when I get the assembly back on the engine. Nothing worse than reading a thread with a problem similar to your own, only to find that the thread has no conclusion!

 

[Gas Giant]

Re: I think I messed up when I replaced my thermostats - advice sought

Thermostats tested good in a pot of water.

Got the assembly back in today. Also went ahead and cleaned out the carbs and put in new float valves in both as the bottom one was leaking fuel when I primed the bulb.

Fired her up, and she runs better than ever - both heads are evenly hot (using a "touch test".....lol), she's peeing normally and not gushing water from the exhaust relief port, and not overheating at all. Ran it for about 15 minutes on the hose with no signs of trouble.

So it was the poppet valve (or diverter, as I called it in previous posts) after all. Thanks to all who replied.