'90 Johnson 200 Cooling System - Expert Advise Needed

[metriccrescentwrench]

This problem is getting very strange. I suspect it's probably got something to do with some redneck engineering by a previous owner, but darned if I can figure it out. I'm hoping one of the experts on iboats can help.

I ran this engine for the first time a couple of weeks ago on the lake, after 10 minutes the overheat alarm sounded so I put the boat back on the trailer. (It had a new water pump, and water pressure was good). I found that neither vernatherm opened in hot water (I kept raising the temperature a little at a time up to 180F), and there was a lot of crud on the thermostat diaphragms and thermostat housing covers, but what I can see of the water passages looked good.

With new thermostats, new diaphragms, and clean housing covers I thought it would all be good. Ran it on muffs and found that starboard side was about 150 F as expected, but port side was only 105 F. I swapped thermostats and the problem seemed to follow the thermostat, so assumed one of the new thermostats was bad. I replaced the thermostat I thought wasn't closing with another new one (the dealer was nice about swapping it out for me), and still had the same problem. SO.... just for grins I kept the thermostats on the same side and swapped out the diaphragms - THE PROBLEM FOLLOWED THE DIAPHRAGMS, which doesn't make a bit of sense.

The only difference I see in the new diaphragms is a number stamped on them, one says "30", and the other says "47". Here's a photo of them:

A previous owner has removed the aspirator and water control valve associated with it. Here are some photos of the cooling system plumbing, I wonder if the experts see anything wrong with this:

Another view of starboard thermostat cover:

 

[Faztbullet]

Re: '90 Johnson 200 Cooling System - Expert Advise Needed

That aint even going to work as you cannot dump water off t-stat housing & diaphrams. The valve that was removed controls water pressure to the thermostat diaphragms(plugged line),when you opened your throttle it dumped water pressure off the diaphragms (which allowed the t-stats to completely open for maximum cooling) and power boost cooling was a joke anyway. Do the in-field FACTORY water mod and it will run great,just order the covers,springs and gaskets for a 89 70hp. You will lose the crossover hose and get some washers under them bolts on coils before you break the ferite internally...

 

[metriccrescentwrench]

Re: '90 Johnson 200 Cooling System - Expert Advise Needed

FINALLY, an explanation that makes perfect sense!!!

Do the in-field FACTORY water mod and it will run great,just order the covers,springs and gaskets for a 89 70hp.

I'll be using the existing thermostats (the "salt shakers") with these?

 

[Faztbullet]

Re: '90 Johnson 200 Cooling System - Expert Advise Needed

yep..

 

[metriccrescentwrench]

Re: '90 Johnson 200 Cooling System - Expert Advise Needed

Thanks.

I'd also probably never have noticed the lack of washers on the coils if you hadn't pointed it out, I'm sure fixing that will save me a headache down the road.

BTW, I'm looking at the boats in your signature, a 150 on a 13 ft Allison - HOLY $&!% Batman !!! I expect my '79 Checkmate project this engine is on to run pretty good when I'm done, but I don't think I'd have the guts to strap that one on.